Saturday, August 12, 2017

July/August Recap (up to August 12, with Audio Party on August 13)

1. Did final and definitive test showing that both Acoustat speakers were actually OK, and spare interface was not OK even if treble transformer was disconnected.  So ordered and have now received replacement HF and LF transformers to fix the spare interface when I have time.  Years ago those replacement transformers were unobtanium--so best get now while the getting is good.  Michael Savuto at Analog Associates is now the source for replacement Acoustat transformers now manufactured by Galaxy Transformers who makes them to the original design.  I contected Galaxy first, and they told me to contact Michael, who was helpful and gracious.

2.  Changed Acoustat fuse values to 3A slow blow,  first with fuses from the last Radio Shack store which was soon to close, and now with HiFi Tuning Gold Fuses from Parts Connexion.  3A is latest recommendation from Roy Esposito, and he says it was actually the first recommendation from James Strickland who reluctantly increased to to 5A to reduce nuisance blowing at dealers, but post 1985 high power and high current amplifiers are now capable of blowing the transformers faster than a 5A fuse will blow and do so all too frequently.  I was disappointed, however, that Roy flatly refused to work on my modified Acoustat interfaces.  He told me he un-modifies any such modifications (external polypropylene crossover cap replacing the original electroylitic capacitor inside) without warning, AND he seems to think I'm dangerous or something for even thinking about fuse-less operation.  I don't think he understood me that I have never myself operated Acoustats w/o fuses, but it seems many famous Acoustat users have, and I was merely trying to suggest in my email that those people should at least temporarily use fuses when testing new equipment, which I do often, and which specifically led to my latest failure, I thought at the time.  I did not know at the time that my original interfaces were actually OK.  As dangerous as I might be, now it appears I have not damaged my Acoustat interfaces in 7 years, and it's quite possible the one I broke in 2010 had actually been broken by a previous user.  Also I renewed my understanding of the interface and thought a lot about other interface modifications, reading about half of the Acoustat AnswerMan thread at DIYAudio, where lots of people have done a film capacitor substitution similar to mine, and Andy Savuto, former Acoustat engineer, thought it was an excellent idea.  Reading that forum there are many many people who have done far more risky modifications than I have.

3. Hooked up and tested the Eagle 2 amplifier, quickly deciding that it is indeed very special, as I remembered from 1988.  But under-current and/or my unit needs work.  Purchased two more Eagles for High Current (one of two options) mono conversion.  Tested one of these and it stated snapping inside--it needs work!  Learned a lot about Eagle options, etc.  Now I see why there is a 7, but mono'd 2's should work for me as the output level is ok with 2's, they just need high current mono conversion to deal with impedance below 2 ohms.

4.  Purchased cheap Integra Research RDC-7.  But turns out to be dysfunctional.  I'm now thinking Denon's quality level is at least as high as Integra Research in Denon statement models like DVD-5000.

5.  Mass tested DACs using RMAA, reaching some new conclusions.  Also tested time delays---they must be controlled I see now.  Determined conclusively my Master 7 needs repair.  Decided that Denon DVD-5000 looked to be the best of my remaining dacs, so I bought another one.  Now have two Denon DVD-5000's online as mid range and super tweeter DAC's.  Also got second Emotiva Stealth DC-1, the first one measured best of all distortion and noise.  But that is now a backup.  Considered getting third DVD-5000 (I could have them on all 3 ways, but would give up XLR digital and XLR audio connections unless I got an additional amplifiying device, so lots of extra space and complications).  Forgot to increase bid and lost out on incredibly good deal on one with 14 day guarantee.

6.  Set up Laboratory (2nd bedroom) for first time in 6 years.  Finally cleared big toolbox from bench by buying and putting up a rolling support rack for the toolbox instead (just as mechanics do, and it was my ultimate plan from a decade ago, but there had been many delays until I finally recycled some boat anchor equipment in December).  Set up RMAA computer on top of bench and continued doing RMAA testing there, using Emotive XPS-1 as buffer amplifier.

