Friday, October 20, 2017

Radio Frequencies

After reading this blog, I decided a Tektronix 496 was a reasonable spectrum analyzer for me to look at RF's for my tuners and antennas, FM MPX signals, digital SPDIF signals, and audio frequencies when I want to see up to 100kHz.  The lowest center frequency is 1kHz, and the highest frequency is 1800 Mhz.  Obviously it's no good for wifi or things like that, and I would have liked to view wifi signals, BUT the price of even used scopes goes up $1000 or more for spectrum analyzers with 2Ghz and above response.  Those microwave scopes are still in heavy demand by professionals.  There's much less professional concern nowadays with mere VHF and UHF.

While I'm slowly (very slowly) making progress debugging my Acoustat speakers (each new test requires 1-2 weeks "to be sure" because the problem is intermittant), I've decided to indulge my long running desire to get involved with...radios of all kinds.

I was blown away by the capabilities of the 1-30Mhz Icom IC-7300 and have one of those on order (due to recent rebate promotion, they were sold out so I'm still waiting for mine...but will have the assurance of a fully updated unit and still get the rebate--I hope).  I'm also planning to get CB radio (always wanted one of those) and a scanner.  I've started buying and setting up antennas for each, and will get them all professionally grounded with ground rods and bonded ground back to the main house ground rod.  Also finally I'll put up a rooftop antenna for FM, but it won't be my APS-13 which has been waiting in it's box for more than 10 years.  Sadly that's still to complicated because I refuse to have any antenna actually on the roof, so I need side mounted mast or tower, which I continue to think about how to do.  Professional antenna installers aren't interested in such things...they'll attach tiny HDTV antennas to your chimney or roof, and those are the only options they're interested in anymore.  I may get some hams to help me with my big antennas someday.  But first, I'm planning to become ham myself, with some smaller simpler antennas.  For FM I'll be using either a Godar FMDX 100 or Magnum Dynalab ST-2, which I can simply tack on to fascia board on the side of the roof at the peak (no massive tower or mast required).

One of the essential things for installing and comparing antennas is an antenna analyzer.  I could have used my Spectrum Analyzer if it had the tracking generator, but it does not.  So, instead, I got a Sark-110, which is a tiny miracle, which gets great reviews.


Monday, October 2, 2017

Poltergeist

Sunday night I played KPAC for 6 hours without shutdown.  Then, sometime after I let the cat back in, and was getting ready to take a shower, I went out to turn the amplifier off.  The amplifier was already off.  The cat was not far away in the living room.

Perhaps the cat rubbed or pressed the relatively soft touch button in front of the Krell.

I think a cat could learn to do this.  I know my cat loves to rub against the front of the Krell, though also has learned that I don't like it.  But, the fact that I don't like it makes it something the cat might do to get back at me when I'm not paying enough attention.

I know now this hasn't caused all of the shutdowns.  Because several have occurred when I was right in front of the amplifier listening to music.  (That hadn't been the case until a few weeks ago.  Until then, all of the shutdowns occurred while the amp was playing for background music, which is how I listen to music 95% of the time.)

This did not fit the now familiar pattern of shutdown within 60-120 minutes, that happens about 50% of the time.  It "might" be a different mechanism.

It certainly didn't explain the two shutdowns this weekend (1) with the Krell playing F-26 through Lavry as source, and (2) with the Krell playing F-26 through Sonos, both which involved playing in both channels, since in both cases, the cat was out.

The 3rd and final test was playing right channel through the now-right (formerly left) unmodified speaker with the NOS interface.  That didn't cause a shutdown for 6 hours, and by then I was strongly believing this speaker and channel were OK, it was the other one (that seemed to have groove in the variable resistor, and has the upgraded capacitor outside) that had issues.

I'm not taking that guess as disproven yet, it *could* be the cat or some other "3rd" mechanism this time.  But from now on I'll need to control for the cat possibility.  I've figured out I can leave a polycarbonate DVD-Audio case leaning in front of the amplifier, hiding the button, and meaning that in order to press the button the cat would need to knock over the plastic case, so it would also show that it had been done.

Here's a short list of remaining open hypotheses:
1) Damaged variable resistor in one or both speakers.  (Could explain some, or all shutdowns if both.)
2) Damaged big capacitor attached to case of modified speaker.
3) Damaged factory capacitor in NOS interface speaker.
4) Amplifier changes during last two repairs.  (This would now be the biggest bitch, since the amplifier has already been checked out for this problem by the factory, I'd have to have a specific shutdown causing protocol for them to find problem, or chances are they never would.)
5) Now running on two AC circuits (a change made earlier to prevent shutdowns, but possibly causing some too).
6) Teflon speaker wire (another change made to prevent shutdowns, seemed to work for one day).
7) Change to F-26 causing some inaudible spurious output that causes shutdown even over Sonos (most shutdowns recently caused by FM, since it's too hard to keep music playing without using FM).
8) Cat pressing power button somehow, to play with me (could explain some, but not all).
9) Burst of RF energy from something.  (I had turned off buglight on Sunday night, so that didn't cause Sunday night shutdown, but it could have caused many previous shutdowns.)  This could explain shutdowns with no other explanation.
10) Deteriorating AC power contacts.



Sunday, October 1, 2017

Another unexpected result

I'm playing KPAC-FM, the classical music station, and it is delightful.

The F-26 tuner is hooked to a Sonos Connect input, then the digital output of that very same Sonos feeds a Belden cable (terminated by Blue Jeans Cable with Canare "true 75 ohm" RCA's) carrying SPDIF digital to my Tact RCS 2.0 Preamp.  Thus is an "analog source" converted to digital for processing by my DSP's for crossover and EQ and time delay.

Actually, for high class sources, I prefer to digitize through my Lavry AD10 digitizer at 24/96.  The Lavry feeds a Geistnote AES cable to the Tact RCS.

However, a long time ago, back when I had all the equipment in front and was playing the Krell, long before the Capacitor Service in March 2017, I was playing a Pipe Dreams show on KPBS, using the Lavry instead of Sonos to digitize the output of the tuner.  And the Krell shut down.  That is the very first time I remember such an incident.  I figured right then that there was a motorboating DC or high frequency burst that is not nice.  And digitizing through the lowly Sonos somehow suppresses it.

Perhaps it's just a matter of 96kHz vs 44.1kHz sampling.  Or it could be transparency to DC, quite likely the consumer friendly Sonos has a steep high pass keeping DC out of the system, whereas perhaps the Lavry goes deeper in the low Hz.

I resumed the Lavry connection, praising it as far superior, in May 2017.  And that was actually the first time a shutdown occurred since I got the Krell back from Capacitor Service.  It was a few days before the high power incident that blew speaker fuses and which I still believe was responsible for a fundamental bit of destruction that has been causing many, if not all, of the shutdowns.

Right then, I figured the problem playing the F-26 through the Lavry was AC power limitation, with the subs demanding current at the same time as the amplifier to meet some demand caused by a presumed low frequency burst (which I've never heard...since the amp just shuts down).  The Krell must be allowed to scale up it's AC power consumption fast to meet any higher bias plateau level the computer with in it demands.  If there is any glitch in scaling up the power consumption, it will shut down for "inadequate AC power."  Actually, this happens when the rail voltage regulators, which are rare in any power amplifier (but there are a few other very high end amplifiers, such as the Mark Levinson ML2, which have this feature), run out of regulator margin...which is precisely because the AC hasn't kept up.

Anyway, it is quite possible that the problem tracking down the problem with amplifier shutdowns is that there is more than one process involved that causes the shutdowns.  One might be that running the F-26 through the Lavry simply creates a problematic signal.  The other one, which I believe must have been caused by the high power accident, has yet to be determined, but as of the beginning of this weekend was hoped and believed to be the LF transformers inside the Acoustats.

Well, so I was thinking Sunday morning as I started playing KPAC through Sonos, with the LF transformers in the Acoustats disconnected.  This was surely the issue, more than one cause of the shutdowns, and by avoiding the F-26/Lavry input, and disconnecting the bass transformers, I had isolated both of them.

And I was so sure of this, I started writing this blog post after it had been playing for 90 minutes.

And then, there was a shutdown, a shutdown that could not be explained by either theory.

I have noticed that sometimes, also, that Sonos blanks out for about 1-2 seconds, or maybe it's the tuner blanking out.  Perhaps that happens when Sonos is suppressing some DC from the input or something.

Anyway, this result doesn't disprove the idea that I should avoid the F-26/Lavry input.  That was known to be problematic in the distant past.

But for years and years I played the F-26 through Sonos without shutdowns.  So that is most likely the "new" problem I am trying to find.

At this point, sadly, I'm out of good theories.  Back to there being a malfunction in the Acoustat attenuators???

I concede it could also be a problem with the Amplifier, though the amplifier was just checked out at the factory.  But I won't make any headway with that until I have a consistent explanation of the problem.  I may need to measure voltages in and out.  Which would be another major challenge...I'd have to build a custom attenuator to protect my measuring recorder inputs.


Saturday, September 30, 2017

Help, Part 9. Character building opportunities.

I strongly dislike the obsession with "simplicity."  I think this is very freedom limiting, and has no essential basis in what people can actually hear.  Sure, have a 3 way system is more complicated than a 1 way system.  And so on.  But done properly, a somewhat more complicated system can have better performance in the ways that are most meaningful to a particular audiophile.  Ways that I'm interested in, such as having bandwidth from the infrasonic to the ultrasonic.

However, there is absolutely no doubt, that a more complicated system is more difficult to set up properly, AND to keep working.  So, it's a challenge, and that means that a complicated system that works, let alone works well, is a testament to an audiophile's talent and perseverance.  And so it's a character building exercise.

Sadly, the "keep working" part has been my primary focus since I apparently damaged something in May of 2017, and started having amplifier shutdowns.  Tracking down the true problem or problems here has certain been a test of my perseverance.

After trying to stop the problem with various tweaks, such as new less capacitive speaker cables (made of hand twisted 12 gauge silver plated PTFE coated wire) for several weeks, I noticed that the problem had occurred when I was playing through the right speaker only, but not the left speaker only, so did a further series of tests pairing up each speaker in each amplifier channel, figuring it might be one speaker, or one channel, but hopefully not both.  I figured the problem could be either a shorting transformer or other part in one of the speakers, or a malfunction in one amplifier channel.

I determined that either speaker playing on the right channel would cause a shutdown, but either speaker playing on the left channel would not.  So, this suggested that the amplifier, which had recently had capacitor service costing $1800, had developed a faulty channel.

I sent it in for repair (as always, itself a fairly challenging exercise) and Krell found a problem and fixed it and sent it back for free.

Well, after that repair, now BOTH channels could shut down with either speaker.  I could have thrown in the towel at this point, sworn never again to use a Krell amplifier, and so on.  But actually, it dawned on me that shutting down is exactly what the Krell is supposed to do when there is a speaker short.  The the final Krell repair was actually to restore this correct behavior to both channels.

And so back to what had been highest on my list after the tweaks didn't help: the speaker transformers.  (In fact, it took several weeks of testing before it occurred to me it even might be the amplifier.)

I had in fact tested the high frequency (HF) transformer in the most suspect right speaker back toward the end of June.  I disconnected the HF transformer, and, playing with no highs and a very recessed sound, and there was still a shutdown.

I hadn't believe the low frequency (LF) transformer would have a short for several reasons, the first being that I highpass the speaker signal at 100 Hz, taking a big chunk out of the low frequency current in the  transformer, and second that it's a big honking transformer that looks like it could handle anything, whereas the HF transformer is this little tiny thing.

It was right about then that I narrowed the problem to an apparently malfunctioning amplifier channel (actually, it was the channel that was operating correctly, and the other channel which was not shutting down was the one that was not operating correctly).

