Subwoofer back, and limiting adjusted

I finally got around to replacing the plate amplifier on my SVS PB13 Ultra subwoofer with a new one purchased earlier this year from SVS.  The original plate amp was from 2008 and was not under warranty, but I was happy to pay for this new unit, which looks excellent (and actually looks better made than the replacement for the other channel I got a couple years ago).

And it works great on the new dedicated circuit, and there is no hum or noise aided by the balanced connections from my Emotiva Stealth DAC.

Perhaps it's just because my ear has become more sensitive to bass distortion after 6 months of using the Acoustats with no subwoofer, or my subwoofer driver is ageing also, but I noticed after awhile that more limiting was needed to avoid serious bass distortion on some torture track recordings, such as Bass Connection.

I was already using a frequency selective limiter and the lowest frequencies (in the Behringer DEQ 2496 that serves as crossover and eq for the subwoofer channels).  I had set that up before. Actually I don't think I understand that and may need to re-read the documentation.  For now I set up a standard limiter function, somewhat more agressive than before.

After listening to torture track recordings over and over I adjusted all the limiter parameter for both the standard and frequency selective limiters.

I had figured the limiters in the subwoofer itself would be good enough, but they are clearly not, especially with the new amp (is it tuned correctly?  I did set the type correctly to "sealed") and dedicated circuit.

I am thinking now that pretty much all practical subwoofer systems intending to achieve bass below 30Hz need to include limiters if they are going to provide something like flat response, to deal with different kinds of recordings.

I believe previously I was very messed up about setting the bass level, sometimes setting very weak bass to allow my torture track recordings, then playing those recordings and causing ceiling cracks and turning it back down again.  Now I seem to achieve precisely the desired effect with limiting.  If I play at modest levels, the limiters have absolutely no effect.  Only at super loud levels do they kick in, and still sound fairly good when they do (because of my clever adjustments), just somewhat softer than the bass might otherwise be at those super loud levels (still loud enough).  And it was actually sounding quite distorted and horrible when those higher levels were being "reached."  I had just been ignoring that apparently, and enjoying the "BASS, Man."

Read on my RTA app at 1/6 octave resolution, my bass is as flat as it has ever been, very little room curve bulge, but slightly decreasing down to 20Hz.  And yet sounds plenty loud, but far more musical than ever before, notes rather than booms and rattles on the torture track recordings.

Krell finally fixed by The Service Department

My Krell FPB 300 has been fixed, refurbed, and upgraded, and it is working perfectly for the first time ever, thanks to Steven at The Service Department in Connecticut.

I had sent my unit to the Krell factory on 3 previous occasions, and never did they get it this good.  There was always a significant thermal difference between the two channels, like one channel at 180F and the other at 140F, according to my IR measurement technique (which might not be accurate, but fairly repeatable).

Also, it always used to make a "clink" sound (what the service people call "ping," but mine were so loud, they really were clinks and not pings) frequently, like many times per hour.  After the latest repair/refurb/upgrade, it has hardly made any in a week, and they've been mostly soft.

I also credit myself for insisting on having repairs done to both channels, and for insisting on replacing every suspect part, including the relays and XLR jacks.

NOW, both channels track within a few degrees, reaching reasonable levels like 150F for moderate to loud playback, 140F for low levels, and up to 168F for really really loud and sustained.  Previously it had been going over 200F in one channel.  My belief is the Krell is designed to force the 2nd lowest plateau when the temp goes to 180F (it is designed to handle the heat) and shut off at 200F.

And it sounds even more transparent and dynamic, thanks to the refurbs such as replacing the power supply capacitors, which even the factory "capacitor service" did not do, and upgrading the front end to the 400cx design.

The program was changed previously (by the factory) and now my front end has been upgraded (perhaps these two changes anctually should have been done together???) so I basically do have a 400cx now, except for lacking the CAST input, which I would not be using anyway.

Now, more than ever, there may be a chance for a history making ABX in comparison with the Hafler 9300, which also sounds excellent and perhaps sweeter, but is even farther from the dynamics and transparency of the Krell now.

Another mistake fixed

Though many times I think I examine situations far more carefully than others, and think about them far more deeply, nevertheless I often make mistakes.  Big mistakes.  Not long ago I had my system speakers "out of phase" (with each other) for over a week.  In my defense, the audio specialist at my house immediately declared the phase was correct (though it wasn't), and after he left I played music almost entirely in background until discovering the problem.

Recently I made another discovery that pretty much invalidates all the comparisons I've done since February when my 2nd and 3rd dedicated AC lines were installed.

