Monday, November 13, 2017

Amirm is back!

I was saddened to see that Amirm was bounced out of two other websites I have enjoyed.  He, and his purely objectivist interlocutor Ethan Winer, were two of the most interesting people at WhatsBestForum, for example, and now they've both been bounced.

I wouldn't say I would agree with him always, or even a lot, but he's interesting to read and one of the better ones at combining subjectivism with some kind of objectivism.  About as entertaining and probably at least as accurate as J Peter Montcrief--who doesn't seem to have written anything in a long time.

Well, now he has founded a new audio website himself, and it looks good enough to be added to my sidebar (actually, some of those you might think would have been taken off long ago, but whatever, I like to tease, just like these guys do).



Looks like it's filled with refugees from WBF and the like.

Tuesday, November 7, 2017

Another Amplifier ???

I saw a very nice looking Hafler 9300 just listed on eBay for $395.  I took a look at this review

http://www.hifi-classic.net/review/hafler-9300-120.html

They measured distortion of 0.0025% at 1 watt, the most important watt, where it was continuing to decrease.  And bandwidth over 200 kHz.  Rated distortion is 0.02% at 150 watts into 8 ohms, and 225 watts into 4 ohms.  They measured over 400 watts of dynamic power into 4 ohms.

OK, so I know most subjectivist audiophiles aren't impressed by such measurements, but they are very impressive to me.

It is of course the Jim Strickland Trans Nova design, with help from David Hafler.  Two of the greatest designers in the history of audio, and this (along with the Hafler 9500 and 9505) are the last Trans Nova amplifiers built by the Hafler company.  Hafler was a longtime friend of Strickland and he loved the Trans Nova design, a big part of the reason why he bought Acoustat.

Fosgate rebranded the Hafler 9505 as a Fosgate model after they bought Hafler.  Another endorsement.

All the Trans Nova amps will drive anything, and especially Acoustats of course which are about the hardest "4 ohm" speaker to drive ever made.  But these are the last Trans Nova amplifiers, and probably the best.

The 9500 and 9505 are the big versions, with about double the power.  They command significantly higher prices.  The 9500 got a rave review Stereophile, and had stellar measurements also.

Then I looked at the schematic, and knew instantly I had to have this amplifier.  It is simple, and perfect!  Check this out:

3 stages, can't get lower than that without compromises.

Dual diff amp JFETs in front.  The optimum circuit.

Bipolar drivers.  Also the optimum.  Substantial current gain is required to drive the capacitance of the output stage.

MOSFET outputs in the Trans Nova design that drives anything, with no protection circuitry needed.

My friend Tim was blown away as well.  He suggested it could well be my best sounding amplifier.  He noted the very low feedback (remember the rule, you either want very little or lots and lots...this is the very little side).  He noted the lack of emitter resistors on the outputs.  Normally those are required for thermal stability...but because they add additional feedback they actually create a bit more distortion.

Somehow this amp gets away without the emitter resistors, but still drives anything, with low distortion.

A miracle that hardly anyone noticed.  Except that if you search for reviews by people who have owned 9300 or 9505, they say it's the best they've ever heard.  People puts lots of effort into refurbing them (the low profile capacitors were custom made and can only be substituted with more smaller caps on a circuit board stuffed in) and then say afterwards, it was well worth it, the amp is so wonderful.

So now I have a simple amplifier to try.  Probably as good as any by Pass, or maybe better.

This is not your father's Hafler DH300, a good but fairly standard amplifier.

This looks like it may be the crown jewel of simple yet capable amplifier designs.

And, it must be great for driving Acoustats.  Some of the Pass designs are not, especially the simpler ones.









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 or higher (the 496 goes from 1kHz up to 1800 Mhz, my old HP 3580 only goes to 50kHz).  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 even the boat anchor pricing goes up another $1000 or more for spectrum analyzers with 2Ghz and above response--those microwave analyzers are still in heavy demand by professionals.  There's much less professional concern nowadays with mere VHF and UHF, so analyzers limited to that range are comparatively cheap.

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.

Here is a tutorial and video on the Smith Chart often used for understanding antennas.

Here is Paul's Antenna Attic about FM antennas.  I have an APS-9 and Radio Shack 15-2163 still in their factory boxes.  Sadly those will have to wait until I get some help installing them.  Whips are a comparative snap to put up, except for correctly handling the grounding which should be done by an electrician.

Measuring a trap using Sark 110.

List of Pirate Radio Stations on HF Underground.

Sherwood Engineering's tests of HF receivers.

Hardcore DX on HF (aka Shortwave) stations.

Factory brochure on Tektronix 496.

"Super Antenna."

Dave's Shortwave Receiver List.

Roger Russell's McIntosh Loudspeaker History, Part 2.

The Audio Expert (Ethan Winer).

Audio Myths workshop at Audio Nirvana Resources.

The JBL SA-1600 complementary symmetry amplifier reviewed by Julian Hirsch in 1966.

Best Antenna Analyzer for the money.






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.