So I never got around to testing the LF transformers.  Until I got the amplifier back and it then seemed the most logical thing to do, again.

But first I decided to tackle something which had long bugged me, and would be less expensive to fix, I cleaned the HF power resistor connection which had turned green in both units.  I took a day to thoroughly clean away all the green and make sure the contacts were making good solid contacts (which, in one channel, it might not have been).

Sadly that did not stop the shutdown.  Or as usual it worked for one day, and I was elated.  Then, the next morning, I got a shutdown again.

By this time, I had told my story in the DIYAudio AcoustatAnswerMan blog, and the AcousatAnswerMan himself, Andy Szabo, said he had not seen the HF transformers go bad.  He strongly believed the LF transformers were at fault, is that had always been at the root of intermittant speaker shorting.

Well, I then had a very busy weekend, so the hopefully final really big deal would occur.

Disconnecting the LF transformers was easier than I expected.  They simply unplug with a slide connector.  But then you have to insulate the loose end.  I figured out how to first wrap the connector in non-sticky plastic (to keep it from getting sticky), then electrical tape, attached very thoroughly to the wire insulation.  Then the whole thing is wrapped around the now essentially disconnected 1 ohm resistor.  One one side, I further protected it from coming loose with a nylon tie wrap.

And so, I started to play on Saturday September 30.  The most difficult source: my F-26 tuner digitized through Lavry AD 10 at 96kHz.

It was playing great for over 4 hours.  By this time I was giving myself high fives again.  This was it, I am sure, the LF transformers have an intermittant short.

This was also an opportunity to do some other things.  For one, I was hearing the HF transformers more directly, and now I think I might have been able to hear the old electrolytic in one speaker, vs the new large polypropylene in the other.

I turned the balance all the way to the left channel, which now has the speaker with the polypropylene cap.  It was sounding cleaner, purer, I thought.

To be sure, I turned the Tact to Mono mode, so I was getting the whole signal.

It continued to sound clean.

Then, 5 minutes later, playing only through the PP capped speaker and the left channel, it did the impossible again, for the 200th time.

It shut down.

Maybe I just can't play the FM that way...which I had never in fact done for very long before May.  I vaguely recall getting shutdowns playing FM that way, so I went back to using a more bandwidth limited Sonos connection to the FM tuner.

So that will be the test tomorrow.



Sunday, September 24, 2017

Help, Part 8

Science, Magic, and Gambling


Now, I think, this is where some of my thinking, anyway, begins to join the dark side.

Science speaks not in terms of absolute truths, but probabilities.

Now, this might not help you much when the probabilities are six nines against you.

It depends on the downside, whether I'd consider taking another roll.

Some of the things we know about how well we can extract the information from a musical event or audio are pretty certain, others not so much.

The detectability of out-of-band information may be in the lesser assurred category.

For example, our ability to detect ITD is conservatively estimated at 20 microseconds, equivalent to 50kHz frequency response.  Some are claiming detectability of ITD at the 1 microsecond level.  The actual importance of this to imaging may be easy to overestimate, since ITD is only one thing we use, and we use it mostly at low frequencies.

Anyway, audio does present a smorgasbord of scientific questions you may or may not consider partly open, along with many other kinds of questions, including those in the domains of engineering and psychology.

If you want to believe that this or that is audibly better, when it contracts what I consider well established science or engineering, who am I to stop you?

I suppose, if I were on a consumer crusade against unnecessary audio technology, I might.  But, I'm not.  I don't see excess audio technology as not a major threat to human society or the environment.  And to some degree, the flaming of certain cults, such as those involved in preserving older equipment, might be beneficial.  Audio generally is low impact as compared to many human activities, even many of those related to "appreciating nature."  Mind you, if you are concerned about such things, I recommend such bandaids as I apply myself: recycling (through legitimate electronics recycler) the least resellable equipment, or donating, rather than trashing it, and using green electricity--otherwise I might feel guilty about my endless pursuit of Class A amplification.

Now, I think it's best to have a realistic assessment of the posssibility your tweak might help.  But there's no great need for that.

Audio itself is disbelief in the apparent reality, that you are listening to a music event, and not a contrivance of electronic engineering.

So this is another way of saying, that audio is at least party a "magical" event, in which we fool ourselves, or allow ourselves to be fooled, much as with stage magic.

So, if fooling oneself is essential to the greatest appreciation, why not fool yourself a bit more?

Why not believe that the latest trick "is" going to do something, despite serious evidence that it would not?

If it helps keep you going, who am I to say that's wrong.

And in fact, I'll egg you on a bit.  I'll say that low probabilities are not zero probabilities.

You could be right, though I would not bet on it.

I'm busy covering a few of my own bets.



Friday, September 22, 2017

Help, Part 7

The 'Philes.

Long ago, about the same time as one audiophile friend lost his high frequency hearing while doing all the metalwork required for his very massive Leach amplifier, another audiophile friend derisively dubbed those he considered more interested in building equipment than actually listening to music, "Build-o-philes."

Having built and modified some equipment myself, and having been an avid reader of Audio Amateur, I found this somewhat insulting.  So, I coined my own term for people who endlessly like to make arguments about audio and audiophiles, "Argument-o-philes."

Though I felt then, and still do, that however people want to play, subject to the usual constraints, is well and good.

And, being an "audiophile" means only that one is "enthusiastic about audio," and not that one necessarily has fancy audiophile cables, or even listens to music.  Not that I'm saying anyone doesn't.

That was where this kind of argument stated long before.  The newly rising subjectivist audio reviewers wanted to distinguish themselves from the prior (and continuing) generation of objectivist "meter readers" by claiming the mantle of loving Music.  And, of course, music is this holy thing, that brings us peace and joy and saves our souls.  Of course it's what Audio is about, it's what Life is about!

So hence, even in the pages of the gearhead oriented The Absolute Sound, endlessly reviewers would claim the banner of being Music Lovers for themselves, in some cases in opposition to being Audiphiles.  "Oh, we're not Audiophiles, we're Music Lovers."

Now, I have known several Music Lovers who were not audiophiles.  They were not interested in equipment At All.  They had handed-down or thrift store or box store "record players."  They had lots of records, indeed costing far more than their equipment.  They were easily distinguishable from Audiophiles and would not even have heard of magazines like The Absolute Sound. Given the potential of introducing audiophilia nervosa, I would hesitate to even attempt to make people aware that there is anything better, unless they are asking for it.

Of course, there is little wrong with being that kind of music lover, especially today, when, contrary to much opining, good sound can be cheap and easy.

But there is nothing wrong with being a build-o-phile, an argument-o-phile,  measure-o-phile, or whatever.

Even if there isn't much value in getting harmonic distortion (and hence IM) down farther and farther below the 1% level where it can reliably be heard, it's an interesting challenge, possibly rewarding,
and potentially of considerable value to society.  Low distortion amplifiers are needed in virtually all technology.

And, virtually all humans love one kind of music or another.  I don't mean to suggest otherwise, but merely not to sanctify it as the ultimate source of all human joy and satisfaction.  It's good, but it's not everything all the time.  And I don't think it's fair to denigrate people who have interests in technical things, though the rise of subjectivist audio reviewing often seemed to do that.

I acknowledge being an argument-o-phile myself, though I'm also in many other 'philes.



Thursday, September 21, 2017

Audiocorder and other stuff

For decades, I used timer recording systems of various types to record FM radio programs, just as people use VCR and their modern equivalent HDR to record TV programs.

My Nakamichi 600 had a timer start mode which causes the unit to start recording when power is applied.

My Nakamichi RX-505 has the same feature, and I have used that as recently as a few months ago to record FM radio programs.

I even had a Sony all-in-one music center (a small box) which had the feature, which prior to 2006 I used to record daily radio programs for playback in my car.  It had been fairly hard to find that unit.  However, after 2006, the march of "progress" eliminated the cassette player in my latest car.

This was a huge step backwards for my personal connectivity.

While there were supposed to be digital alternatives, I found none so convenient.  For example, in order to use podcasts, I needed to connect my iPod to my computer every day and fumble around with iTunes.  For various reasons, this often didn't work, and it was ALWAYS more of a hassle than simply popping a cassette into my all-in-one recorder had been, and finally I gave up.  If the internet radio didn't specifically make a daily "podcast" you couldn't just record a particular program at a particular time.  It seemed to me there is a conspiracy against timer recording.

Perhaps there are timer recorders for digital radio now, I haven't looked.  More recently I use smartphone apps to listen to specific programs I like....however this doesn't help if no one has created a suitable app for the program you want to listen to (and there are several programs like that for me).

Anyway, here is Audiocorder, which lets your Mac operate like a timer recorder for audio.

Then, using an extra program they suggest, you can get it to record internet radio also.

Now, stepping somewhat back from High Fidelity, another interesting recordable thing out there is Pirate Radio.  Some of these are on FM because virtually all listeners already have the required FM radios. But most pirate broadcasters are probably sitting in the less intrusive/detectable/complainable regions of HF (say, 6.7Mhz).  I can pick that up with my new General Coverage Receiver (at least, as soon as I get the antenna set up).   While FCC often shuts down pirate radio stations in the FM band (they say, they only do this if someone complains, which is probably accurate) I doubt they have much time for the non-amateur parts of the HF bands and many pirate stations there are legendary.

Here's one list.

And here's another.

HF Underground is showing a bunch of loggings from today.

And of course there are fully "legal" HF broadcast "shortwave" shows also, but books are filled with info on that (including one book I just bought).

I suspect few radio amateurs would risk their own hard won licenses running a pirate radio station.  But I've known hams tell me right away that pirate radio is among the best stuff to listen to on HF.




Sunday, September 17, 2017

Help, Part 6

Around 1970 Saul Marantz was interviewed, and I remember hearing it on a Los Angeles radio station.

Marantz said he went a different way than others of his generation, and that was what led him to perfectionist audio equipment.  By following his own path, he discovered new things, created a successful company, and opened up a new arena for others.

(I recall the introduction said Marantz "invented" high fidelity--it appears to have been invented many times, and still nobody knows what it is.)

Anyway, for what it's worth, that idea of following your own path seemed right to me then and ever since.

Just because "all audiophiles" are supposed to do this or that, I not only feel fine doing something differently, I feel it is good.  Everyone doing the same things would mean little new discovery.

Saturday, September 16, 2017

Help, Part 5

To EQ or not to EQ

The argument I have often heard advanced against deliberate equalization is that it introduces errors in the phase response, or the time response.

What is not understood, is that when deviations from uniform (aka flat) response occur, they have already introduced errors in the phase response and the time response, and that using EQ to correct these deviations actually restores all three at the same time: the frequency response, the phase response, and the time response (and this is because they are all, essentially, aspects of the same thing...the signal itself).

Now, this is generally true, which means in some cases it may not be true.  But in specifically what many people believe is the most troublesome case, room EQ (to uniform response), famous TAS audio reviewer (and Professor of Mathematics) Robert Green claims that room response deviations from linear reflections, which most are, are minimum phase, and hence are corrected by the inverse deviation.

So far from being horrible, correct EQ is beneficial to the phase and time.

Now this is not to exaggerate the importance of phase response.  Large volumes of research show it is not audible to surprisingly large rotations.  Anyway.  In all cases like this, existing research doesn't prove it won't be audible at this or that time.  But, if you want to prove you can consistently hear it, it's probably going to be hard enough that you wouldn't bother.  So, if it so hard to hear, it can't be too horrible, can it?  Not to say the challenge of getting perfect time response, hopefully w/o sacrificing too much else, and appreciating it as one can, can't be a fun endeavor on it's own.  But existing knowledge doesn't suggest it's worth sacrificing many other things, notably the frequency response, for.  In most cases.

