VAC - any comments? Good or bad.

I am considering buying a set of VAC amplifiers. I have read comments on other companies before her in the forum section, but have never read anything on VAC. Anybody got anything good or bad to say about these guys? Thanks for your comments.
My impression has always been that VAC makes incredibly musical gear and has top-notch quality. Their least impressive models over the years have tended toward marked warmth for what its worth.

The usual complaint about VAC gear is $$$$, but there is more expensive gear out there watt-for-$ and I have always had great respect for VAC - especially their top of the line stuff. I am actually waiting to audition the PHI 70s in my system and see if they have enough power. I've got my fingers crossed b/c I love what they can do in some systems...

BTW- I have nothing to do with making or selling audio gear, so my ears are my main bias!

What are you looking at buying and what is the rest of your system? Everyone will ask, so you might as well get this out of the way up front.

If you can, listen to the VACs in your system and see if they do it for you - they have been truly magical in other setups I've heard!

Good luck,
Unbelievable build quality and musical presentation. That sums it up. I have owned various VAC linestages, pre-amps and amplifiers over the years, the latest and current being the 70/70 III amplifier. I can tell you that you absolutely cannot go wrong with ANY piece from VAC.
TAS has had great respect for VAC for a number of years.
Thanks for the comments guys. I have heard VAC amps in the past and have been very impressed with them. I am looking at buying a set of monoblocks that are no longer in production. I was looking more for info on what type of company VAC is... ie, are they easy to deal with, do they support their older stuff, will they offer help to make their equipment better. I have heard glowing comments about companies like Atma-Sphere and Joule, about how their people go out of their way to be supportive of their equipment and was just wondering if VAC is that kind of company. I was hoping to hear a few war stories about people's experiences with the company itself and not so much about their equipment.
I OWN A vac AMP AND KEVIN OF VC IS VERY NICE TO DEAL WITH. hE DOES SUPPORT his product old and new...just give him a ring....
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I will echo Ryriken's comments about VAC suppottin their older gear. Kevin is very responsive and enthusiastic. Don't hesitate if you have an eye on used VAC gear.
VAC is a great company. I own a discontinued linestage preamp and Kevin has been very helpful with suggestions. He even helped me figure out a problem that ultimately stemmed from another non-VAC component! I don't think you can go wrong with used VAC gear. Good luck.
Count me in as another happy VAC owner. Before I bought the Standard PRE LE, I had a couple of conversations with Kevin and found him very sincere and pleasant. He didn't have that "salesman pitch"--I know 'cause I've been in retail for more than I can remember.
I can't say enough about the fit, finish and sound of my PRE.
Earlier this year I got the VAC PA100.100 and a Standard Preamp LE edition. Even though I bought these both used, Kevin emailed me to welcome me to the VAC family. He really is a great guy to talk to. The PA100.100 is near their lowest model in separates and is simply a great and underrated amp. I paired the VAC with the Merlin VSM-M and am loving every second of this wonderful pairing. I've always lusted after VAC because it just seemed like beautiful gear that had a great reputation for sounding excellent. I agree now that I'm in the family.
I too expected only good things from my first use of a VAC amp, and lugged home a well-broken in VAC Avatar a few years ago. The long story is somewhere else posted. Suffice it to say that it's horrendously high output impedence wreaked havoc with my newly-aquired Parsifal Encores (which are VERY easy to drive, btw), with disturbances as much as
+/- 5dB across the spectrum, as finally carefully measured
against two reference amps. Horribly overripe mid-bass, a giant low treble peak and no upper treble "air" made all discs unlistenable. I faxed curves to VAC and was finally told that the inexpensive AVATAR's output tubes were famous for nonlinearity and unpredictable results with real speakers, and that if I wanted really fine performance I had to get their bigger amps. Sad to say the Audio Refinement Complete ($995) I had on hand absolutely trounced
the $3800 Avatar in both triode and pentode modes.
I then came to look as Stereophiles "predicted plot" of real performance with an 8 ohm load with glass amps once in awhile in JA's reviews, but NEVER saw one with swings of the amplitude I measured (and many of us heard) through that Avatar. And yes, both channels were the same, the tubes were ok, power output was correct, etc.
Glad their higher end stuff is more linear, and that they've recently completely redesigned the 'tar.
I have had nothing but wonderful experinces with VAC. I can't imagine what this prior post is all about. What kind of measurements were they taking, and with what gear? Is this just proof that there is always someone????
Ten posts, now eleven, and, one crucifixion. Sounds about right; everyone loves VAC and Kevin then the expert steps up to the plate and just lays his product to waste. Strange, and not my experience. Except for that time that when my Radio Shack $99. receiver sounded better than the London!
Just a word I'm a happy Avatar owner...I purchased it used with Svetlana EL-34's as the output tubes. I'm running a pair of Green Mtn. Europa's which are tube friendly given their fairly flat impedance curve. Sounds great to me! Mid-range timbre and harmonic structure is right on, great upper end detail with no hardness. Bass is as one might expect from a monitor. If it's an indication of VAC products I wouldn't hesitate to purchase their other offerings.

