Thursday, June 18, 2015

The Yggdrasil

I'm pleasantly surprised to see a new PCM DAC on the market from Schiit.  At $2299, this is much less expensive than the least expensive PCM DAC from MSB, and there aren't many others being made now.  And it sounds very sophisticated, perhaps more sophisticated than any preceding PCM DAC in many ways.  I'm somewhat interested.

Though I need to have at least 6 DAC's in my home (4 in the living room system, 2 for the bedroom system) as standalone DAC, not counting the endless DAC chips in other equipment (ONLY the living room and master bedroom systems are High End enough to warrant actual DACs…if any do…).  So I'm not sure if I'm going to spring for $2299 for any of them.  If I get one $2299 DAC for the living room, I'd automatically have to get two, so both amplifiers under A/B testing would have the same kind of DAC.

Here's a discussion at ComputerAudiophile.  Here's an endless rambling discussion at Head-Fi that generally favors PCM DAC's as compared with Delta Sigma and DSD.

And they say Mike Moffat was working on this for 5 years (along with a mathematician and others).  I only got on the PCM bandwagon last year (though it seems like a dozen years since then).  I see now that he's been on the PCM side of the debate now for a long time.

I met Mike Moffat very briefly in 1979 when I was an audio technician at Audio Directions.  He came by with his Theta Preamplifier, which was demonstrated at one of the first meetings of the San Diego Audio Society which I later became a President of.  He is very charismatic.  The preamp sounded good to us, but the tech staff I was part of felt it was sloppily built.  Well that was a long time ago when Mike didn't really have a company yet.  I could hardly have imagined what he would be up to in the future--a towering and pioneering figure in the history of high end DACs, though he has not been without many critics including some who might well call the whole field a fraud.   Hypester or Genius?  Honestly I could never tell, though I did lean toward believing he was more on the hypester side.  But maybe I was wrong then, or maybe I've become one too.  Anyway, I'm glad to see he put his Jobs-like force to make something I now find interesting.  Moffat seems somewhat like Jobs to me.  Jobs was of course the penultimate hypester, but he had good taste too, chose the right directions, chose the right ingredients, not so much the genius inventor but the genius selector.  I myself use Macs for that reason…though I'd always felt a well configured Gnu/Linux could be better, getting there isn't worth it and I for sure don't have the time.

And I'm pleased to see others thinking about digital technology in a similar way to me.  Though many are still clinging to DSD, in the last year or so (about since I got on board…proof of my overwhelming influence) PCM is back, and more and more designs are recognizing the virtues of real PCM.  I consider DSD a fraud (and have always done so…going back to David Rich's take on it circa 2001 in Stereophile), originally designed to give Sony lots and lots of money by owning the music business and owning the technology.  Well they did get to own those things, as it turned out, perhaps by convincing certain people that DSD was a key, even if it turned out DSD (and SACD) has never been a huge success, it ended up getting Sony the things they thought would buy them endless profits.

I nevertheless consider SACD relevant enough that I have SACD players that get resampled by high end ADC's to 96kHz.  When you're resampling an analog signal, as I do, you can choose any target frequency and it works great.  In fact, I believe strongly that it's better to physically resample in the analog domain generally than to do it digitally, and you might as well sample at the best rate you can support, it's like super-dithered, but it's especially true when converting DSD to PCM.  And DSD can be converted to PCM with little loss--native PCM end to end is a relatively low loss process for a bandwidth limited signal--whereas creating DSD initially causes a huge loss in information in the middle highs up to the inaudible.  I've heard that (not in DBT) but of course I've always been strongly expecting it.  There was only a brief period around the time I got my first SACD player that I had hope for the format.  I didn't bother to even get an SACD player until after I'd gotten a DVD-Audio player, and had gotten frustrated with the Stereo-Unfriendly menuing and lack of titles.

But it seems in the cult world, the status of N.O.S. DAC's is looming larger in the imagination generally than PCM as such (though many combine the two concepts).  IMO a DAC without a proper reconstruction filter is a noise effects processor.