Then there is the matter of what you might call, deliberate non-uniform response.  Now, those indeed will be adding time and polarity deviations, along with the frequency response variations.  But this is the natural way these things occur, and are generally accounted for in only describing the frequency response (not the "horror" of deliberate EQ in particular).  So if you were, say, achieving the same result with some tweaky infidelity, exactly the same and not added distortion or whatever, your tweaky response correct would have the exact same effect on the phase and time as a deliberate EQ system--preferable a digital EQ but some high end analog EQ's are truly high fidelity also (such as the Cello Pallete).

Now, before the days of digital EQ, analog EQ's had lots of practical issues, including but not limited to distortion causing devices.  It was rare to find a really good one; before the Palette, I'm not sure there was.  Now, with digital input and digital output, a cheap digital one can be as perfect as the 24/96 audio it puts out (in the case of the Behringer 2496) when you use full digital I/O.  The distortion is many zeros below the decimal point, the noise level is better than -144dB.  Jitter does not appear to be any higher in the output than in the input...it does not appear to add to jitter (nor does my whole chain of processors and converters)--and once again not to exaggerate the importance of jitter, but just saying.  And of course, precisely the filter you wanted, with no pole out of place.

Designers of loudspeakers have long understood this, and the importance of compensating for driver impedance and response in the crossover is done.  This is just another form of deliberate EQ, often with somewhat precision-limited parts, but often very carefully considered designs ("engineered"). And correcting the driver response corrects the phase as well.  However, most crossovers do introduce group delay and some time dispersion.  Virtually all scientists, engineers, and manufacturers do apply more crossover than the minimum: just lowpass on the tweeter, the 1930's standard.

The primary issue involved here, IME, is loudness uncompensated listening comparisons.  Without compensating for the difference in efficiency, a more minimal crossover will play louder, and hence have a large tendency to sound better.  If drive power can be increased without issue, the less efficient corrected response, done correctly, would be preferred.  Not that there aren't limits as to how far this can be done without diminishing dynamic range.

Since the scientists, engineers, and manufacturers generally do level adjusted comparisons (though perhaps within a desired range of efficiency) they find the more complex crossover to sound better.

Subjectivist gurus do not do level matched comparisons, so the more minimal crossover sounds better.

The same issue, typically combined with sighted expectation bias and other biases, explains a lot of tweako beliefs, from power conditioners (maybe not a bad idea, but not with the massive benefits claimed), expensive audiophile cables (which if they do anything at all to the sound is probably destructive to simple well made cables), lack-of-feedback, single ended, and NOS.

In every case, if there are actual changes, people may find they prefer them, for highlighting this or that, but perhaps also what people find they prefer in casual testing might not over the long term be appreciated as well.

I think it's very risky to try to achieve fidelity through infidelty, other than correctly determined and deliberately applied EQ and possibly out-of-band filtering.

But, it's your roll.

Now, why does loudness, even trifling amounts, make things sound better?

Because it increases our auditory S/N, and opens up a far greater amount of information.

Now one thing to be clear is we never fully absorb the information of even the most limited presentation.  So why do we need more information?

Because it gives our auditory system a greater sample to choose from; it opens up patterns that previously were hidden by noise (most often...household ambient noise).

Now, there are limits to this that vary a lot, and playing so loud as to cause compression (not to mention clipping) may be undesirable (especially, compression in your own hearing system).  And as I posted before, actually avoiding current or voltage limiting may be far harder than people recognize.

Which is another thing.  Unless you have very high efficiency speakers, or even so, you may need far more power than you realize.  In practice, little spikes of peak power are required up to alarming amounts.

Sanders' estimate was 500W for typical dynamic loudspeakers.

That may be a bit high for typical dynamic speakers.  I would think 100W for kiddie speakers, 200W for serious speakers, and 300W for inefficient high end speakers.

But there I am, giving advice again.

I see John Curl describes his friend Dick Sequerra's Metronome speakers as "kiddie speakers."  They're small, with small drivers, though possible do require more than 200W amplifier.

Anyway, they take clean impulse response to an exteme.  The crazy looking tweeter and weird woofer do actually deliver very clean impulse response, hence the name Metronome.  However, the frequency response is way out of whack, and finding the right "location" may be problematic too.

This is the example of sacrificing much to get the perfect impulse response, an ultimate tweako goal (since the serious scientists, engineers, etc, don't consider it THAT important, though never discounted entirely, and there is some room for doubt).

They do have amazingly well focused imaging, though not all people like that either.  But many people who try them for awhile find they dislike some aspect of this approach.  I'm sure I couldn't stand it at all, though it might be interesting to have a pair for an imaginary magic show.

So that's what they are.  Stage magic equipment.  A good description also of high end tweako stuff which is less well engineered.



Help, Part 4

My friend Tim has intensely studied many transistor and tube characteristic curves for decades now.  He's a very technically and mathematically astute.  He's also done some test building over the years, but mostly his beliefs come from studying the curves and the mathematics.

He says now that push pull BJT* amplifiers work best in Class AB, not Class A.

Of course this flies in the face of everything I've ever read, heard, or thought about, and my most prized audio machine is a Class A amplifier, because I've long been a fan of Class A amplifiers and my belief that they are best for electrostatic speakers.

He agrees it flies in the face of standard and conventional thinking, but insists that nevertheless it's true.  His argument is that the "cutoff" distortion on one side precisely works with the changes on the other side to produce the lowest distortion at some particular AB bias.  Class A doesn't get this benefit, and produces higher distortion.

He's been wrong before, so he could easily be wrong this time.  My suspicion is that it either misses other factors, and/or

But, if he's right, and in many cases even if he's wrong, it's quite possible that Nelson Pass's Threshold amplifiers (which were BJT, he switched permanently to MOSFET after leaving Threshold) were sub-optimal.  The attempt to eliminate cutoff, Tim affirms, would produce higher distortion than the correct Class AB, and would therefore produce higher distortion than necessary, and at higher operational costs.

That's certainly true of some other of Nelson's designs, such as many devices in the single-ended Aleph era, and many of the First Watt designs.

Is this a big deal?  That through charisma or whatever Nelson sold higher distortion amplifiers than necessary?

Firstly, I suspect all the Threshold amplifiers all had distortion sufficiently low, and with sufficient reliability, and relative high power and current into most loads, to be considered fully High Fidelity Amplifiers, such as there is no respectable evidence that people can hear differences between.  So the "loss" to the users of Threshold amplifiers is nil, by the audio objectivists very own standards.

They've been loved, held their value, etc, etc.

So, that's fun, entertainment, and playing music.

Secondarily, when the actuality doesn't really matter, the only thing that does matter is the story.  The story says lower distortion, greater PRAT, or whatever.  The story makes you feel good.  The increased distortion is irrelevant, in most cases, even in many extreme cases where people just seem to groove on the distortion.  Minimum distortion I would generally look for, myself, as much as I can afford.  But if other people like other stories, other presentations ever, that's their thing, at least while it lasts.  I think, in the end, as little as possible distortion, combined with the greatest flexibility (the equipment is supposed to let us Play music, not have Music imposed on us)

I believe many of the beliefs that modern distortion reducing methods create bad sound are myths, having perhaps vanishingly small examples, and none where proper engineering has been done.

But there are actually many different circuits, it's hard to say we have an "optimal" circuit as such, and if we don't have an optimal circuit, then we don't have an optimal class, and so on.  Furthermore some things may create more or less distortion than other things under some circumstances, and have the reverse be true under others.

In fact, as is well known, people love the higher distortion circuits like SET's and transformers for various reasons.  And since this is about fun, not Accurate Reproduction, that's fine, for them, as long as they continue to do so.  And much as I might think it would happen, many people are sticking with one of many higher distortion than necessary paths.

We don't hear distortion very well anyway.  It's the frequency response under load we hear mostly.  People are finding or not the EQ they want.  Some people fear EQ.

Many like me fear this is an expensive, and even more than that, difficult and ineffective way to get very much EQ.  But if someone thinks it works for them, it works for them, fine.

I have actually experienced a "solid state" "dryness" (in a malfunctioning Citation 11) which couldn't be eliminated with (it's very own) EQ.  That happens when you have higher noise and IM than necessary.  You can't EQ that away.  But EQ works quite well for most other things.  When we have digital sources, we can have distortion and noise free EQ, which provides exactly the alteration needed or desired.

EQ lets me easily and precisely play with how things are played, and that's become very important to me.

(Tim variously prefers and not prefers MOSFET amplifiers in Class A.  He has most often said MOSFET amplifiers require very high bias to be in their most linear region, and for practical reasons (would it require liquid nitrogen cooling?), nobody ever does that.  But he may be softening on the bias levels needed to make MOSFET preferable to properly biased Class AB+ BJT's.  I think there may be other factors and ways of looking at the situation.)

Friday, September 15, 2017

Help, Part 3

I have a very simple answer to the question "What is Audio" and I believe my simple answer quickly refutes those stubborn audio objectivists like Peter Aczel and Floyd Toole who say that "Audio is Engineering, Music is Art."

Fun.

Audio is not just music reproduction  Audio is fun, and fun is the ultimate principle that it's all about!

And so of course it is true.  Audio is a hobby that audiophiles passionately follow, and just like all other hobbies, it's ultimately about having fun.

Then I suppose it could be argued that professional audio is different, professional audio is the engineering which serves the creation and reproduction of music.

But even there, and especially for Audio, if your job isn't fun, as many say, you should get another job!  (With the slight disclaimer nowadays, "if you can.")

I'm glad we've gotten that straightened out.

The creation of fun is not something that can be engineered, though the relevant engineering should applied where it needs to be, or it's not going to be fun very long, if at all.

But indeed it does help that we have Entertainers like Nelson Pass*, one of the more fun people in Audio.  He's a very good engineer also, it's easy to see.

(*Pass described himself as Entertainer in a recent Stereophile Interview.)











Avoiding clipping requires high power

Roger Sanders of Sanders Sound Systems (a leading manufacturer of electrostatic speakers today) has a white paper on amplifiers.  He says transistor amplifiers are better for electrostatic speakers because the low impedance outputs can drive the capacitive load, which he characterizes as 1 ohm at 20kHz, with more extended frequency response.  And, because it's easier to get high power in transistorized amplifiers.  He claims most audiophiles have undersized amplifiers, and when they hear amplifiers as sounding different that is because they clip differently.  But the solution is not to find the amplifier that clips better so much as finding the amplifier that has enough power to never clip.

Interesting, and pretty much in line with my thinking.

I don't think, however, I voltage clip either my "200W" (actually something like 500W into 4 ohms at clipping, as published in Audio review) Aragon, or my "300W" (actually something more like 900W into 4 ohms at clipping, as measured in Stereophile review) Krell very frequently.  In fact I'm pretty aware of clipping points because I know the max output of my DAC (which drives the power amp), the digital attenuation I'm using at a particular time, and the digital output level.  (However, there's some wiggle room between what the nominal output is and peak output...so I'm not totally sure how this works out...actually scoping the output for clipping like Sanders suggests is not a bad idea and I've often thought about doing it, just never gotten around to it.)  I believe I generally do not clip either of these amplifiers based on the levels of signals they are receiving, however I do not know.  However, I come far closer to clipping than most might imagine.  At the max levels I listen to, I'm right under those levels by just a db or two.  And that's with 900W into 4 ohms on tap.

He does mention also current limiting.  Current limiting and clipping are somewhat different.  I might be getting more current limiting than I know about, though it's doubtful there is very much since both amps are capable of more than 60A peak currents (IIRC the Krell is around 100A).

Sanders claims that average listeners with 90dB efficiency dynamic speakers in typical listening rooms need as much as 500W on tap to avoid clipping.