7.  Tested old DVD-9000, which I had previously determined to be my best sounding player, as my living room mid way DAC.  Sounded great but it is too much trouble to keep adjusting delays for each sampling rate, and needs huge 330 msec latency adjustment at 44.1kHz which requires putting 3rd or more DEQ online because each one can only compensate for 300 msec.  Bought second DVD-9000 which is fully functional, including DVD-Audio.  Put the new DVD-9000 online as my new HDCD/DVD-Audio player to replace my original DVD-9000 which was unable to play DVD's at all and is now offline.  Set menu settings on the DVD-9000 for best 2-channel use.  Also strangely the DVD-5000 measures 15dB better S/N, though DVD-9000 has slightly lower distortion according to RMAA.  That held true for both 5000's and both 9000's.

8.  Determined my Integra Research RDV-1 as a CD transport has my best jitter performance and I am now using that for CD digital, which sounds great!  Not long ago, I would rarely even do this, always ether resampling or playing off my harddrive.  The RDV-1 does not have as good S/N from analog output as DVD-5000, but it has 2.5 times less jitter than the DVD-9000 as transport.  Actually the jitter from the RDV-1 measures 180 psec, which appears to be the limit of SPDIF itself, or my Sencore jitter meter, since I have never seen it go lower than that, you could call that my "residual" (though I'm not actually sure it is, the Sencore is marked down to 20ps but nothing I've measured has been lower than 180ps, what I measure for the RDV-1).   The DVD-9000 measured 500 psec at the SPDIF output, somewhat disappointing, but at the analog output it is probably internally synchronous so there is little jitter in that.  After testing, I restored the hockey tape insulators that help silence the noisy RDV-1 drive system, which is not especially quiet and noiser than most CD players when playing CD's and there's no fancy "seal" system like many pricey players.  But with my hockey tape, it's no worse than the typical CD player.  The RDV-1 boasts a clock by Apogee, likely that is far better than most players, and when using SPDIF and AES as the system interconnection method, everything past the transport must follow the clock of the transport in some way, so it's arguably most important (a DAC need not even have a clock, in principle, just a pll locked to the incoming data stream).  BTW my Denon DVD-5000 dacs use the Crystal Semiconductor CS 8414 input receiver, which is fully synchronous.  I like the idea of synchronous.  However the newer DIR9001 synchronous receiver has an order of magnitude lower internal jitter (from 200 ps to 20 ps) and may have better jitter rejection as well, though the 8412 and 8414 were highly regarded in the late 1990's when the DVD-5000 was made.  (The 8416 was considered somewhat inferior, and some consider the 8412 the best of all.)  When I tested jitter at the very end of many digital interconnections in my very complex system, it was still only 220 pS or so, regardless of source, if I ultimately used coax...I've never tried that using a Denon as transport however.  Presumably a DAC could reduce that to essentially zero above 1kHz with only 1mS of latency with well tuned PLLs.  It might already have been reduced by the Tact or Behringer, which have their own PLL's.

9.  Determined more-damaged-looking left Elac ribbon super tweeter had 14kHz resonance (evinced by long decay on RTA) and perhaps others, contributing to metallic sound.  Researched new ribbon, dome, and other super tweeter options.  The smallest RAAL looks most interesting, uses flat foil damped with etching and has response to 100kHz, and looks very (if not perfectly) clean in decay waterfall.  But for now I bought two Vifa NE19VTS tweeters, and cobbled together a bipolar super tweeter box with my old (and best of all) Dynaudio D21AF's in front, and the new Vifa's in back.  The back supertweeters seemed essential for best result.  Cobbled together crossover and adjustments for it also.  Much experimentation demonstrated how the supertweeter adds missing "power" to the sound, strangely adding a sound very much like when I had the Eagle 2's playing the Acoustats with no super tweeters.

When I turn the super tweeters off, the system sounds wimpy.  And yet, I can barely hear anything coming from the new super tweeters if nothing else is turned on, especially after I've made the cutoff much steeper in past couple months.  New Hakko soldering iron worked very well to set up the new blocking capacitors for the two tweeters, and I've done more soldering already this year than most of the past 30 years.  So what is going on here?  Is it a physical effect, perhaps some sort of summing going on in the air itself.  Or is it some process going on inside the brain alone?  (Or am I just imagining that I even hear an effect...I'm not sure I want to know.  I certainly don't want to bother to try to prove it yet.)