Last week on staycation I discovered there was (barely) audible hum coming from both speakers.  I immediately realized I had not followed through with the plan to put the DACs for the main amplifiers on the same circuit as the amplifiers themselves.  (I have separate DACs for the two amplifiers so I can level match each amplifier in my now permanent ABX configuration, with zero degradation as compared to what I would be doing otherwise, it's just the same thing but now in parallel, nothing was added in series except upstream there is a AES3 digital splitter which I'll say more about later.)

So, I did that, and at first the hum seemed to almost entirely disappear.  I had remembered it being nil in the past, with ear right up to the speaker I could hear nothing through the Krell and Aragon (when everything was on the one dedicated circuit).  Now it wasn't quite nil, but so low it could only be heard with ear to speaker.

Then a few days later I realized the hum was still louder than it should have been.  So I tried also putting the AES3 digital splitter (the digital output of the Behringer DSP is split for the two dacs which feed the 2 amplifiers) also on the same circuit as the amplifiers.

With this change, the hum vanished entirely.  Zero, nada, zilch, with ear right to speaker.  So this is what I'll have to do (I'll need a small power strip for the 2 DACs and the splitter because the wall has only 4 outlets on this--the original--dedicated circuit and there are already 5 things that need to be plugged into it).

Given that AES receivers are transformer coupled, I'm not at all sure why the AES splitter needs to be on the same circuit.  I think the AES3 isolation in the Emotiva Stealth DC dacs is not as good as my Henry Engineering (HE) AES3 splitter--which seems as solid as anything could be, and this is more evidence as to how excellent it is.

BTW in earlier tests I found that the HE splitter added no measureable jitter to a digital signal as analyzed by my Sencore Digital Analyzer.  In fact, that was true of my entire digital setup starting from the Sonos Connect, through the long coax cable to the Tact RCS 2.0, the Tact itself, the cable to the first HE splitter, then to the midrange Behringer unit, and the cable leading up to my Audio GD DAC 19.  I measured the same 220ps jitter at the Sonos output as at the cable connecting to the DAC 19 going through all those pieces of equipment and cables.  This convinced me at the time that 220 ps was just the "inherent" jitter in SPDIF, given the nature of the signal and the impedances, there is just enough deflection of the baseline to cause that much jitter.  Well, I was wrong, I've now measured the lowest ever (for me) jitter at the output of the Oppo BDP-205, actually playing the tougher J Test signal, where IIRC measured under 200ps, 190 or so IIRC.  Now I think THAT is probably approching the inherent SPDIF limits on J Test.  My meter can reliably measure as low as 150ps, which I did using white noise (as I did in the aforementioned full digital system test reaching 220ps) using the Integra Research RDV-1.  Using the tougher J Test signal, the RDV-1 measured about 210ps, not as good as the Oppo, and we would expect the Sonos to rise above 220ps a bit.  Anyway, at the time, I was pleasantly surprised by the low jitter (none measureable) added by my entire "complicated" digital processing system.  And I should add I don't believe jitter as observed in typical audio systems to be of major importance, experiments should it to become important at levels 10,000 times larger.  When I was using Toslink, I could not measure the jitter reliably, the Sencore wouldn't show any numbers mostly, but finally after much fiddling and conversion back to coax I got it to show 600 ps.  That's when I decided not to use toslink in my main system for serious sources, though I still doubted the jitter added to be audible.

Now, with separate AC circuits having a boundary at the HE splitter, some might suspect I'm adding jitter.  It is the input to the HE splitter which must reject the ground loop at the ground at its input.  If it does so imperfectly, SOME of that ground difference might be impressed onto the digital signal, causing jitter.  This is in spite of the splitter having a transformer coupled input which rejects hum by 80dB or more, and in spite of AES3 being a balanced signal "unaffected" by ground loops, and in spite of AES3 being a signal with 2-7 volts PP.

So, one could argue, I've eliminated the analog hum, but I've replaced it with a trace (and it would be barely a trace, for the reasons I just gave above) of jitter.

It's worth doing another jitter measurement anyway, but I suspect the jitter is negligible, and even if the splitter were adding jitter signal, it would then be almost entirely eliminated by the asychronous receiver in the Emotiva DACs.

Sonically, it is better than ever.  But now the slight physical hum from the Hafler 9300 chassis became noticeable, so I tweaked it using a 3 piece set of Mapleshade Heavyhats (which I had still in factory box waiting to be used, I had intended to use them on DACs).  This seems to help, though I wonder if it's mainly caused by expectation bias.  Strangely, I now can't hear the hum from a couple feet away from the Hafler, but inches away it seems about the same.

I also tweaked the speaker cables using 4 CableElevators I bought recently, lifting them well above the power and digital cables.  I bought an 8 piece set of CableElevators, something I'd lusted for about 20 years, on sale.  These don't fall over like other lifting devices, and present several surfaces where cables can be delicately perched as well as the main central grove.