That's way more than most people think.  I'd guess more like 200W but I haven't examined this by doing the measurements Sanders has.

Meanwhile I find (in sighted testing only) the Krell to sound better.  Less current limiting perhaps??? I believe that the Krell has flatter output at 20kHz into the Acoustats than the Aragon.  I've seen this in acoustic measurements but never measured it exactly.  It may be because the Aragon is a low feedback amplifer with a damping factor of only 450 below 1kHz, whereas the Krell is a high feedback amplifier with damping factor of 900 or higher and extends to higher frequencies (though, this is not a Krell specification and I can't remember where I saw this measured).  The Krell has zero loop feedback, but the output stage has it's own local feedback (drivers and outputs), as well as more bigger transistors, and power bandwidth to 300kHz.  The Aragon is a more traditional design with loop feedback, but less than 2dB of loop feedback, and power bandwidth of 60kHz, but still lots of transistors for low impedance despite low feedback.

A friend of mine who originally didn't think much of the Aragon has been studying the circuit in great detail, and decided it's actually very good.  The low feedback fits perfectly with this design, and is probably close to the Baxandall recommendations (either very low feedback, or high feedback, but not middle feedback).

He also points out that the Quad ESL-63's have a very amplifier friendly resistive load, not like the capacitive load Sanders describes.  This was part of the ESL-63 delay line design.  However, that is unique to Quad ESL's as far as I know.





Thursday, September 14, 2017

Help, part 2

[An ongoing exploration of the audiophile scene.]

Nelson Pass concedes the audio objectivist debate in the objectivist's own terms.  "The amplification problem is solved," he says in September 2017 Stereophile Interview.  But then he precedes in terms very much as in this blogsite I have argued against the hard form of audio objectivism.  He says nobody needs the amplifiers he has produced, or even the circuit designs he has patented.  People can get along fine with other amplifiers and designs.  He describes his job, instead, as an entertainer.  Some people are entertained by his work and his works, and he works to serve them.  I am one of those.

That's pretty much what I've said against Aczel and Toole, who claim exactly that audio is mere engineering which serves art.  Audio itself is art, which partly serves music, but also party serves other things.

Now, for sure mass manufactured products are engineered products.  But there is plenty of art in a manufacturing concern.  And if run well, the product is art, this is well known to all now.

A lot of audio, though, is more personal, much more personal than opening a box and plugging one thing in.

I haven't scratch built anything major since 1982, when I built a tube type preamp with separate power supply.  It sounded great, and bested an Audible Illusions around 1986.  But I lost the massive power supply on my move to Texas, and haven't used it since, as well largely preferring solid state equipment.

I might tinker, such as the modifications I made to the Aragon tape selector circuit which I use in my living room analog racks.  Selections are now unloaded and totally isolated, except for ground.

And there is the ever evolving programming of my DSP's.  I strongly prefer total manual control to automagic EQ.  But that itself is another decision.

Every decision is a form of participation.  Even going to an audio specialist, who plays two things, and asks which you like better...that decision is a substantial participation.

Though, if all you do is make a purchase decision, and have specialists take care of everything else...then it's not very much DIY.  But that's pretty rare among the proletariat.

Most audiophiles are very involved, it's at least a part time preoccupation, not even counting the seriously listening to music part.  I make no pretense that I am not a gearhead, not interested in the vast details...or that I don't collect too much, the latter perhaps being the greater crime.

Some seem to become manufacturers of major equipment on some scale.  Sadly one of my best audiophile friends got massive hearing loss during the metalwork involved in the production of his own Leach amplifier.  And then he hated the sound of the amplifier.

By far most people are surprised by the degree that we imagine, rather than perceive, reality.

People may be scientists, designers, and even engineers, and not get this.

I get it.  I can freely "hear" something to be better.  Hearing is never the same twice, and it's only partly related to the information at our ears anyway.  So, a typical sighted audiophile test, which I myself have done a lot (but generally avoid, I prefer to do no upfront auditory testing, "long term" testing only, and that has not been the source of any of my numerous errors) means nothing.

I won't say it's impossible that there is this unknown X factor, which makes amplifiers sound different, not related to the things we know like frequency response into speaker load and IM and absence of voltage or current limiting.  Possibly there is some "simplicity" "charm" or whatever.  But very dedicated testers have done serious tests for 50 years, a nothing has been confirmed.  All other claims have been debunked.

A friend--the one who took his Sony 3200F to audiophile meetings to show up the big boys, was convince he had the trick.  Just listening for himself, and with some luck, he had found the answers.  Get a 3200F!  He couldn't explain why it sounded better.  His mantra to this day remains that measurements don't matter.  (It seemed strange to me, though, that he says measurements don't matter, and yet by some chance he chose a good measuring amplifier.  Seemed unfair somehow.)

Most people in most of these gathering seemed to agree his amplifier sounded best.  By his account, all of them who seriously listened believed the 3200F better.  Of course virtually all of these tests were sighted, none were level matched (he had an argument against that...it cannot be done because there is more than one frequency to match), so as a proof that the amplifier problem has not been solved, they are inadequate in all ways.

I wouldn't think that I or anyone could have such luck, so much better than everyone else, that I could ever stumble upon The One Answer like that.  Instead, I think his entire enterprise was a repudiation of amplifier differences, rather than the proof of one person's excellent luck and taste.  The amplifier problem was solved in 1968, if not before.  The Sony had modern specifications, such as 0.1% THD and virtually flat frequency response.  Far from proving that measurements don't matter, his experience is more evidence that once measurements get good enough, people can easily be swayed one way or the other, merely by one's presence, or tendency to adjust the volume slightly higher for one's preferred amplifier.  People including oneself.

It is known that we are NOT very good detectors of harmonic distortion, and in particular of the kind most audio circuits produce.  It may take 1% or more to hear it on music.  In short term tests, meanwhile, we are far more sensitive to small differences in frequency response, 0.1dB is roughly equivalent to 0.1%.  In fact, in large part, we may be hearing the harmonic distortion by the effect it has on frequency production.  Bass distortion is often heard as louder bass.  But, the same nonlinearities which produce THD also produce IM, which we are reasonable sensitive too, it's just harder to define a single measurement for.

Anyway, most modern amplifiers don't vary much in frequency response into most loads.  You have to go to tubes, generally, to get something significantly different from a $300 receiver.  Or something very culty.

[Electrostatic speakers, and sometimes speakers with very complex crossovers, can show significant differences with many amplifiers.  That is why the David Clark Amplifier Challenge specifically excluded electrostatic speakers, and not because they often shut down amplifiers...that would merely invalidate a particular trial.]

While to be absolutely careful about it and avoid false positives, matching frequency response, for virtually all solid state amplifiers, into voice coil speakers, is probably not necessary to make it impossible to pass either ABX or prove a consistent preference.  Matching just at 1kHz is sufficient in most cases, and it was often done that way in many ABX demonstrations.  It generally comes close enough for most people, in a double blind test, to find what they thought was an easy difference into a difference very hard to hear at all, so hard one has to be careful instead of wild about making judgements based on fleeting thoughts.

I'm a proponent of the idea that blind AB Preference Testing is better than ABX, and similar statistics can be applied to determine if the preference has been statistically verified, or could be chance.

One of the problems, however, is that many audiophiles will see the raw numbers as some kind of confirmation of their earlier views, despite having virtually no statistical significance.  And the second is (as I found in the very first double blind test I performed in 1983) the subject may argue that their preference changed...in such a way as to make nearly all of their "identifications" consistent.

So ABX is a kind of way of forcing the situation to prevent these kinds of false arguments.  But if you don't fear these false arguments, preference testing is faster and requires only a relaxed judgement, the same as for actual listening.

Most of what people hear sighted is based on "thinking" of some kind.  People have to think of the words to describe what they are hearing.  And this thinking more freely ranges into the negative depending on endless other considerations (technically know as biases) when things are free to be criticized.  Like those complicated amplifers from Connecticut, for people opposed to complexity and what you might call the Eastern outlook, which I recall from my youth as the starched shirts, the greater formality, than I was used to in California.

BTW, a new Threshold has arisen, with new headquarters in Texas, not far from where I live.

This reminds me of how I myself was prone to criticize the tin ears of audio engineers, when I was a college student, just hearing the ways of subjectivist audio.  I picked up my first copy of Stereophile in 1975 and quickly became an avid reader of that and The Absolute Sound.

Anti-establishment, having arisen in the wake of the Vietnam War, touched everything.  It had become the natural outlook on everything.  So of course those engineers were wrong about feedback. No Feedback is better.  You can hear it yourself, when the equipment doesn't blow up when the feedback is removed...

Usually a lot louder too...

Some people, all of my audiophile friends, and all the audiophiles I know socially, are subjectivist in the sense of still having this outlook, that the audio engineering directorate doesn't get it, you have to go offstream to the likes of John Curl (a strong anti-ABX subjectivist who personally knows we still haven't solved the amplifier problem, which might surprise some because his products have been objectively excellent as well, so a perfect example of a good engineer who is also a strong subjectivist) to get your best amplification (most of the amplifiers I own today are Curl amplifiers, which keep working and are never bad sounding, not because Curl has special lock on what makes amplifiers sound good).

But I no longer see it as just the Engineering directorate, it's the more credible group of audiophiles as well, those who have seriously considered the issue, done well designed blind tests on themselves, and/or understand the nature and consequences of perception.  And audio scientists and so on.

I should perhaps disclose also that I myself R an engineer now too, as a member of two engineering societies involved in Audio.

Without double blind (and level matched) testing your findings are worthless, and without statistical verification they are just one useless data point.  Most audio tests are at the worthless level.

Worthless tests are fine, as an amusement.  But it goes wrong, when people come to feel inadequate.  Then it's audio nervosa.

The creed of audiophiles should be much like that of radio amateurs.  An audiophile should try to bring greater pleasure into the lives of other audiophiles.

That's tricky.  I don't think it means, necessarily, that we should lie.  Mostly less verbosity, and occasional avoidance of telling the whole truth, as perceived perhaps, and there's great justification in that.

But I think generally it doesn't involve black vs white comparisons.  It doesn't involve forcing others into one's own agendas, perspectives, or even practices.  It involves listening to others and trying to appreciate things from their perspective, what they are reaching for, and the ingenuity of their solutions so far.

Anyway people learn best when they want to learn, when they are at the point of sincerely wanting to know something enough that they ask.  Before that point, advice is merely poor salesmanship or street fighting.













Saturday, September 2, 2017

Help

A friendly man at the audio meeting kindly offered that I borrow his spare Threshold SA/2.  He said something about my Krell FPB 300 being complicated, and therefore not as musically pure as the Threshold.  Oh, and his SA/2 blew away the Krell integrated at a previous meeting, he said.

Given the many things I've said to other people over the years, I suppose I deserve this.  It starts long ago and far away...

Things have really turned around from the days, way back in 1978, when I was working at an internationally famous (and perhaps not all for the best reasons) audio dealer and tube equipment modification factory called Audio Dimensions (me and several other rogue technicians from diverse elite backgrounds, led by the Tu-Be or not Tu-Be wizard himself, for a few years anyway, "Ike").

Threshold was one of the key brands we carried.  Ike was a serious tube freak who had been experimenting radically on tube gear since the 1950's, and he might have preferred to carry Audio Research, but there was already one Audio Research dealer in San Diego, and since we made what you might loosely consider competing products, often liberally borrowing ideas and circuits and especially parts values from Audio Research gear, this wasn't going to happen.  We actually carried mostly solid state amplifiers, except for in-house, and the direct tube driven Acoustats.