Ease up on Subaruguru, guys. He's jut reporting his personal experience with product, not making a blanket indictment of the brand.
Exactly! VAC's techie admitted that the EL-34 in the original AVATAR was quite unruly, though with the relatively benign imp curve of the Parsifal Encore I expected better linearity. As I remember the deviation:
Down a couple dB in lower bass, climbing to flat at about 60Hz, continuing to climb to maybe +3dB at 100, falling to a big trough at 250-400 or so, then climbing steeply to a BIG peak of about +5dB at 4k, then dropping ike a stone to -10k at 20k. Can you say screechy horns and bloated bass?
Whereas the three ss amps (NAD, Audio Refinement Complete, Aleph P+ 2s) agreed within +/- 0.25dB (meter/eyesight noise). Again, this is NOT a blanket disparagement of all VAC products. And although I know nothing of the new version of the Avatar, is it possible that they're using a more linear, predictable output stage with a much lower output impedence? Anybody know? I really felt badly for Julien Pelchat on the other end of the line in in Quebec when I told him what this amp was doing to his careful crossover work! Why bother to sweat driver matching and all that crossover research your design rests at the whim of unruly whipsawing? After I returned the AVATAR tyo the Pass/VAC/Verity/etc dealer he DID admit that it sounded different from all other amps. Phew....
I have a pair of VAC Phi 70s.


Listen to a really good full DSD SACD through these things (I'd recommend Jorma Kaukonen's recent release) and you'll have, well, one of "those" experiences.

Oh, and they're easy on the eyes, too.
Just can't let this one go. What were you measuring? The amp output, or the speaker output in the room? What techniques, etc. Just curious. I spoke to Kevin Hayes personally, after this came up. Kevin is honest, sincere (doesn't mean he couldn't make a klunker) and he is nonplussed by this 'measurement'. So I really don't think unexplained 'scientific' measurements are as compelling as Subaruguru might think. I would like to know more about his process. I am very curious. If someone takes a manufacturer to task, it only seems fair to publish the whole of the technique involved in the 'negative' measurements he obtained.
Also, I would say that, if the Amp measures, independently, this poorly, it SHOULD be published, and the manufacturer, scolded. I do know that the Avatar will play the THIEL 3.6, (a speaker known for its horrific load, and inefficiency)quite loudly, and according to all reports, reasonably flatly in its output.
Again, very interested, and hoping for fairness on both sides.
Hi Larry, et al.
I don't have the actual response data I estimated above at hand, but I did publish it in an (or whatever they're called) review last year or so), and can probably retrieve it somewhere, unless I through it out during an annual office-cleaning last winter. I didn't buy the amp, so there was no reason to keep an old file.
But the methodology's what's important here, and has been used by me several hundred times throughout speaker and crossover design, so that's implanted in my brain:
Radio Shack SPL analogue meter, at listening ear height, just in front of listening position, which is just about configuring a 7.5 foot equilateral triangle, with, in this case, pair of Verity Audio Parsifal Encores.
Sturdy tripod is used, of course, and NEVER moved even 1/8" throughout all trials! (Some of you will know how important this is for measurements in the midband.)
1/3 octave warbles sourced from Stereophiles test discs, as they're convenient, and played on EMC-1 CDP, through Aleph P pre and Aleph 2 monos, through Nordost SPM/RedDawn XLR,and Red Dawn cables. Room is heavily damped, including first reflection points.
Comparison amps included: Acurus whatever $1600 ss amp, Audio Refinement Complete, NAD 7400 (receiver), and of course the Alephs now in place.
Procedure: Streophile disc plays 1/3 octave warbles 200Hz down to 20Hz, then 250Hz up to 20kHz. Full 20-20kHz plots were run for each amplifier. The order being one of the ss first, then the Avatar, then another ss, then the Avatar again, then another ss.
Results: all ss agreed within 1/4-1/2dB across ALL test warbles! Both Avatar curves self-agreed within 1/3-1/4 dB (test self-noise limit given by SPL meter readability, and imprecision limit in midband, as extra care required to NOT move human head).
Again, the difference in non-linearity between the AVATAR and the three near-clone ss amps was VERY HIGH in signal/noise ratio. Now you could say that the AVATAR was right, and the three ss amps were wrong, because the Radio Shack SPL meter is itself not very linear. But listening tests with the AVATAR certainly indicated that many things wre completely wrong, and easily correlated with the data:
the bloated bass, the recessed lower mids, the big peak in the low treble, the severely depressed upper treble.
Finally I obtained the Aleph P and 2 monos, which of course measure like the ss amps, but sound glorious.