Audiocheck

A friend sent a link to this collection of audio tests:

Audiocheck.net

Turntable Peripheral Clamps (aka Rings)

Clamping records at the periphery has seemed to me like a good idea since the first I heard of it in the early 1980's.  I'm surprised it hasn't caught on more than it has.  Center weights and clamps have definitely caught on.  It seems like all serious audiophiles either:

1) Have a center weight or clamp on their turntable

OR

2) Own a Linn or Rega and have bought the non-clamping ideology those two firms promote.


I know relatively few people with Linns or Regas anymore.  And curiously all those people I do know...which includes myself...are fully into clamping nevertheless.  With the one exception of the Linn guru Mark who was once a dealer.

I will say that if you are not listening "seriously," just background listening or dancing, non-clamping is more convenient and even sometimes lends itself to background listening (because more highs) and dancing (more percussive sound from record resonances).

So, I've decided I will not always bother to clamp, even though I believe it sounds Much Better generally speaking.

And I'd like to take it to the next level with peripheral clamps, sometimes called "turntable rings."  From both my intuition, and limited experience (I heard the R.E.A.L. once)  I strongly believe this is the way to go.  While center clamping, it's always bothered me that the edge of the record wasn't getting much if any help, or worse.

There is a VPI stainless steel version, which sells for $999.  VPI advises that you not use this on many VPI models until you upgrade the platter and bearing to the HRx level.

https://www.musicdirect.com/analog-accessories/vpi-periphery-outer-ring-clamp

Wayne's Audio in Pomona California has two "universal" models for $599 and $699 apiece:

https://www.waynesaudio.com/shop

Merrill sells their ring clamp for $850, or part of $1200 set that includes center weight.  It is not clear if these are suitable for other than Merrill turntables.

http://www.osageaudio.com/merrill_williams.html

I'd like to have Merrill's version most of all...as he really seems to understand turntables and resonances and clamping the best from decades of experience.  And I'd like to have a Merrill turntable to go with it, either a R.E.A.L. or one of his previous designs.  But, understandably, his version is the priciest, and the tables aren't cheap either (except relative to performance compared with other tables).

Observations on the LP12

1) Is it the most tuneful turntable I've ever heard?  Yes.  And I appreciate it for that reason, though as one person once said, no turntable is perfect and therefore you can never have too many turntables.  This "tunefulness" is not entirely a matter of superior speed constancy, I believe, but part of kind of pleasant coloration not entirely involving rotational speed but also high and lowpass filtering and/or combination with resonances.  The speed, for it's part, varies as much or more than other premium turntables, but it varies in a peculiarly slow and pleasant way that sounds natural and relaxed.  I'm thinking it might vary around the same speed as the effects of off center wow, possibly sometimes cancelling the off center wow, and otherwise being masked by it.  Other turntables may vary speed in a more abrupt, forced, and mechanical sounding way.  Of course I'm talking about tiny variations that are not easy to hear, especially in the case of the Linn.

2) My LP12 Vallhalla with Ittok LVII (does LVII mean 57 ?  like Heinz ketchup ???) arm, seems to have a slightly over-brightish quality.  I think the largest part of this may come from the quite noticeable metallic resonances of the stainless steel tonearm (with the funny name not coincidentally made to sound like "I Talk" ???).  Those resonances could be damped, and otherwise I think the excellent pitch and bass produced by the arm indicates that it has marvelously tight bearings, which is one of the hardest parts to get right in making a tonearm.  So this is a good tonearm which could be made even better, I believe, by getting past the designer's religious convictions against damping.

3) My belief remains in harmony with a majority of high end audiophiles that in principle records should be clamped (or otherwise held close to) a highly absorptive mat.  The Linn felt mat is only partly absorbtive--but it may or may not be part of some mysterious "synergy" with the rest of the turntable.  Clamping on the Linn is made difficult and less useful by many factors : the loose suspension, which quickly bottoms rubbing the aluminum platter on the stainless plinth top when trying to apply the clamp; the low spindle, requiring round-the-platter checking for level balance if the clamp--like the Michell clamp--has no level and doesn't deal well with low spindles...I suspect most if not all clamps would have a problem with it, and clamping it might not do entirely the right things here with the thin felt mat and undamped platter, reducing much of the felts isolation properties between the platter which is ringing from many things, including the bearing and the vinyl, and the record.

At minimum, clamping should be done with a different kind of mat, or combination of mats.  And it's too much trouble on the Linn except for the most critical listening or transcription.  It is nice how tuneful the turntable sounds without taking such bothersome measures.  It could be regarded as a kind of "convenience" turntable, much the way audiophiles thought of CD's when they were introduced.