Anyway, Threshold had almost zero respect among the tube freak technical staff at the store, and although Ike and sales staff would be very careful what they said around many customers, the mask would come off when the front door closed.  We carried the so-called Class A models 400A and 4000A, and pretty much believed their fake Class A was worse than plain old Class AB.  A but fuzzy on the grip.  Mucking with the bias was not the sort of thing real linear designers do.  "Trash-hold" was our nickname for Threshold.  I arrived too late to see a model 800, except at a customers home one very memorable day (he had several, and drove 24" woofers along with Bozaks having 6x 12" woofers).  The 800 seemed to get a bit more reverence, for some reason.  It certainly looked cooler.

Whatever merit our collective opinions had, I've come to see them much more dimly through the lens of time, for various reasons.  We had a number of well known brands like GAS, and a few lesser knowns such as Mike Moffat's first company, and lots of good speakers like Acoustat and Beveridge, but what for a significant part of my short tenure was the favorite amp among the staff, and sometimes the owner too, was the rather new Nikko Alpha III, a MOSFET amp, one of the very first.  I think the owner was thrilled by the prospect of solid state devices operating like and allegedly sounding like tubes.  Well sometime about 10 years later I managed to buy a Nikko Alpha III, and I'm not sure it was the wonder we always thought it was.  I always grew tired of listening to it for some reason, I think it had high IM from inadequate driver circuitry, however no measurements I performed in the early 1990's confirmed this (I didn't have decent test equipment until around 2010), so I don't really know, perhaps there was some other problem in my system, I went through fixing many many problems, often years after they had started, finally I decided that no matter what I did the amplifier sounded bad.

But anyways, after quitting my job there, I didn't much follow the history of Threshold products, since they had never interested me in the first place.  One guy who became one of my best friends a couple years later got suckered into buying the Threshold 4000A that was at the bottom of the store rack for many years.  The deal involved him trading in a pair of Marantz Model 9's, and his KLH Nine's, for LS3/5A's in every room major room of the house, 5 or so, and the 4000A, because a 4000A could drive up to 5 pairs of LS3/5A's, no problem, Ike must have said.  Not much later the buyer found it necessary to volume control autoformers for each one, that's where somehow I met him through his installer who started asking me questions about Threshold amps, since I had once worked at the store, then introduced me to the guy with the 4000A, who became one of my best friends for several years, and I miss him now.

When I heard about his deal with Ike, I had the greatest sense of loss.  He had traded in three of the most rare, most well respected and legendary products for a pile of trash just for convenience.  My opinion then and still is that every room needs a high end system.  The Model 9, when it crossed the bench at the back of ADI, had produced the nicest looking square waves of any tube amp that had ever crossed the bench.  I don't recall hearing it though.  I'd wished I had.

I thought better of the LS3/5A's at first, they had been the little darling of the store, until I myself owned a pair, and couldn't stop modifying them into something completely different.

But I never thought much of any Threshold product, except obviously the 4000A could provide a pretty good amount of current, at least enough for a serious 4 ohm load--though the guy mostly kept the other rooms turned down, I think no more than 4 at once making about a 4 ohm load...

Nelson Pass was not the only designer I now greatly admire that I thought was a total charlatan then.  Certainly I'd include Bob Carver, I mean what had he done except create cheap high power amplifiers following a old and bad design (quasi complementary, which I've now come to believe isn't that bad). And he had these bogus non-linear preamp circuits that created greater peaks, less apparent noise.  All that is phoney baloney (and I still pretty much think so).  The best sounding nearly always is to be as linear as possible.  However, frequency response adjustment is a linear thing, and fine when done correctly.

Now, btw, I think I have very much respect for both Pass and Carver, about the same as John Curl--whom I've always respected.  They are all very ingenious circuit designers who have been very successful...no doubt a result of many positive factors.  However, one should avoid hero worship.  Just because people are good at one thing--ingeniously designing high performance audio circuits in this case--does not mean any of them are more than amateur audio scientists.  Engineering is one thing, design another, and science yet another.  Carver may be the most in line with audio science as it exists, though curiously he now makes tube amps (i.e., what he can sell, since transistor fads didn't follow the science very well).  Curl and Pass are both of the sort of "everything matters" school of audio design.  I think that's fine in some ways, I want my amplifiers to be Better than is actually necessary.  But both of them are essentially refuseniks when it comes to doing blind testing, particularly of the "prove you can hear it" variety like ABX.  And, basically, you can't do objective science without blind testing.  You can only prove things, if you to want to consider that proof, to yourself.  Or you can fool suckers, but that's not proof at all.

Carver, on the other hand, promoted a kind of blind testing marketing stunt, very much in line with actual audio science and engineering.  Proving he could make his amplifier sound identical to any other by adjusting the frequency response under load.  That's brilliant marketing with a solidly scientific slant.  However, of course it didn't play well in the increasing tweak funded audio industry, where spending more and more for purportedly necessary extreme technology increasingly became the norm.  Carver was far out of the mainstream audio nut mainstream.  But he had his fans, others who didn't like the combination of BS and high prices in other gear.  Last year I was quite surprised at how nice an old Carver amplifier sounded.

*****

Actually, I had no knowledge whatsoever of the Threshold Stasis models until the early 2000's when I was refreshing my Nakamichi cassette player collection, and learned about the Nakamich variety first.  Long before I even knew there was an SA/2 I knew that Pass had left Threshold and designed a series of MOSFET amplifier for Adcom.  I had thought that had happened in the mid 1980s.  A friend and I had been very interested in trying one of the Adcom amps, as they are rather high bias MOSFET amplifiers, and my friend knew that MOSFETS can be perfectly linear under the highest bias, unlike any other amplifying device.  However he later calculated that as the Adcom amplifier use many MOSFETS, the current in each one doesn't come clost to high enough for complete linearity.

At least a decade ago I had learned about Aleph amplifiers, and lusted for them, and Pass Labs amps, and lusted for them, and First Watt amps, and lusted pretty much only for the F5, which is in my mind the few with a High Fidelity design.

Since the time I bought my Krell FBP in 2008, I have lusted very mightily for a big really Class A Pass Labs XA 160.5 or above.  As much as the Krell is class A in momentary biasing, not so much in thermal stability.  The XA amplifier are, I would admit, even more Class A than my Krell.

But een in the perspective of an XA 160.5 or 200.5 monoblock pair which might replace it, the Krell FPB 300 is an economizing amplifier, which throttles power consumption back to a "mere" 300 watts when not playing anything or very hard.  When I'm actually playing music, the FPB 300 runs at the 2nd plateau which consumes about 600W for both channels, but it can ramp up to 1200W (or higher) for awhile (the fourth plateau).  A pair of Pass Labs XA 200.5 monoblocks constantly consumes 2000W continously when running.  The 160.5's would be 1500W.  That would be a bit much for my 14x16 living room, actually, even with my top of the line Carrier central air system.

Just in the past few months, I saw an SA/2 and was somewhat intrigued.  It's a nice looking amp.  However, I didn't think it was in the current power class I need for Acoustat 1+1's.

Now I've seen the mighty SA/12e and read about the SA/1 and SA/4.  And they sound...interesting.  The SA/12e looks like it might actually deliver something like full rated power in Class A.  OK, that's the Threshold I want (or maybe the SA/1e, which some say is better).  I don't want some friend telling me I deserve less.  Though I see now that the prices of the final top dog Threshold amplifiers is higher than the Krells...high enough really to be out of reach.  I'd sooner get an XA 160.5.

If High End audio is about anything, it's about long term lust, and I can tell you from experience you should never settle for second best, except for pennies on the dollar, and then be prepared to lose a lot more pennies.

In this regards I completely disagree with the likes of Floyd Curl (whose book I'm now reading, if nothing else, he is a very experienced audio engineering scientist who knows a lot of things valuable to me, but he's also too much a promoter of multichannel to be objective about stereo).  He wants to reduce me to a practical Consumer of equipment engineered to Reproduce Music, end of story.

I am not a Consumer!  I am a Player!  And I am a Magician!  And I'm a Kid Who Plays With Big Toys and Lusts for More!

Perhaps that's actually what the science of Audio Equipment Engineering ought to be about.  The Psychology of Lust and Stage Magic (fooling people, especially yourself).

The lesson of life is...you ultimately get those big toys you were thinking about.  Then the question becomes keeping them and using them better than nothing at all.

*****

The Threshold 400A is a 100 watt per channel Class AB amp, with a clever circuit that keeps the transistors on both sides always turned on through a kind of sliding bias.  This does not have the transfer function perfection of true Class A.  I was right in thinking it's not Class A, but it might not be a bad idea, either.  I don't see how it would generate "trash."  Of course we hardly ever did blind testing at Audio Dimensions, if at all only once and it wasn't double blind.  A single blind experiment is a magic show.

But I remember when, long after I was employed in audio, Dan D'Agostino came to an audio show in San Diego.  It was the mid 1980's  Now here was a true Class A amp, the KMA-50.  I didn't like the fan, though, and I told Dan I'd like to see an amp with no fan, 300 watts of Class A power when demanded, and it's ok if it runs a bit hot.  I told him not to slide the bias, that was fake, but hold it for awhile (see earlier post)...

Unlike Pass, D'Agostino was clearly going for the true Class A, and I respected that.  The KMA-50 used so much power it  needed a fan, and yet only produced 50 watts (well, maybe more into lower impedances, I didn't think  much about that then).  So I respected him more than Pass and Carver.  I knew little about the various Levinson Class A amps until much later.  I had also had known about the Electro Research A75 by reading Stereophile about it.

Ever since the Aleph era, it was almost seeming like Pass was on a mission to erase the idea that he ever made "Fake Class A" through sliding bias like the 400A and 4000A.

Anyway, I also started reading about "Papa" at the Rocky Mountain shows, and his workshops, and boy I thought I was missing a lot.  But I did read many of the white papers.  And I've seen Pass a lot at DIYAudio, which I read a lot.

So, like many people I think Nelson Pass is the very definition of cool.  But should I swap in my 19 year old amp for a 34 year old amp that Pass designed, just because Pass designed it more simple to make it sound more pure?  After I complained the 100W rated SA/2 might not have enough power or current capacity for my incredibly inefficient Acoustat speakers, the audiophile bragged that Nelson Pass always delivered high current.

Well, I didn't want to argue, but I well knew that NOT to be the case.  Nelson Pass has been anything but consistent over the years in his designs.  He loves to play around and try different things, not just high current amplifiers. Curiously, the XA 160 was a surprising weakling in Stereophile tests in 2003.  John Atkinson wrote:

The Pass Labs' measured performance left me scratching my head.  Its massive construction, high heat output, and high price suggest a limitless delivery of watts--yet assuming neither review sample was malfunctioning, the XA160 offers only moderate power.  Its current limiting of the clipping points is also something that historically has been regarded as a bad thing in a solid state power amplifier.  But like its highish otput impedance, this is something that is more typical of tube designs, which might well go some way to explaining why MF felt the XA160 to sound like a tube amplifier.
There is now a comment in the online version that this issue represented a production error of some kind, but a retest was never done on that exact model.

A few years later, Nelson Pass remarked:
Some manufacturers recommend the arc-welding capacity of their amplifiers -- we specialize in sounding as good as possible into reasonably ordinary speakers.  This is of course an arbitary decision on our part, but we are content with it.  There are more powerful amplifiers on the market, and we are happy to see them get their share of business as well.
The limited current issue was addressed and fixed starting with the .5 series of Pass Labs amplifiers.  That's precisely why my major lust for Pass Labs amplifiers  begins with the .5 series, such as the XA160.5, rather than their predecessors.   Not that a .8 isn't better, but the good high current starts with the .5 models.  And if Acoustat capable high current is the thing needed, you can just write off all the Aleph series amplifiers, all the First Watt amplifiers, and so on.  As I said, Nelson Pass likes to play around with different things, not just Curl or Krell high current.  However, I'd love to have a First Watt F5 powering my super tweeters, and I intend to build one someday.