FYI. The Parsifal Encores use a 4 ohm woofer, but are said to provide a near-constant impedence load that's easy to drive, albeit not as high in impedence as the original Parsifal using an 8 ohm woofer. I would imagine that the very high output impedence of the AVATAR has trouble with any 4 ohm driver, but again, the amplitude of the deviations I observed, and several of us heard, were shocking. "Kind of Blue", even in cleaned up latest form, was screechily unlistenable! Yes, I was told by VAC to try out their 90-90 or something like that (70?) as an example of a truly linear amp, as they too expressed concern over the unruliness of the output impedence of the tubes used in the Avatar. I'll try to find the review data to the difference plot can be drawn. I wasn't making a mountain out of a molehill here. +/- 1-2dB I was expecting, but 3+ makes a joke of the speaker designer's art!
Larry. I threw out ALL my files save for those pertinent to gear I acually own, BUT I did keep some of the sets of measurements pertinent here, buried in a file of N803 vs Fidelio measurements, as it was the Fidelios that I used, not the Parsifal Encores, which weren't purchased until a month later, as I see my graphs are dated April 22, 2000....
I don't know how to plot curves in this space, nor how how to post and refer, so I'll just list calculated DIFFERENCE data between two pairs of test runs. The first string lists the differences in dB when going from the Audio Refinement Complete Integrated to the AVATAR, adjusted for equal pinks, rounded to nearest easy fraction (when read visually), and then to nearest typable decimal for your reading....The second string of data is similar, except showing a second test run REPEATING the AVATAR again, but with an NAD 7400 amp in comparison. The index is frequency.
If you plot the two curves, you will see quite remarkable agreement....If you then take the "difference of the differences" data to evaluate method imprecision among other
info note the otherwise randomness and smallness of the noise (indicating the relatively high confidence level of
my conclusions), and perhaps the wildness shown in the top octave. However, looking back at my raw data, I see that the original SPL levels of ALL data entry pairs for both test runs for the ARC and the NAD amps were within +/-1dB across the whole band! So it's clear that the variability is due to some inherent behavior of the Avatar....
Once you plot the curves (a picture's worth a thousand words here, guys 'n gals, so PLEASE...), you'll notice an interesting old "west coast" u-shaped curve, with a pronounced, wide dip starting at 100Hz, bottoming at 250Hz, and then starting a long climb back to reference at about 2kHz. The bigger problem is that this climb continues into a sharp spike at 4-5kHz, then tumbling fiercely into the ravine -15dB down at 12k! That it wildly rebounds past unity at 20kHz is also of interest....That this behavior was repeated in a separate test when compared to another amplifier later is of course important. (If the acoustic results were simply a u-shaped curve then of course one could just increase the gain a bit to bring the mids up, and thus enjoy a plumper bottom and bright top, referring to the amp as one with a warm bottom, recessed mids and a bright top. But the trampolining between 1k and up belies categorization nor acceptablility.)
I also ran several additional sweeps more casually, noting that other than a gain difference of 1.16dB, the triode and ultralinear modes acted similarly. It should also be noted that I did NOT plot response below 40Hz, as it was not of interest, and the Fidelios were set up too far out into the room to have sufficient boundary support to have adequate output below 50Hz........................................................Freq:ARC to VAC diff/NAD to VAC diff: 50Hz:-1dB/-1dB 63:-1/0 80:-0.67/0 100:-1.67/-1.33 125:-2/-2.33 160:-2.33/-2.67 200:-2/-2.33 250:-2.67/-3.33 315:-1.33/-2.5 400:-2.25/-1.67 500:-1.5/-2.5 630:-2/-2 800:-1.25/-1.5 1k:-1/-1.25 1.25k:-0.5/-0.5 1.6k:0/-0.25 2k:+1/0 2.5k:+1.25/+0.5 3.15k:+1.5/+1.25 4k:+2.67/3 5k:+3.25/2.33 6.3k:+1.25/+1 8k:-2.67/-4.67 10k:-7.67/-10 12.5k:-10.33/-12 16k:-5.33/-3 20k: +6.33/+2.67 (Phew!)
Difference data: test 1 minus test 2:
0 -1 -0.67 -0.33 +0.33 +0.33 +0.33 +0.67 +1.17 +0.6 +1 0 +0.25 +0.25 0 +0.25 1 +0.75 +0.25 -0.33 +0.9 +0.25 +2 +2.67 +1.67 -2.67 +3.67!
Further, the very high Q of the data above 6kHz suggests that a finer source of tests signals (1/6 or 1/10 octave warbles) would have been most beneficial to assess this apparent unruly behavior..............................................................................................................
So what do you think's going on guys? VAC had no additional response after I sent them the actual data and curves three years ago. The responses below 3kHz can almost be lived with in the old pulled-back-mids style, but I've never seen anybody's "simulated performance with a real speaker load" curve look this bad. And yes, BOTH channels driven simultaneously, so I doubt that it wasn't one side oscillating wildly or anything obvious. All tubes glowed equally in pairs, etc. And again, triode = ultralinear except for 1+dB gain. So I'm stuck here, hearing only wonderful things about VAC and its pricipals, but having only experienced the behavior noted above with the one product I spent much time with. Again, they redesigned this Avatar, right?
I think everyone who reads this can draw their own conclusions as to what was actually measured here.
The amplifier's real output is not measurable through a non calibrated loudspeaker, with further room calibrations made, to compensate for room, frequency anomolies.