Moffat has never been that kind of fool, all his digital equipment has had considerably thought out digital filters…that's been the hallmark of his products.  So at least he's no fool in that way.  He's focussed on time coherent filters--a concept which makes abundant sense.

How do I know this?  Well of course I don't "know" anything, at least in the sense I could "prove" it.  But I hardly get the bulk of my ideas from listening tests.  Basically all of the times I've attempted to do a double-blind test on something I absolutely believed would be audible, though different from the total objectivist canon, I not just failed, I couldn't even get started.  When confronted with level matched "A" and "B" I found them identical, so the best I could do would be to guess on getting the first impression. Whenever I bothered to go that far, results were close to chance.

But who needs to do such listening tests?  Subjectivists of course!  And I'm basically not a full throttle subjectivist, by any means.  I've experienced myself, strongly, and taken to heart the findings of the DBT testing and attempts at DBT testing I've taken.  Perhaps I haven't taken them to heart the way others do.  But I don't believe proper listening tests actually tell you very much, and are very hard work for what little they do, reliably, tell you.

Better off when possible, then, frequently obtaining and mostly relying on objective test results!

In many cases it's not hard to know what audio circuits do, when they are linear and when they are non-linear.  Of course we want them linear all the time, and in every way, if possible, and if not, we'd like to sacrifice as little nonlinearity as possible.  Do you have a problem with that?  Most subjectivists do!  Even though what I'm describing is not just "a number", it's a concept, it's an objective idea.  They start with hearing what X "sounds like", by performing tests that most likely are producing little more than a random number compared with what one would be getting in a blind test.  I take the blind tests as showing what we actually, and provably, hear.  Everything else is speculation, and in my view speculation about how things work is far more meaningful than performing sighted listening tests.  In fact I fully believe that sighted listening tests are pretty much useless.  They are unreliable and their main product is superstition.

So I want to shove off the idea that I'm just a "measurements guy," though measurements are a fine way to check things out--generally much more reliable, and more interesting, than listening tests.  But better yet is understanding how things actually work.  Did you know that with very high bias (so high basically nobody uses it) MOSFETs can be perfectly linear?  That's what we want!  Too bad nobody does things that way.  It seems everything is compromised.

And it is true that often the most useless things of all have been specifications.  Manufacturers specifications have often been outright lies, or very calculated incomplete truths.  Even at their very best, they have never told the whole story.  The best story of any piece of equipment basically involves a full technical exploration.  The closest to this I know of has been the measurement work by John Atkinson.  I respect him enormously for that.  Meanwhile, I continue to imagine something far better, a far more complete story being told.  And the best story of all includes context.  Fortunately with the web we can get much context quickly, though often we lack the contexts before around 1996.  There is some good old information on Usenet…is that now archived on Google Groups?

Back in April, atomicbob at Head-Fi did a very impressive technical exploration of the Yggdrasil, and he says he plans to check out other DAC's also.  (I had done a lot of technical investigations when I started this blog, and the intent was to do more and publish them here.  My old ones tended to get written down in notebooks that got lost in the pile, and stuff like that.  Sometimes I'd come across a pile of old spectrum analyzer results and find myself amazed that I had ever done something like that.)

So then we can continue making things better, primarily based on understanding how things work, and secondarily by checking them out technically with measurements of various kinds, and ultimately, but very incompletely over any finite amount of listening, with listening tests.  But unless you're going to do the most careful level matching, I wouldn't bother with any A/B testing, just put new thing on and see if it works.

The science tells me I can do that.  I need not bother with the "listen for yourself" mantra of subjectivists (although I do, sometimes, do just that, but hardly ever in a testing context), or anything I consider overpriced, or relatively unimportant.

The science tells me I can do what I want to do.  I need not be shamed by others.

Except possibly by those who say I should be devoting far more attention to the speakers and acoustics than to the electronics.  I do feel somewhat embarrassed I haven't spent more time on the acoustics.

But that's more work.  I like thinking about electronics.  That's what a big part of my hobby is about.

And as I think about how things could be made better, I often like to implement those ideas as well.  It seems to me often that that is what I spend too much time doing.  But there's often no way around it.  If you want to listen to the stereo you got to connect the speakers.

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