Anyway, a few weeks later, this guy sent me a link to an add for Stasis 2.  He said that was a 200 watt amplifier which might meet my needs better.

I did a little searching on that model, and found someone in 2012 who complained of having bought one of those and spending a ton of money refurbing it, and they could have had a Pass Labs amplifier instead.

Well, that would have come to my mind also...

But anyway, what about the SA/2?

As it turns out, someone online has already done a related comparison, the flagship Krell (from 1998) vs the flagship Threshold of a few years earlier, the Threshold SA12/e.  The Krell is characterized as being "a little better" than the Threshold overall, with the difference being greater transparency, better extremes, and rock solid bass.

My FPB 300 is the smaller version of the FPB 600 preferred by that author, made at the same time, and has the same circuits just scaled up in the number of transistors and transformers.  The SA12/e is the ultimate Threshold, the biggest and most powerful Class A monoblock ever built by Threshold.

Which Threshold amplifier are their best?  Reading this thread, it appears the most respected Threshold amps ever made are: The SA/1 monoblocks with e mod in balanced mode, the SA/4e stereo amp in balanced mode, and the SA/12E in balanced mode.  BTW, over at DIYAudio.com, when Nelson Pass is asked about these amplifiers, he says it has been 25 years since he even listened to these amplifiers, and his sense of what sounds good in amplifiers has changed since then, but he remembered the SA/12E as being an improvement over the SA/1.  He also said that they sound "similar."

The Threshold amplifiers are all bipolar.  For some reason, since he left Threshold, Nelson Pass has sold mostly MOSFET amplifiers.  If amplifiers sound different, we might expect them to be a little different.  Or maybe it's just those "simple" circuits...

*****

Anyway, despite age, factory claims, or what any particular reviewers thought at any particular time (and of course, just like collectors, sellers, and fanboys, reviewers can have conflicts of interest) or even what their designer thinks of their earlier work now, it's particular amp could sound better than another, right?  Maybe there's some special magic in some particular model, you just gotta hear it, if you don't hear it for yourself, you are missing out.

Maybe not.  There's been a long line of audio engineers and reviewers that the amplification problem has been solved, to the point that "all high fidelity amplifiers sound the same."

Julian Hirsch, the longtime equipment reviewer for Stereo Review, declared that all good amplifiers sound the same in 1975.  But given his previous history of occasional hyperbolic claims, nobody should necessarily have taken that seriously.

But by the late 1970's, the ranks of people making this essential claim had grown quite large, and to include a number of pretty respectible audio engineers and reviewers.  And by the early 1980's there was an extensive body of double blind testing done by audio amateurs, engineers, and provacateurs, all essentially showing the inaudibility of amplifier differences, and more solidly the non-existence of unknown factors which could make amplifiers sound different.  All this happened, but was pretty much kept out of view of most consuming audiophiles by the growing High End audio magazines, which promoted the opposite ideas, that every amplifier has a peculiar sound, and if you don't get the right one, your life is ruined (and that right one will most certainly change in the next issue).

And in the late 1980's, this turned around into being more about digital, digititis and so on.  But I've got enough things to talk about in this essay.

In fact this amplifiers-sound-the-same stuff grew out of the original "objective" (though not called that until decades later) way of looking at audio design.  When electronic audio reproduction began, it barely worked.  But by the late 1940's, low distortion and high power amplifiers had been created through novel circuits and the use of the new-at-the-time negative feedback.  Getting the harmonic distortion below the approximate perceptual level of 1% was a huge achievement.  It's becomes easy to hear the effect of harmonic distortion pretty above 3%, and the intermodulation distortion that is caused by the same thing (nonlinearity) is quite objectionable sounding.  But by the 1940's, amplifiers could be made which were not only not objectionable sounding, they were starting to have no effect on sound at all.  By the beginning of the 1970's, it had become possible to push distortion even lower than that, ultimately to level like 0.03% which there wasn't any good evidence anyone could hear.  These numbers had a profound effect on the thinking of Julian Hirsch, who had seen a trajectory of great improvement, with what had originally seemed impossible now commonplace.

But meanwhile, the "subjectivist" reviewer like J Gordon Holt and Harry Pearson arrived on the scene, essentially claiming the numbers don't matter, listen for yourself, and their finding was that  many of the new super low distortion amplifier did not sound as well as the best of the previous generation of tube amplifiers, and also the new generation of tube amplifiers that was appearing from companies such as Audio Research.

A rift was created, grew over time, and now dominates audio.  Subjectivist reviewing is now the majoritarian way it is done.

There are many many stories behind all this.  Stories told differently depending on who is telling them.   A friend of mine was involved in the Stereophile amplifier test of 1979, in which blind testing did find at least two top shelf amplifiers whose difference could be heard under double blind conditions.  As it turns out, one was tube and the other solid state, the the resulting effect of differences in output impedance is now well understood by all audio objectivists.  At the time, many subjectivists, as I was at the time, glorified in the new findings, which disputed the findings of a Stereo Review test a year earlier.  But while some were temporarily shocked, it didn't last long.

One of the bigger things talked about is how ordinary audio engineers were wrong and had "missed" TIM, which was caught by some of the brighter lights, such as Matti Otalla, who made some very impressive low TIM amplifier for the Citation line of Karman Hardon.

Many many have peddled this story, but it has been overtaken by a similar but related story of how "feedback was used to cover up all ills" but "that doesn't work," TIM being part of the technical footnoes.

This has become a major mantra in subjectivist audio.  But as applied to well engineered audio equipment, it is entirely wrong.

For one thing, it was proven by audio scientists not long later after the discovery of TIM by a few engineers, that TIM is just the same old IM, but cause by a newer kind of sloppy engineering made more likely by transistors.  The same underlying phenomenon could just as well be measured by better IM tests.  The old IM tests were created for tube equipment which had lower bandwidth and wasn't so subject to front end overload.  Transistor amplifiers needed a tougher test for high frequency IM.  And so, the 19+20 kHz two tone IM was invented and is pretty much the standard now (though, ironically some say the old IM test should be used also).  And that was the end of the chapter on TIM in the objective audio community.  An actual test for TIM has never been standardized, because it isn't felt to be necessary.  This was not a failure, but a victory for objective audio science and design.

As far as feedback being the bane of all good design, that is either such a nebulous argument it cannot possibly be debunked, or just obviously wrong, as nearly all of the most widely loved amplifiers of the last 70 years have used feedback, and many have used it not entirely correctly either (but still gotten away with using it wrongly).

It is obvious feedback can be used wrongly, but audio engineering has guidelines and techniques, which if followed, result in the correct use of feedback.  It's not cutting edge science.  In the 1950's Peter Baxandal worked out the optimal amounts of feedback in certain simple cases using mathematics.  The conclusions are still a bit radical, and not always followed.  The upshot is that either very little feedback should be used, or very much.  It's the in-between area that can result in increasing amounts of distortion.

Many famously good amplifiers have gone after the large feedback side.  Large feedback amplifiers have included the Halcro and Wolcott, both highly praised by subjectivist reviewers.  And one of my favorites, the Electro Research Eagle 2, loved by J Gordon Holt.

I'm not saying feedback can be used wrong--of course it can!  However, it's not clear which "early transistor amplifiers using too much feedback and therefore having TIM" are the ones that are actually supposed to sound horrible.  Whom did they sound horrible to?  Was double blind testing done???

One early transistor amplifier using lots of feedback, the Sony 3200F, was the long standing favorite of my super audio nut brother in law.  Since tweako audio was both his business and his passion, he went to all the audio dealers, all the shows, everyone's house who would let him in to hear his tweeks, and sometimes his amplifier, a 3200F.  He told endless stories about how people preferred his 3200F to many of the most highly touted amplifiers.  It remained his favorite until 2014, when he switched to a particular Emotiva amplifier.  I believe Emotiva is a great brand of reasonably priced no bullshit high performance audio products--nobody really needs something better than an Emotiva--so I'd agree with him on that, but there's no reason to believe Emotiva or one particular Emotiva is unique.  Anyway, wrt the Sony 3200F,  I don't doubt it was a high fidelity amplifier either, at least as designed and when brand new...it might be a bit worn out in 2014.  It got a rave review in Audio in 1968, and had perfect objective performance up and down the line.  In 1968.  Are all these "bad sounding" high feedback amplifiers all made before 1968???

One amplifier, however, which seemed to slip off the tongue a lot among subjectivists in the 1970's (I know, I was there) was the Crown DC 300A.  Now this amplifier was widely held by subjectivists to be a bad sounding amp because of feedback.  But honestly I've never heard it myself, and I know that many many people praised it as a good sounding amplifier.  It was in the Crown lineup for a long time, and Crown was a very successful professional audio gear manufacturer.  I suspect it may not be a bad sounding amplifier at all, it was just a convenient target of something most consumer audiophiles have never heard.

Another amplifier supposedly in the "measures well, sounds bad" category is the Audionics PZ-3.  The PZ-3 was so-named because it had 0.03% distortion, a long held goal of what would be inarguably "good enough."  Notably according to Lynn Olsen, a very experienced audio designer and blogger, the PZ-3 was bad sounding, and his friend designed a low TIM replacement, the CC-3, which became a famous and top seller.

The PZ-3 however had an objective problem.  The undersized driver transistors would blow out.  The PZ-3 cost Audionics a lot of money in warranty repairs.  And the low TIM (which was a big buzzword at the time) CC-3 was a hot seller, which having the buzzword of the hour saved the company.

But it seems not everyone thinks the PZ-3 was actually a terrible sounding amplifier.  Perhaps it sounded better on some speakers than others because of impedances.  I was thinking of this when I saw a PZ-3 for sale on eBay, said to be in excellent working condition.  There was no CC-3 for sale.  Sadly I missed my chance to buy a PZ-3 and find out for myself.  And see if I could confirm it blind.

Though I have a good candidate for sounds-bad testing of both measurement and blind listening kinds: the Nikko Alpha III.

Once again, I don't see any evidence that blind tests were performed to prove the PZ-3 was even an inferior sounding amplifier.  And even if it did sound different, it could have been because of high IM, or it could have been because of it's dynamic output impedance.  It's not due to some factor which audio engineers have never understood or invented a measurement for, that's for sure.


By the mid 1980's I began hearing about double blind testing all over again.  I decided to try this myself.  I was sure I had the sound of capacitors nailed, having read Richard Marsh's seminal article on capacitor types, and even hearing a lot about it previously.  I constructed a box in which I could select from a worst-case case electrolytic capacitor (actually, 5 in series into high impedance), and a best case film capacitor.  The box was designed with an inner switch which could be set by my sister after doing a coin toss.

It became immediately apparent to me I could not tell the difference between these two kinds of capacitors.  Everything I listened to and for sounded the same as I turned the outer switch.

This started to change my thinking a little bit, but not my actions very much.  By that time my main audio system used two different tube amplifiers and a big bipolar amp for triamplification.  But my primary tube amplifier, a Citation II, was giving me endless trouble and I wanted to change.  I almost bought an Electro Research Eagle 2.

Now many years later I know the 1980's were rife with objectivist challenges.  For many many years David Clarke had an "amplifier challenge" in which he bet significant money that under properly controlled blind tests, people could not hear a difference between amplifiers...amplifier of their own choosing.   Mr Clarke traveled widely doing tests blind test shows for many audiences.  Nobody won the bet.