If this measurement of the "amp" were taken with a million speakers, we would see a million different results.
I thought, when I read this that the, so called, 'amplifier measurements' were suspect, now I, and everyone can see what has happened. Poor Kevin, he must be pulling his hair out.
Good listening,
The ARC and NAD were shown to have only +/- 1dB across the whole band? PUULEASE.....this whole set of test measurements is just plain FLAWED. I say you stick to just listening to your system. ; )
Well, it's clear that Lrsky and Balekan don't understand the test. Once again, a reference test was devised using the same software (CD of 1/3 octave warble tones), CDP, cables, speaker/positioning/room, microphone/meter/battery/tripod/positioning/decade-selection, and operator eyes, with the ONLY VARIABLE being the choice of amplifier. Three ss amps and one VAC AVATAR were tested. The three ss amps agreed with each other so closely in ALL results that it is easily said that they grouped as a "standard" curve. The VAC AVATAR's responses were extraordinarily different. I posted the results of two of the test runs in a previous post above, noting only the DIFFERENCE DATA from the ss amp to the AVATAR in each of the two test runs.
LRSKY, Everyone CANNOT "draw there own conclusions as to actually what was measured here"! What were measured were in-room responses of total systems, identical except for the substitutions of amplifiers. The difference-data was then plotted as a curve. It should appear as a straight line of zero slope, as it does between any two of the ss amps. When any of the ss amps is compared with the AVATAR the difference surve is as provided above. What the original data curves are doesn't matter, and of course WOULD differ dramatically would a change in ANY item in the reference system chain...especially a transducer (speaker or the test microphone) and/or its positioning. That's why I took GREAT pains to assure matched tested conditions for each pair of sessions. (Even test meter battery strength was assured). So now you understand that NO claims of linearity can be made for ANY amp in this test, as there is no absolute reference for linearity. Granted. Of course. I don't care. Nobody does. My only attemt was to validate what I heard empirically: the VAC significantly changed the sound of the Verity Audio speakers, and much for the worse (IMO), compared to other amps I had on hand. I wanted to see if I could bear this out spectrally, and indeed the results are all too obvious.
So Larry, I trust you understand that I wasn't attempting to measure amplifier output on an absolute basis. It's unnecessary in this case. Differential testing is much easier and at least equally valid, as common biases are eliminated. My background is in test methodology, so give me a nod here....
Balekan, you too misunderstand. The ss amps agree with EACH OTHER within a dB across the band, not with any other reference axis. Again, the actual curves plotted are pretty wild messes that combine the speakers in-room with the pretty serious errors of the SPL meter. But I've gotten good enough at REPLICATING test runs with this setup to be able to tweak crossover designs in 1/3dB increments in the past, so it's been a pretty subtle differential tool.
As others who use similar setups know head-movements account for the greatest amount of the imprecision of the noise-floor. The ss amps all agreed well within +/- 1dB of EACH OTHER as a group, which allows a conclusion ofan "ss standard" for this test, if you will. The two VAC curves agreed quite well with each other, also (I didn't test p level, as it's only two sets of data), and the differences between this data and the ss "standard" is so large as to be very significant, and remarkably audible.
Again, if you plot out this "difference" curve as provided above (either one...they look the same), you can get a sense of the acoustic analogue (no pun).
L&B, I'm trying to think of a good example to explain to you the differential testing method I used. If you and your buddy are having a race it's unnecessary to know far or how fast both of you have run to know who's ahead; you just have to measure the distance between you.
This setup has been used innumerable times by speakerbuilders, especially, to tweak their designs. Again, there's almost no interest in the ACTUAL reference level against 0dB, but only in what happens when you tweak a cap or resistor on that tweeter, for example. You rerun the curve, and look for a subtle shift in the results, and plot the difference data. Same thing applies for testing amps...especially those with high enough output impedences that could actually change speaker output spectrally. Again, the amplitude of the distortion here is what is so shocking, and I imagine said non-linearity was probably one of the reasons for the redesign of this amp. I didn't mean for this chapter to ambush the thread, but it's clear that
L & B didn't understand the test methodology nor the validity of the results. Thanks.
I think they are beautifull to look at. I love the fact that by all accounts they have excellent customer service. Unfortunately, in my experience they sounded like the models of everything that's reputed to be wrong with tubes. To each his own, and definetly not for me.
It is impossible to measure amplifier output as a 'qualitative' or linearity value, "through" loudspeakers.
I know your attempt may have been sincere, but it serves no point ultimately.
The speakers, as an electro mechanical device invalidate the test, with their own unique set of impedence and back emf.
If you want a real test, of the amplifiers output, in what may be considered broad based in nature, you would have to measure 100 pairs of all types of speakers, and then, you would have 'something', but I am not sure what. Also, you would need to room calibrate the mic's. This is too much to go into in a small thread.
Call ANY manufacturer of amps and pose this question to them. Cite your techniques and get their feedback.
Please don't take my word for it.
Lrsky, one could make that argument for any component. All we can offer is our impressions based upon our experiences.