10.  Verified that Krell FBP 300 right channel was not working correctly.  Checked freight rates at a different company first, then chose Ocean Air again.  Packed and shipped it out.  After trying Eagle 2,  and having it shut down twice, I set up Aragon 8008 BB as current backup amplifier.

11. Found that off tuning certain stations, including KRTU and KSYM, by +25kHz, gives best result.  This, along with sampling through Lavry AD10, has dramtically improved FM radio sound, even on "oldies" FM stations and the like, sounding better than ever, and somehow similar to the sound of the Marantz 20B on those oldie stations.  I think the off tuning enhances rejection of on-channel alternate station.  Rejection by off tuning with Wide bandwidth does something good that Narrow never does, and I think it's related to capture effect, blocking on-channel or adjacent channel signals.  I had always thought the 25kHz L-1000T tuning to be inadequate, but in fact it works great.  I never had such a clear win with the 10kHz tuning of the Yamaha T-85 years ago.  Kenwood engineers seem to have picked the perfect off-tuning amount for their detector.

12.  Researched cartridge loading.  IAR suggests going as low as you can, 5 or maybe 2 ohms if possible, with lowest impedances reducing IM, if you can deal with the level reduction.  I was using 470 ohms, so I tested the 100 and 47 ohm settings of my XPS-1.  I determined that 100 sounds best, and that 47 ohms both reduces the level too much and makes it sound slightly strained.  I also changed tracking force from 2.2g to 2g and re-leveled turntable.  Also oriented XPS-1 (now held in place with with hockey tape) and moved the 220V transformer for L-1000T further away, reducing hum as much as 20dB so that hum and noise are now below -80dB rms in both channels at 97.7.

13.  Used Tact measurement mode to adjust 3 way time alignments, first time in at least a year.  Was difficult to see exactly what to do, and I need a better program.  Also did many, many adjustments to PEQ's, levels, and time delays, which yielded far flatter response, more solid bass, and sweeter highs.  Did adjustments based on 1/6 octave RTA app and Stereophile pink noise mainly, and when things didn't sound good I made more changes until it sounded good.

14.  Tested new Marantz PMD661MkII digital recorder, recording the output of the Lavry AD10 digitizing the output of the Kenwood L-1000T playing KPAC which was playing a local pipe organ concert.  This may be a far easier way to make digital recordings from FM radio and vinyl than the Masterlink, primarily because I can upload so easily to my computer afterwards.

15.  Digital from the kitchen Oppo reaches the living room system fine when using the DVD-5000 Dac's.  No issues on any disc tested so far, except that SACD, which is supposed to output 88kHz when PCM mode is it not going through.  But playing the HRx discs from Reference Recordings at 88kHz works fine.  I discovered back in May or June that I could actually do that now, for some reason, unlike the first time I tried in 2014, and it has been a boon.  That means I can play any disc with high res files on it.  But I still need my 9000ES player to play SACD's.

16.  I've been discussiog preamp designs with my friend Tim, and I bought a very expensive book by Vogel on solid state phono design.  We've both become very interested in balanced phono stage for MC, which should reduce IM.  I read about the Vacuum State Electronics balanced preamp design and was fascinated by the ideas used.  Tim felt that the tubes were not usefully deployed in that circuit, and would be better replaced with OPA 211 circuitry following the initial amplification device, for both greater linearity and lower noise.  We've been discussing impedances, use of transformer, etc, etc.

17.  Reading about jitter, obtained but barely started reading the Dunn paper for AP.  Bought two books on acoustics, one by Toole.

18.  Added, yet again, infrared remote capability to control my L-1000T and Tact 2.0 RCS from the kitchen.  The L-1000T is pretty reliable, the Tact less so.  This is simply a placement of the Radioshack IR extender transmitter in the living room bookcase.  An idea I somehow hadn't thought about before.  I tuned up a bunch of stations into the L-1000T memory.

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