Part of the challenge involved matching levels very carefully, to 0.1dB or better.  If the amplifiers varied more than a few tenths of a degree in frequency response, recognized to be audible by audio objectivists, he would equalize one of the amplifiers.  To satisfy listeners, he would equalize the "lesser" amp to sound like the better one.

This kind of level matching is virtually never done by non-objectivist audiophiles when doing equipment comparisons.

Not too differently, Bob Carver challenged magazine reviewers, notably at Stereophile, that he could make his newest transistor design sound indistinguishable from their favorite tube amplifiers.  It appears that nobody ever proved Bob Carver wrong.

One of the key issues is not just matching the "frequency response" specification, as it is measured into an 8 ohm resistor, but the actual frequency response of the amplifier under the load of the intended loudspeaker.  These are very different phenomena.  Loudspeaker loads are very complex, and when an amplifier has a sizeable output impedance, as most tube amplifiers do, the amplifier response will be significantly if not greatly altered by it.

I myself had observed this in 1974, when I replaced my Dynaco SCA35 amplifier with a Marantz 2270.  At first I was greatly distressed by the loss in low frequency response.  After a month or so, however, I decided this was the new normal.  The SCA35, I decided, had bloated bass, and the 2270 had tight bass.  Their actual frequency response specifications would not have led you to think they could have an audible difference.  But they had very different damping factor, and that was very important with the low efficiency Advent speakers I was using.

Now in this case, I heard the difference, and decided new is better, perhaps not unlike a lot of people switching to transistorized amplifiers.  Meanwhile, a very very small number continued to think tube amplifier were better.  Most people were entirely unaware of this tube backlash, even into the 1990's, even now.  I caught the backlash side as soon as 1978, when I worked at a tube amp chop shop.

Even now there are long discussions between well known audio subjectivists and objectivists at DIYAudio, and perhaps a few other places, though never in any Audio Club in which I've been a member.  Most audio clubs, with the exception of the famous Boston Audio Society, and a similar Michigan group, are on the audio subjectivist side.  This may have something to do with sponsorship by major high end retailers, or it may be leanings of those who are interested in such societies.

What do I think about all this?  Though it's hard, hard to write down the full argument (I've already tried and failed many times in this blog), I think the audio objectivists are essentially correct.

I'm think I'm pretty much believe what NwAvGy says in this long and thoroughly documented article with many links.  And likewise with a large number of others: Ethan Winer--who has written Audio Expert, a book I just bought, the posters at Hydrogen Audio (a website which does not even permit subjective evaluations without statistically valid blind tests to confirm them), Peter Aczel (though his good vs evil rhetoric bothers me sometimes)--I've read a majority of the Audio Critic magazines and his posts over the years, and so on.  Here's an online issue of The Audio Critic which starts right out with letters, the first being a telling of how the late audio salesman and internet personality Steve Zipser was unable to determine which amplifier was a cheap yahama receiver and which was his personal $15,000 super amp in two separate sessions of invited blind testing.  That's very typical in the annals of blind tests, when subjectivists would even dare do them.  Then the magazine procedes to a small discussion of audiophile myths, which is greatly expanded in a later issue.  Then Peter Aczel's famous/infamous identification of the good guys ("white hats") and bad guys ("black hats") in audio.  That white hat/black hat thing is where Aczel crosses the line a bit, in my view.  Not just the identifications, I'm OK with that, but the ugly things he says about people like John Atkinson are OT.  He's a cranky old crank, though basically he's right, I think.  (I touched words with him a few years back myself.  He's the kind of person who, much like his antithesis James Bongiorno, is impossible for me to agree with.  He'll find fault with everything I say, even as I'm trying my best to agree.)

I know matters may not be quite as simple as a particular article or even book is able to present.  My favorite audio website, DIYAudio, has a wide array of both audio objectivists and subjectivists.  John Curl and Nelson Pass are among the most celebrated of the subjectivists who believe there is still a large "unknown" in what makes amplifiers sound different.  Scott Wurcer and moderator SY are among the more celebrated objectivists.  It's impossible for me to capture even the spirit of the arguments in this small post.  The major forum for objectivists and subjectivists to argue with each other is the nearly endless Blowtorch blog, nominally about the thinking behind John Curl's Blowtorch preamp of many years back.  This rambling discussion has gone on for more than a decade now and represent about ten thousand pages just in "Part 2."  I've read hundreds of pages myself.

There have also been smaller discussions specifically on what does or does not cause amplifiers to sound different.  But these small discussions may be dominated by one faction or another, and for whatever reason I find reading The Blowtorch Blog Part 2 linked above to be the most interesting.

It is of course false that "all" amplifiers sound the same.  But that's not really the question.  The question is whether we know what makes amplifiers sound different.  And the answer to that is a simple yes.  And High Fidelity amplifiers, which we know how to make, are indistinguishable, and lesser amplifier can most often be equalized (or the higher fidelity amplifier equalized) to sound identical.  No one has ever proven otherwise.

An amplifier, and the signal sent through it, are in principle fairly simple things.

High fidelity amplifiers, defined in a kind of circular way, are indistinguishable from each other now.  However, when I say "high fidelity" this does not necessarily include all amplifiers.  In fact, it may include rather few amplifiers is the use of compensatory equalization is not permitted.  Many many amplifiers of today, and especially including many tube and other high end amplifiers, could sound different because of different frequency response under load.  So, if we just discard everything that doesn't meet the high fidelity standard of roughly +/- 0.1dB from 20 Hz to 20 kHz, we aren't left with very many amplifiers actually.

The Krell FPB 300 however is pretty much in the high fidelity group.  And I suspect the SA/2 is also. This probably wouldn't be true of an Aleph amplifier, or some of the First Watt designs.

If legions of people haven't been able to prove they can hear differences not qualified by high fidelity standards, I don't think I'm going to be able to either, nor anybody I know.  In fact I've run 3 blind tests on my most serious audiophile friend over 3 decades.  It didn't seem to change his thinking after he lost every one.

In the end, it's not really about particular amplifiers.  It's about audio engineering.  It's whether or not scientists have a handle on what audio equipment needs to do, as audio equipment.  Basically the audio science says you need primarily the flat (or identical) frequency response (under load of course), and after that, fairly low Intermodulation Distortion (IM).  Harmonic distortion as such is not detected very well, you may need over a percent or so to hear it on real music...but IM is far more noticeable and objectionable, and should be below 0.1% if not 0.01%.  Beyond that, there is no X factor, unknown to engineering and science, that "explains" why equipment sounds different.  In effect, you don't actually need to "listen for yourself."  That's what the snake oil salesman always says in the hopes that some will have their expectation bias follow his suggestion.

Peter Aczel has been one of the most forceful critics of audiphile subjectivism, and he discusses the X factor idea.  That's really what it comes down to, and in 37 years since 1980, no X factor has ever been discovered.  There have been books written, such as by Ethan Winer (I just got that one) debunking audiophile subjectivist myths.  There are major websites, such as HydrogenAudio, dedicated to the objectivist view, to the extent that purely subjective claims cannot be made without methodologically valid blind testing.

*****

So, knowing all this, what does one do?  Does one buy the cheapest possible amplifier?  Well if that's all you can afford.  But many preaching the objectivist audio creed buy very nice amplifiers.  Boulders even.  Because it's nice to have something much Better than actually needed.  If you can afford it you can flaunt it.

What they don't buy, are non-high-fidelity amplifiers, such as most SET's, which have predictably audible distortion and impedance interactions.

After my last tweako amplifier...actually the Nikko Alpha III I finally got in 1989, I moved on to what I thought plain vanilla objectivist amplifiers, the Parasound HCA's, only later discovering Peter Aczel was no particular fan.  But I don't think he was opposed to them completely, despite complaining about construction quality not being the spec he was used to (he liked megabuck Boulder amps).  They measure well enough to be fully High Fidelity, as well as having the extra High Current capability that has been Curl's trademark.  No slewing amps here!

But I didn't really think the HCA-1000A was good for the 200W recommended Acoustat 1+1's, and indeed when I first got them, and running full range, and equalizing the bass response heavily, and playing loudly, I got the HCA-1000A to shut down.

So, I began to think about amplifiers, and this is always the way to start...speaker first, and then what kind of amplifier does the speaker need.

If I had even known about the Threshold SA/1 and SA/12e and SA/4 they might have been on my list.

I knew about Pass Labs (too expensive), Aragon 8008 BB (about the most massive power supply ever, 2kW of torodial transformers), a few others, and Krell, all noted for high current.  Parasound just sounded too pedestrian, the JC series had not come out yet, the 2200's had a mixed history and looked a bit junky.

I really figured I'd get the Aragon but I kept losing bids on them.  Finally there was a reasonably priced FPB 300.  Oops!

The FPB 300 was like a dream come true.  If I hadn't actually told D'Agostino that I'd like an amp like that in 1985, it was the kind of thing I had long been thinking of, since having finally turned away from tube amps which had always been too high maintenance, and which I didn't really think necessary.

It had everything I wanted, not just the high current and power made possible by 3kW transformer, huge number of transistors and all.  It has the full regulated power to the output stage, another longstanding dream, a big one.  It has the real full balanced operation.  It has high power bandwidth: 300kHz.  I used to think it had a no feedback output stage, which I figured would be most perfect for electrostats.  In reality, there is no global feedback, but the drivers and outputs are locked together with feedback.  That's actually still fine and good, and reacts to speaker push-back as well as anything.  I'd bet it has relatively low settling time with regards to pushback from the speaker, which is the biggest factor in electrostats (they reflect most power back to the amplifier).

The Strickland designed amplifiers do something similar because the output side of the outputs has no feedback, feedback is taken from the input to the outputs.

It has always sounded great to me.  When I first needed to get it repaired in 2010, I needed a repacement and sure enough the Aragon 8008 BB was for sale again and I snapped it up.  It has been a lust worthy and capable amp, but not as good (in my long sighted usage experiences) as the Krell.

Now there's a long line of people who say the Krell sounds "slow" somehow, or "dark" or whatever.  There's no reason to believe this whatsoever.  None of these people have probably done blind testing, blind testing is extremely rare and especially among subjectivist audiophiles.  They're driven by their expectations, notions like "complexity" or "industry", perhaps the dark colored aluminum itself.  And perhaps their love of things that glow in a particular way.

The Krell has wide bandwidth--to 300kHz or beyond--more than most amplifier Nelson Pass has ever designed.  It has a no loop feedback design, limiting the speaker pushback to very fast settling output stage.  It has regulated power, class A operation, low distortion (spec is 0.03% !) and noise.  This is a high fidelity amplifier, and got rave reviews by leading subjectivist reviewers when it came out, as the #1 worlds best at the time.

If in double blind comparison the Krell actually was found to sound "darker" than some other amplifier, it would be most likely because the other amplifier was editorializing, adding brightness, probably IM, that would grow tiring over time.

Otherwise, there would be some aspect of it's behavior, probably easily measurable, which would expose this characteristic.  I know of nothing of the kind.  It is somewhat complicated, yes, but the resulting IM distortion is conservatively below 0.03% even by the most stringent tests.  And it is the IM, not the simplicity or complexity, that is the important factor.

Just because lots and lots and lots of people believe something, doesn't make it true.  Lots of poor evidence doesn't make it much better.  What's needed is at least a small amount of very good evidence, such as the kind that comes from careful measurements or double blind tests.

Anything else, is pretty much a waste of time.  It creates false "findings" which are really superstitions, that can be long lasting and very harmful.

When it comes to power amplifiers, high fidelity power amplifiers that is, the problem of amplification is so well understood, and so well handled, that pretty much you do not have to listen if you have trustworthy objective information.  You do not have to "listen for yourself" and in fact, unless done with all the controls, is an ivitation for trickery.

Peter Aczel said you do not have to listen to Power Amplifiers, in 1990.