To reiterate, ask any manufacturer about the validity of this experiment. I am sure it was done with good intentions, but it is flawed, not because I personally think so. Call ANY electronics manufacturer and ask. PLEASE DO NOT TAKE MY INPUT SERIOUSLY. I am just one of the guys.
Ask Dave Gordon at ARC, Bill Conrad of conrad johnson, Dan D'Agistino of Krell, Jeff Rowland. Need I go on?
If it was important enough for Subaru to go to all that time and trouble to do this in the first place, surely he won't mind getting input from the actual manufacturers of the gear, who try so desparately to create these products, why this form of testing is invalid.
They WILL be forthcoming if you just ask.
Lrsky, we're way past your suggestion. MANY manufacturers of audio components devise simplified controlled test methodologies to evaluate product tweaks and of course during ongoing manufacturing QC. You don't have to reinvent the wheel every time you want to look at a performance criterion. I spent a former professional life devising test methodology for laboratory equipment evaluation and manufacturing processes, culminating in chairing ASTM/ANSI and ISO subcommittees in the late 80s. The subsets centered around piston-operated volumetric-ware: not unlike tiny "tweeters" for liquids, currently used in all labs tosample, measure and move around small (1 uL - 1ml) aliquots of liquids hither and yon. You see these little pipettors (The "Pipetman" is the one I co-invented) on TV as reportes think they're camera-friendly for the general public....
The point is that there is NO DIRECT WAY to measure a uL of volume in a short amount of time! You have to rely on an indirect means, perhaps such as radiometrics, spectrophotometry, or im my developed expertise, gravimetry of water. By knowing a LOT about what happens when you move volumetrically and then weigh tiny amounts of water drops you can very noiselessly measure true volume. That's how nearly ALL the volumetric lab equipment in everly lab in the world was calibrated. And I wrote the friggin methodology. Now doing the ALL the reference measurements for imprecision and bias (barometric pressure, temperature, evaporative blanking, time-clock matching, microgram balance calibrating, operator bias calibrating (these are often hand-held devices), and a few I've plumb forgotten, for EACH string of measurements would be preposterously inefficient. Especially for $100-500 hand-tools. So manufacturers have devise highly-controlled procedures (or at least that's what my publications were supposed to teach them to do!) to shorten these "controls" to only several minutes per device. It was this kind of atmosphere in the late 80s in Geneva that spawned ISO9000/1/2etc. Unfortunately that's become more of a paper-cover set of machinatuions rather than necessarily a raising of quality level. But I digress.
It onlly takes a cursory reading of a few back issues of Speaker Builder et al to uncover manufacturers who've used simple SPL meters in real-world acoustic setups to uncover non-linearities in switched-component analyses via differential testing. I casually mentioned my testing to a chief designer (ex-KEF, now Boston Audio), as well an ex- BBN master acoustician, who implicitly trusted the soundness of matched-reference technique analysis for uncovering non-linearity of a suspected "unorthodox behavior of a gain device". Indeed, when I mentioned my results to VAC's folks, after a cursory description of technique, their concern was NOT my procedure, or its validity, but the degree of nonlinearity of the results, which they said again seemed surprising, even for the admittedly unruly output stage of the AVATAR.
So Lrsky, I kindly suggest that you step back a bit here, as my technical prowess as organizing a valid scientific inquiry is not truly in question...I've got the backing to pass ANY scrutiny of methodology despite not having conventional DIRECT high performance traditional electrical instrumentation, and please not be coy about summoning the industry gods to pass judgement on what anyone of reasonable facility with the scientific method can discern is a well-run set of differential tests. As well, the amplitude of the non-linearity difference to noise ratio is VERY high (although not calculated), so my experience tells me I'm on solid ground with the stat calcs too.
But again, rather than pee back at you, I'd rather educate.
What you simply do NOT understand is that calibrated speakers, room, mic, cable, etc., are NOT needed to run this type of test, as these items are held STABLE through all test runs. Repeat runs (controls) proved that system imprecision was extremely small (which I think you may not have a problem with); indeed the raw data is NOT flat in dB across the 27 or so test frequency points for any situation, because of ANY and ALL of the effects of the system. But they are STABLE as a rock (well within 0.5dB).
Again, the biggest sources of imprecicion are human headmovements and parallax error in eyesight.
This test can, and has been used validly by INNUMERABLE MANUFACTURERS to assess changes in one variable at a time at ANY component position in the system chain. I think that's part of what you don't get.... Whereas there is NO VALIDITY in quoting actual raw data in dB vs frequency because of no pure reference scale calibrations (that and efficiency are the reasons why I didn't post it); because of the stable RELATIVE REFERENCE, there can be great validity in concluding statistical significance from differential calculation of this "humpy data".
Part II (Sorry!)
I guess another part of this is that manufacturers generally use resistive loads for amplifier measurement, wherein linearity usually appears reasonably flat. We're now used to seeing a curve now and again from some testers (like Atkinson at Stereophile) who throw in a "projected behaviour with an 8-ohm real speaker" curve, which, especially with a high output impedence amplifier, will show some non-linear frequency dependent behaviour.