Update:  With NO metal washer, and a 180g pressing of Blood on the Tracks, the clamped version was clearly better.  I did the claming in one careful press, not needing to verify the flatness until afterwards, by releasing and spinning, which was much more convenient than the previos pressing down at each slight rotation.  Both ways it was flat around the edge, in fact the claming didn't seem to have much direct isolation at that point, but much more isolation through the rest of the record.  (A Merrill-Williams type perimeter clamp...Merrill's innovation since the 70's...would be ideal but impossible on most tables, except those designed for clamping or vacuum...I'm now thinking perimeter plus central weights as Merrill does may be better than vacuum--quieter.)

Unclamped it was harsh and edgy, clamped it was cool but highly transient.  Clamping was the clear winner in realism, pleasantness, spaciousness, musical interaction.

Unclamped was that old "tuneful" simplification, as Arthur Salvatore says.  He doesn't say it comes from clamplessness but I'm thinking the clamplessness, even with old Linn mat being used with the clamp, must account for 80% of the familiar tuneful (de-complexifiying) coloration goes away.

Now at least one would think it wouldn't have much impact on timing.  Though, BTW, the Linn and most belt drives are host to a myriad time issues.  For the Linn, setting the speed is a final setup step.  It stays as good or bad as that...at least under indentical conditions and the belt hasn't passed some aging threshold.  But if that were not done, it would be hopeless, as the timing depends on the precise angle of the chassis and subchassis, which in turn is determined by the mass on the platter and armboard, for starters.  But then in actual use...all these things are still somewhat varying.

It seems to me the LP12, just becuase of the suspended belt and pully and subchassis design, is doomed to a sort of slow varying imprecision.  It's only "tuneful" however because it's so slow as to not actually be objectional, just slightly making everything different each time.  Other systems like ider and direct drive are more "locked in" by high torque control systems, belt drive is constantly resonating the drive frequency of the platter at the fundamental frequency of the belt system, and possibly others.  Imperfect perhaps, but the choice of so many phonograph users for so long...it can't be that bad...and may have some advantages.  Which is why I want one, and choice units of other kinds.


4) Now I'm thinking, much as I have before, that a vacuum hold down system is the best of all, and it can be had, though at higher prices than I paid for the Linn, but that's an unfair comparison because I did not buy the Linn Valhalla with Ittok brand new either.  On similar terms, the Linn and Sota turntables with vacuum are priced fairly competitively in the USA.  On these terms the highest end Sota Millenium is far less expensive the most fully loaded Linn Radikal ($10k vs $20k), with similar differences down the line.  This matters if you consider them comparable, which you may not.  I'd last heard of Sota in the 1980's and was thinking they were long out of business but no, they are still selling and servicing servicing older turntables too.  That's a path I'm still somewhat interested in, as other vacuum clamping turntables are much more expensive.

I might try to trade my SP 10 for a Sota, but the ultimate ultmate would be a fully refurbed SP10 with vacuum holddown added.


4) Anyway, the special characteristic the Linn imparts as a result of drive operation, foremost is non-correlation, where no radial part of the platter has a tendency to raise or lower pitch even slighlty.  The pitch may be wavering, for sure there is wow and flutter just as in other premium turntables, but it is non-corrlated.  Direct drives have wow correlated with platter position, as shown by graphs published by a Linn lover (who conveniently didn't disclose the scales on the platter rotation dependent wow, making you think if the scales were equal, the better direct drives might be so low anyway the platter dependency shown was a small issue).

As well the Linn has olympian isolation from the environment, mostly.

Direct drives are somewhere in-between, with finer grained platter rotation dependency mostly.

Does this matter?  I am beginning to think the rotational constancy IS the most important factor, and it's not perfect in any turntable, the Linn just hides the imperfection better than most.

With regards to the initial transients, it all comes down to effective platter inertia.  It's follow through that is determined by the drive system.  The belt drive takes it's time to correct, ultimately averaging out.  The idler whell corrects immediately and perhaps too abruptly.  Direct drives may vary with implementation, but in principle can respond faster than belt drive, but perhaps not as fast as idler wheels.

So, if there is a superiority of idler wheels in the attacks of music, it's all in the follow through, in microscopic terms, though you might not hear it this way, the "follow through" begins microseconds after the initial transient, for which the platter inertia is everything, and the failure to correct begins appearing within the minimum audible time interval.

MQA unmasked and denounced

I was shocked to read the findings of Archimago (a trustworthy and reasonably open minded objectivist audiophile) about MQA.

It looks like if there is a difference in the sound with MQA, it's largely produced by an increase in aliasing artifacts.

As Archimago argues, we don't need MQA.  We have MP3 for those who don't care about quality, standard resolution formats, and high resolution formats for those who want the highest possible quality, and they are all open formats.