Now speakers are a different kettle of fish.  There is no such analysis or perfection of loudspeakers.

Also, there's such a thing as Infidelity: Non High Fidelity amplifiers.  Non-High Fidelity amplifiers have high levels of distortion, limited or unflat frequency response, or high output impedance.  These are cases of not being faithful to the source.

But with some speakers, in some room, some people might like the effects.  Of particular use, and not necessarily bad, is high output impedance.  It's not actually fully settled science how the speaker and the amplifier ideally should interact.  It's quite possible a higher impedance is better under some circumstances.

And so, a pioneer in transistor amplifiers, Bob Carver has gone to making tube amplifiers.  And there is some argument for it.

But if it's a different frequency response that's created, and that's likely the only good that could come out of a high output impedance at the speaker interface, that effect can equally well and more efficiently created with digital equalization.  No noise nor distortion need be added if both inputs and outputs to the EQ process are digital.

I'm there.  Famous reviewer at The Absolute Sound and longtime friend of Harry Pearson, Robert E Green, has long been there.

Nowadays, given digital sources, it's trivial to stick in any kind of digital equalization you want.  My preferred vehicle is the very interactive Behringer DEQ 2496.

Tweako audiophiles would prefer to do their adjustments through largely ineffective and very costly tweaks, more largely for tweaking the imagination.


*****

But the Krell is still perhaps not a very good objective choice, largely because it is more than I need.  There's no real reason I "need" Class A operation.  It's a waste of energy, it leads to a need for more maintenance than other amplifiers.  I personally like the ideas in it though.  Perhaps I'll discover a reason why it is, actually, needed.

That's my penultimate argument with audio objectivists.  We know a lot about the requirements of audio equipment (especially amplifiers and digital) but there, indeed, may be more.  I think one of the bigger open ended things is frequency response.  My personal belief is that we need 40kHz response, as well as deep infrasonic response.  So I continue to work on these things.  I can't prove the need for them, but I think there's some possibility they may sometimes have an effect.

This argument does get off the track in my own peculiar way, with my own theory of information, and so on.  None of the things I want conflict with ordinary High Fidelity requirements however.  I just go beyond it in a slightly different way than wanting more of the good stuff (linearity) than necessary.

My position breaks from the objective ones precisely at the point that audio is engineering in pursuit of reliably conveying musical information from the musical producer to the consumer.

My idea of the goal is not reliable conveyance, but peak experience.  Audio should be capable of delivering, on occasion, peak experiences.  Audio science shows what reliably transmits the information, but where is the science of magic magic?  I think, partly, it's in the improbabilities.  We can predict to a great deal of certainty what amplifiers are going to sound different in a fair DBT.  But it is never perfect certainty.  There could always be some peak difference that isn't yet accounted for.  We shouldn't fool ourselves into believing these things are going to be ordinarily or easily hard.  They are in fact going to be nearly impossible to hear on a reliable basis.

Peak experiences are not something you can blind test for.  Peak experiences cannot be predicted.  They result from unpredictability more than predictability.

So it is, that people might like the always different (not "high fidelity") vinyl reproduction.  Because of audible noise, listening to a record twice never presents exactly the same information.  Perhaps this is a virtue.

Anyway, this possibility that you are on to something that others have missed...this is part of the thrill.  It can't, and probably you won't even allow it to be confirmed or disconfirmed, because that would likely destroy the suspended disbelief.

The findings of objective audio science should be regarded more as liberation than enslavement to a particular technology.  There is no great need to go to zero feedback, or costly capacitors, or whatever the current fad is.  You can slip past all the fads and carnival barkers, and just do your own thing.  For me, that's electrostatic speakers, and high bias high current power amps.  For you?

Meanwhile, you don't have to bother with testing amplifiers, cables, or whatever.  Or, you can choose whatever cable you like, probably having no deleterious consequences (cheaper cables) except to your finances.  It's usually the more expensive cables that have actual audible differences from not actually being "high fidelity."

It's that freedom I treasure, and the freedom to make things as complicated as they need to be to do the things I want, and not be limited by the superstitions of others.

But as much as you can follow your own path within the fairly wide corridors of high fidelity, and still not be screwing things up, or otherwise, the last thing to believe is that you, just you, or your bud, have really found the answer that somehow decades of audio scientists and engineers have overlooked.  The last thing to do is take over every gathering with your own soapbox.  It's fun to believe you are on to something, but don't make it a crusade, which will only prove to others how wrong you are.  It may be true, but only with the lowest imaginable probability.  Getting others to accept a new truth now is only making a sale.  It is always better to let the come out on it's own, rather than pull it out in a magic show.  Unless you are selling something.

So the last thing I want is patronizing advice, unsolicited help, arbitrary or sacrificial rule enforcement ("all audiophiles must use audiophile cables", "you must listen for yourself"), killjoys ("you must spend more on music than gear"), or anyone trying to sell me something I didn't ask for (I can smell a sales pitch a mile off).

Not that I don't deserve it, a lot of it, at least most of it.

*****

My audio nut brother in law has often said that you don't admit to being an audiophile without being open to criticism.  That's the name of the game.  If you present something to listen to, be it an album, or an audio system, or even make a statement about audio reproduction, you should be open to and expect criticism.  It seems to me over the years of being in audio societies going back to 1978, people are less prone to criticize now.  Even my brother in law rarely criticizes individual audio nut friend systems anymore, if he visits them at all.

Actually, in the audio parties I've had, I haven't gotten very much criticism (except from those you might expect it from) and I might wish I had gotten more (from the people who were silent).

This is clearly a dicey area.  But I'd note that there does seem to be the situation that the people who talk are the ones least interesting to listen to sometimes.  Especially when they're selling something, have a need to prove something, etc.

Criticism is more appreciated than advice, but the latter is more commonly given, it seems.

One thing that is actually a bad thing, is audiophillia nervosa.  When people can't listen, because they think, without good reason usually, that it isn't sounding good.

Or if they feel the need to spend more than they should, constantly, etc.

Regular audio is a need but high end audio is a luxury, a rich mostly-men's game of some kind.  Probably a social substitute for unfufilled sexual needs.  It should not be the kind of additiction that leads one down the tubes.  It's excusable as a kind of bling.

And since it is really just bling anyway, it might as well be blingful, in the ways that resonate with my personality.

Anyway if criticism were to lead to audiophilia nervosa (I'm not sure it does, but "advice" might) that would be a bad thing.

Most of these superstion things, the "need" for special cables and amplifiers, and all the tweaks, etc., do not lead to bad sound.  And they should not be sold as such.  If sold at all, it should not be as a cure to an ill, but to elevate beyond.

And so one should always respect one's peers, or attempt to sound that way.  They are using their NOS dacs, their underpowered SET amplifiers, whatever, that's they're way, it's not like they need conversion therapy (which doesn't work anyway, as I understand it).

Leadership should generally be by example, demonstration of new and better, rather than cutting anyone down.  Or any thing except as part of the argument at hand.

Some people have the sense of coolness which is a lack of uncoolness.  That can be very tricky.  When cooties are found here, they are found over there as well, there's no end to cooties.  You call my Krell complicated...I'll show your Pass Labs is plenty complicated also.

My own sense, I feel fortunate in believing, is more in the sense of coolness being cool things, of which there might be a few duds, but still enough cool to win the day.

I think that's the way Nelson Pass himself feels about things.  He's just playing around, he invites others to join in his game, but he's not telling anyone else they're out of line.

He's praised simplicity, and he's pointed out that simple circuits generate relatively lower order harmonics, which are less audibly offensive.  The higher order harmonics can be horribly offensive.

However, a well designed amplifier with correctly applied feedback (he uses feedback too, and does measurements), even if it is complex, with reduce higher harmonics to past the point of audibility, to below the noise floor.

The "simple" amplifiers many people love, SET's, often generate distortion harmonics up to 3% and trailing downward through all the harmonics you can count just by slightly lower amounts.  Isn't it more a factor that there is *so much* distortion?  Yes, provably the distortion in a high distortion amplifier is audible in blind testing.  Does having higher proportions of the even harmonics somehow make the other better?  Actually, the asymmetric non-linearities behind even order distortions are disproportionately capable of generating IM, which is the worst of all.  The only good distortion is no distortion.

There is no credible evidence vanishingly small amounts of high order distortion produced by more complex circuits is audible.  Pretty much when you get THD below 0.03%, measured under all conditions of interest, there is no audible "distortion," regardless of the order of the distortion or the complexity of the amplifier.

Nelson Pass does not do blind testing, nor John Curl, nor their followers.

They purport to hear the result of complexity, but it does not seem possible that they actually do, in well designed but complicated competing amplifiers like the Krell.  And you will find plenty of complexity in Threshold and Pass Labs amps too.  It's Nelson's best efforts, the SA/1 and the XA's are very fine amplifiers, and I'd love to have one appropriate to my needs.  But there is no reason to believe they are unique in regards to their actual performance.  Other companies are able to obtain lower orders of measured distortion, etc., without resorting to Class A operation or any other of Nelson's clever circuit designs.  There is no objective evidence, either from measured performance or statistically valid blind testing, that they are actually better amplifiers in any way, than other High Fidelity amplifiers of the same power.

And there is certainly no proof.  I don't find either the white papers suggested by Curl or Pass to be fully convincing.  Interesting yes.  Convincing, no.  Clever circuits do not enable insufficient use of feedback to achieve "better" performance.  Correct design of all aspects, both the amplifying and the feedback, is required.  And once you get to a certain goodness, it's quite like more good doesn't help much if at all.  Numbers matter, and the lower the better.  What's only possible is the selective reporting of information, for example rising distortion at high frequencies that intermodulates to lower ones.  It's always possible for specs to be misleading and incomplete.  They are always incomplete.  Measurement can be incomplete, but in the area of amplification all aspects of performance are tractable, and pretty well understood.

So I will not bother with these "simplicity" superstitions.  I've already created too many superstitions and money pits of my own.  I should have spending more time in measuring and adjusting speaker equalization and the like.  I might have been fine with a less costly to maintain amplifier, such as one from ATI or Bryston.

Not to mention, finding better ways to get the music I want playing.

*****

WRT the purported amplifier test, it was as invalid as any sloppy test could be.

Not only was there not serious attempt to match levels, during the interregnum of changing amps I had noticed the preamp balance was off, so I fixed it.  I did not know a vote was going to be taken.

It was a fully sighted, in group test, not level matched, inevitably steered by starting positives from the fans.  And certainly the 2A as a separate heatsink adorned amplifier looked more solid than the highly ventilated and curvey Krell integrated--a very different aesthetic.

I take these sorts of things as jokes.  I voted because I fixed the level.  I'm sorry if it played out that it was a club members amplifier (I had thought it to be the stores), if he felt badly about his amplifier, as a result.

I'd rather not take a very forceful position with other people.  I try to accept them, as far as I can.  I will answer such questions, generally, as to whether A or B is a better sounding amplifier, despite not having any good basis of comparison directly.  I could always add "but it was just because I never hear anything the same twice, or I'm biased toward this kind of thing in a sighted test", etc., but I don't.  Why should I bother, except to be a snob?  A sloppy test deserves no better than a sloppy answer.  Nobody should be fooled.

So in the subjectivist Rome, I just follow along as the other Romans do.  No one should require me to do otherwise.  Nobody should require me to be the asshole who always says no.  If they want to be it, If they want to stand up for real science or whatever, I'm fine with that too, to a point.

But, the thing I think at least now I try not to do, necessarily, is sell my tonic.  I might make a comment that my way is better, but not that you, especially you, need it now.

I find myself increasingly put off by people who are consistently trying to sell some idea.

Though perhaps it's still more interesting than when nobody says anything.