In a way, there's some useful "single-blindness" in having very raw data. Indeed, after running the first SS1 vs VAC test, one can't tell by looking at the raw data anything.
I then ran the second test: SS2 vs VAC. A cursory examination of the two sets showed that SS1 very nearly equalled SS2, and that VAC very nearly equalled VAC. I then tried SS3 by itself, which equalled the two SS. The amplitude of difference between the VAC and the three SS was quite large (see the curves again), and correlated nicely with the gross differences in sound differences. Certainly the three SS amps had differences in sound, but these had to do with grittiness, edginess, decay, dimensionality, and all that typical SS stuff. The Audio refinement Complete Integrated clearly sounded the best. The Acurus and NAD I didn't like much. But ALL THREE SS AMPS sounded TIMBRALLY EQUAL, and indeed measured spectrally the same. It all makes sense. (Now do you understand, Balekan?) The three SS curves are very tight (intertest imprecision mainly given only by pink noise bias difference set by gain control). The two VAC curves are quite tight, only being a bit at variance at the 16k and 20k points where both are at highest slope, and therefore coarsest measurement...but also greatest non-linearity--quite wild rides....
The only almost-sily fly in the soup here is that someone could actually postulate that since the raw data is relative to an unknown (yet stable) reference base, isn't it possible that it's the VAC that is linear, and that the THREE SS AMPS are all wrong? Yup. Entirely possible. And if there was only one SS amp I'd have to agree, and would never have published these results. But when THREE different SS amps agree so highly, and one TUBE amp disagrees so greatly, TWICE, and sounds horrible, to boot, my money's on something terribly wrong with that output stage...when mated with the supposedly benign Fidelios. Ern
"...and please not be coy about summoning the industry gods to pass judgement on what anyone of reasonable facility with the scientific method can discern is a well-run set of differential tests..."
Why would you refer to industry "experts", as "Gods" in such a sarcastic manner? What ax are you grinding, and why?
My comments were aimed at the potential of some possible unusual load of the the speaker, and possibly room effects to skew any results, and that if you used a host of speakers, that the test results would be different with each differing reactive, rather than resistive load.
There are numerous questions, but a few come to mind. Did you use calibrated mic's? Have you previously plotted the room for additive frequency anomolies, or did you do as most real qualified scientists do, and use an anechoic chamber, or a faux chamber, designed with the flaws input into the response curve of the room,in order to factor those errors out? Again, I would ask if you use more than one set of speakers, if so were the results of the amps exactly the same?
No one is peeing here, I simply said I thought you did the tests with sincerity, but that I doubted the validity because the reaction of only one set of speakers, with one Avatar amp, and no pre test,test data on it, to compare with others of its ilk,(meaning, was the amp tested, and confirmed to be in perfect, or its intended operating condition and certified to be so?).
Speakers present reactive not resistive loads, as everyone knows, hence, tests of an amplifiers output, is done with various resistors, (still flawed) yes but equally so, since this test is still into resistors, even though of varying values.
Cable capacitance, inductance, any of that factored in, or would you say that this doesn't make any difference whatsoever in your tests?
Why are you buying such flawed gear? If you have doubts about a product and its output, why not try before you buy; why lie in the bushes (metaphorically) and ambush any manufacturer with such (imperfect, incomplete) testing. Even though I have written many press releases that were released nationally, that does not make me Ernest Hemingway.
And just so you'll know, even though the folks at VAC didn't really call you to task on this test, I know personally, that a coffee mug was offered as a prize to anyone who could explain your tests, and how they relate to real world.
The implication of your test is that the Avatar is flawed in its output, and that Solid State amps are not. I don't believe that, as a narrow finding, that this is correct. I don't know, and neither does anyone reading this, that the Avatar in question was working correctly when you "tested" it.
Also, a little presumptious to think you can educate someone you don't know, and even offensive based on this writing you give as support for that claim.
If only Kevin Hayes weren't so concerned about public image he would join this discussion and "enlighten" you, as to the variables which are not dealt with or even mentioned in your diatribe.
Again, I am only one person. Ask any (and they aren't God's that is insulting) industry expert how valid these tests are, don't ask or try to convince me.
By the way, what audio products have you designed? How well do they sell? With your obvious tallent you should teach all these manufacturers the error of their ways. You seem to be a disgruntled, anti audio person, on some not so obvious quest to discredit VAC. If that is the case, I suggest you move on, sell it and forget it. If not, please be more respectful.
Have owned Renaissance 140 mono blocs from VAC.Still sounding great and reliable after 10 years of hard work driving my WATT speakers.WILL NEVER SELL THESE AMPS!VAC stuffs are expensive but WILL SATISFY YOU. Khai.
Oh ya my sentiments exactly.....I have had many pieces from VAC over the last 15 years, the most recent and current is the 70/70 III amplifier. There is no question that VAC absolutely makes some of the most musical gear available for the dollar-regardless of price. And their design and craftmanship are second to none IMO. And just as important to me when buying expensive high-end gear is the commitment of the manufacture to support his/her product and I can tell you from my own experience that the customer service at VAC has always been nothing less than stellar! Kevin and his team has always, and continues to, make every effort and sacrifice to support his product and make his customers happy. In my opinion VAC exemplifies all that is great in this fun hobby.
Lrsky, you still don't get it! I have absolutely no axe to grind, DON'T OWN the bloody amp, and will try to answer your queries in order, as I flip back and forth: I used the terms "gods" because the suggestion that CEO's be called in to assess a simple differential test is technically naive. Any of the mentioned companies techs well-grounded in the scientific method would pass on the test without mention. Seriously. You simply do not see this. Secondly, the Verity Audio fidelio poses no unusual load whatsoever, being of fairly flat impedence with a 5.7ohm min, I think. But OF COURSE it's expected that the results would be different with a change in speaker IF the output impedence of the test amp was high. That's precusely the test's hypothesis! Why the bugaboo that the results simply prove convincingly that to be true? Again, changes in LOAD, and room loading, areinconsequential, as they are FIXED across all trials. Again, the basis for a differential series of test runs: only one variable (the amp) changes. Please try hard to understand the reasoning behind this. No condescension meant. It's critically important....Only one mic was used, so it's calibration is not of concern. Do you understand why? If not, I can explain later. Again, as the room anomolies remain FIXED, their effects are NOT of concern. Your dig was not necessary. I've TAUGHT more real scientists than you can count. No, I did NOT use more than one set of speakers (one per channel), because the point was NOT to investigate HOW the VAC varies with speaker load changes, which is another experiment requiring different test equipment. My test procedure was only to determine what the DIFFERENCE in frequency response was between the VAC AVATAR and the two SS amps I had on hand, as empirical audible evidence indicated a great discrepancy....No, I did NOT in any other way test the VAC beforehand, as it was a dealer demo, and naively trusted to perform normally. Both output halves matched, which seemed a rudimentary qualification, as well. It's not a customer's job to perform manufacturer's final QA. Yes, I'd rule out the 8' Nordost Red Dawn cables' very low inductance and resistance as significant contributants here. But that suggestion simply muddies the waters again! All system componentry (test equipment and conditions) were listed, unvaried, and NOT unusual in any way such as to skew freq resp between ss and valve amps, as most will agree....Again, I didn't "buy such flawed equipment", and thus didn't "lie in the bushes to ambush" anybody. I simply doubted what a gushing salesman who sold me Verity Audios told me about the Avatar, as my ears heard differently, so I tested it against two other amps in a very simle, but VERY VALID manner, and produced extremely significant results. Certainly NO-ONE has countered the methodology to date. A full list of the raw data is available to VAC as well anyone, although I doubt that anyone cares at this point, 4 yrs and a redesign of the amp later!...Again, why is my testing incomplete and imperfect, Lrsky? I remember back in the mid 80s I sat as the US rep on a Technical Advisory Group at ISO Tech Com 42 (Lab Equip) in Frankfort, where the DIN Secretariat lauded us for writing a standard that was efficient and tight, containing only what was "sufficient, but necessary". It was important him, as he had to organize translation into 17 languages for balloting. If I had tried to reinvent the wheel with every procedure we proposed in an ISO method we would never have gotten anything done! So sir, you may or may not be another Hemingway, but when it comes to running a simple differential test, please just trust that I know what the hell I'm doing. And I'm quite sure that a coffee mug can look like a red herring from certain clever angles, and necessarily so, as it's easier to shoot the messenger and leave the waters muddy, as you've done....
However, it IS true that NO ONE knows if the suspect AVATAR was working correctly when tested. I do remember that it sounded the same in BOTH channels, in both triode and pentode mode. So I continued like an ordinary consumer, trusting that it was a normally-functioning unit. It had ample output, too....
Lrsky, your last condescending remarks are is absurd, and perhaps psychological projection? I need ask no one if my testing methodology is valid. Chrissake, just take any college-level lab course and learn how to perform a one-variable test procedure. It's not alchemy! I've designed a couple of two-ways, and a three-way in the early 90s, using the same test setups to carefully tweak crossovers in 1/3 dB increments over 1 octave bands, thereafter learning you can't get a manufacturer to supply you with driver pairs matched well enough, and I didn'rt want to get into computer-matched pairs. I have GREAT respect for Verity, Snell, even Boston, et al, who control driver spec closely enough to make nice clones. I learned this from many years controlling production and QA of the world's most popular laboratory volumetric measurement equipment, called the Gilson "Pipetman". It's a handheld small volume auto-pipettor used down to 1 uL, calibrated by differential test methodology I developped in the 70s using gravimetry at the
1ug sens level. It's this stuff that I honed into ASTM and ISO standard procedures for calibrating volumetric ware so users in labs worldwide could test their pipettors, dilutors and dispensors inhouse efficiently instead of having to buy new ones, or, as you would prefer, Larsky, measure the room, all the beakers, and maybe the drapes too, and perhaps ask for permission before seeing if it's ok! Sigh...why the doubting Thomas?
Of late my semi-retirement and slipped disc has me still enjoying life in a third career as Boston's SubaruGuru, and as a contributor to this community, supplier of nifty $39 DIY all-Teflon PCKits that keep me in touch with a couple hundred of you guys....
Disgruntled? Hardly. Anti-audio? I've 50-60 cheap CD's I scooped up in Italy and at Heathrow this August I haven't even goten to yet. My two-ch ref system and my Steinway B are the aural delights of my life (plus frequent visits to Jordan and Symphony Halls). ANTI-audio? You been writing too much commercial copy? Re VAC, I have nothing but respect for a small successful company that manufactures great products. I've been self-employed for 20+ years. I have several friends whose small basement ops are now $5-8M music/audio companies, and believe me their noses are to the grindstone. I also just sold a Subie to the wife of the ex-production manager of one of them who, after 15 yrs, got sick of rushing product out the door to meet trade-show dates, brushing aside QA warnings. I wore BOTH those hats in the 70s and 80s at the same time, here in Boston AND in France; I know the stresses implicit when you've promised you'll never ship a product until it's perfect, and then you release a first batch, and then a second level tech finds a flaw two days later....
So yeah, it's easy to say that I got a bad AVATAR, or to incorrectly convince the naive that because I didn't calibrate a mic or measure the drapes my test is flawed, but that's all bull, and the congnoscenti know that. No axe to grind. I'm not into high output impedence tube amps. I tried ONE, May 2000. It went crazy on the VA Fidelio...sounded horrible. Freq resp was crap, as THREE SS amps self-agreed as a group. Here are the numbers: nice and valid. AVATAR since redesigned. Fine. Everybody's happy. 'Cept Lrsky. Why?
I have owned vac renaissance 70/70,s for over 4 years,it is a solid reliable great sounding piece of equipment,currently driving quad 989,s to good effect.A friend bought some class a/b more powerfull mono blocks and suffered a few minor glitches.Kevin Hayes handling of the situation marks him as a gentleman and person to be trusted.Great product designed and built by an honorable company,pick the correct model for the job and relax.

Just wanted to raise a couple points about the above discussion. I don't believe the standard Avatar has been redesigned, although VAC may have made some minor changes since its introduction several yrs ago. VAC has come out with an Avatar Super, which I believe retails for $6000 versus the standard Avatar's $4000 price. The Super is a complete redesign, using diff. tubes and circuits, so the standard Avatar cannot be upgraded to a Super. And, yes I am a satisfied standard Avatar owner.

I have no technical knowledge with which to comment on the disagreement expressed above. However, with one exception noted below, I've never had any major problems with my Avatar, while using w/ Spendor S3/5s and 2/3s, Reference 3A de Capos and now Living Voice Auditoriums. I have listened in the shop to several SS amps versus the Avatar, including Creek, Roksan, Sim and Marsh, and never felt the Avatar deficient compared with them. However, I will mention one potential short-coming. When I had the de Capos, even though they were a fairly efficient speaker I found that in triode (27 W) they often simply didn't have enough power with large-scale classical & rock music to produce the low frequencies with sufficient authority, and that I had to switch to ultralinear (60W). This was never a problem with jazz, blues, etc., and my LV speakers, while they have better LF response than the de Capos, are also more efficient so it is less of a problem. However, my experience suggests that the Avatar esp in triode simply may not have enough power to drive a "full-range" speaker of average or even above average efficiency, in a larger room, esp. with large-scale music. I can understand that some people would view this as a serious flaw in a $4000 amp. However, I believe the Avatar, when used in a moderately sized room, with fairly efficient and "tube friendly" speakers, and with good supporting equipment, is a very neutral sounding amp, and delivers some of the best reproduced music i've heard, esp. jazz/blues/"classic" rock, etc. Just my two cents.

TH, again perhaps the unit I borrowed was somehow seriously defective. FYI, output difference between triode abd ultralinear was +1.2 dB pink. That may or may not be a hint to VAC of whether this unit's performance was outlying the norms back in May 2000. Wish I had recorded the Serial No. for their attention.... The dealer (Ensemble in Arlington, MA) went belly-up in '02 as well, so tracing it seems difficult. Believe me, there was NOTHING neutral about this unit back in 2000. Glad you're happy. And if the Avatar is such a good circuit that it merited serious attention to upgrading with the result that VAC expects the market to laud it at $6k, then I trust that they know what they're doing, and hope that I simply happened to get a bum one.
But please, don't shoot the messenger nor his methodology.
Almost every biochem, analytical chem, microbio, virology, epidemiology, etc. lab in the country uses volumetric ware calibrated by "short-cut" procedures I honed and published in the 70's and 80's (that and a buck get's me HALF a cuppa...); so if you trust that your blood test comes back with some semblance of accuracy, or the cancer research at least seems to hold SOME sense of statistical promise for your mom's lump, please give me a bit of credit for somewhat creatively differentiating lousy performance in a specific horribly non-linear amp. Sorry for the wax job.