Delightful DAC Week :~)

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Please pardon the below shameless product design mugging; I promise that it will clear up closed form math questions. Incorporated in the Yggy and also in the new multibit Gungnir - The Schiit Footlong Mega Combo Burrito Digital Filter:

 

 

It is a digital filter/sample rate converter designed to convert all audio to 352.8 or 396KHz sample rates so that it may drive our DACs. You get it uniquely from us; it is our filter. It took five people many years to design and perfect at the dawn of digital playback, way back in the early eighties. It keeps all original samples; those samples contain frequency and phase information which can be optimized not only in the time domain but in the frequency domain. We do precisely this; the mechanic is we add 7 new optimized samples between the original ones.

 

 

All digital filters multiply the original audio signal by a series of coefficients which are calculated by a digital filter generator. Over the years, before Theta Digital was born (my original company), we developed this filter design/generator. The common digital filter method is a Parks-McClellan algorithm, which has been used in all of the older oversampling chipsets, and persists to this day as the input filter in most ds DACs. Why? I assume it is because it is royalty-free, and the algorithm is widely available as are digital filter software design packages to aid in a cookbook aproach to the design. Now Parks McClellan an open form math solution, which means that the coefficient calculation is a series of approximations which always get halfway there. This of course, means it never completely solves. The worse news is that all original sample are lost, replaced by 8 new approximated ones. Further, the Parks McClellan optimization is based on the frequency domain only – flat frequency response, with the time (read spatial) domain ignored.

 

 

Our filter is based upon closed form math – the coefficients are not approximations, the equations solve; the matrices invert and the math is done. The filter also optimizes the time domain.

 

 

This is the reason that on good recordings (with good playback system as well) through Yggy (and now Gungnir multibit) you can hear the hall, its dimensions, and the exact position of anyone coughing or farting in the room, the motions and locations of instruments being hoisted in preparation of being played, etc. etc. Details such as sheet music pages being turned are not muddled because of clear differential spatial cues. This comes exclusively from our filter. A friend of mine, Jonathan Horwich, sells master tapes in ½ track form – at least 15 IPS, and 30 (I believe) as well. On those analog masters, you can also hear the entire environment before the music starts – what is amazing there is that even if on accounts for hearing “down into” the analog noise, the S/N indicates a 14 bit performance at best for those tapes. 14 bit or not – those tapes, totally scratch my itch. If you want that, we got that and more for your digital pleasure.

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Just to let all know, that I am Co-Founder of Schiit Audio, the designer of all Schiit Digital products and therefore quite partisan.

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My time is limited, trying to get my Schiit together for RMAF, but I cannot resist some quick comments to several of the above posts. Lots of taps permit a much higher slope in the transition band performance, a higher frequency response before the transition band begins (in our case .98 of nyquist), and much more attenuation in the stopband. The filter indeed rings, as all finite impulse response filters do., and it does indeed alias at 700 and something Khz, which is easy to filter in the analog domain without screwing up the sound. There is nothing faith-based about this filter, nor any exemptions from sampling theory. A frequency and time domain optimized filter is NOT mutually exclusive. The key word is optimized; not perfected. The filter has been tested by a non-partisan user here:

 

 

yggdrasil technical measurements

 

 

Those users with good time domain response speakers are well equipped to hear spatial cues should be impressed if imaging is a priority for them. Such cues are far more difficult to hear on headphone systems, but should be audible with the best phones.

 

 

All Schiit specs are very conservative; I have been doing this a very long time since I built and sold the very first D/A converter back in the 1980's. I have built not just for myself but for many other companies dozens of designs, from multibits at the beginning to ds designs and now back to multibits again. (They sound waaaaaaaaay better!) It took several years to reapply all of my original audio technology to modern industrial/defense/medical D/A converters; at Schiit, I am now migrating the technology downwards into all of our upgradable DACs. If you do not believe me, or think I am some carnival barker with a straw hat and a cane selling nebulous sound as euphones or something, then just do not buy my stuff. There is plenty of other stuff out there. One of my favorite sayings is that God could appear to me and tell me how to build the perfect DAC and there are those out there who would accuse me of false claims or numinous science.

 

 

Schiit audio really is a populist audio company. We want to offer the best value products. It therefore has limited products in its line; simplifying the line makes us more efficient. We try to pack in as much as possible at every price point. Understand, we make DACs from $100 to $2300. Generally, our products are compared to products selling for much more. We do not offer multi-colors or D/A converters with volume controls built-in. The Yggy has high enough output to be used with an external attenuator. So get one if that is what you want. We cannot please everyone.

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Gumby does indeed use the megacombo burrito filter, albeit with a few less taps.....

I will not make a multibit D/A without it, as it is what separates us from all other multibits.

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BTW, the Gumby is also true hardway balanced from the digi domain (4 DACs) one per phase per channel.

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As of now, we receive a limited, allocated number of Gen 3 USB engine chips from Cmedia. Because of that, we only offer them for Yggys.

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Back in the early 1970s, before I founded Theta Electronics, the tube audio products company, I had a busy part time biz rebuilding Dynaco Tube Amplifiers. At that time I had converted to the tube based practice for my own system, convinced that tubes sounded better than the solid state gear of that era. In my ramblings, I met John Koval, a man who had designed a modification for the old Qual ESL loudspeakers which made them sound much better. “The mod gets rid of a 5 db bump in the 200-400 Hz region which makes them much flatter” he explained. I told him that I was enchanted with the sound of tube amplifiers and preamplifiers. He explained that as long as the frequency response was the same and the levels were precisely matched, there was no way anyone could tell any amps/preamps apart in blind A/B tests. He had built a custom box that matched levels and randomized any two amplifiers or preamplifiers with a pushbutton to switch between them. Bullschiit, I thought, what about the solid state A/B box and its sonic signature.

 

 

Intrigued, I built a similar box with passive relays and a passive attenuator. Damn, if he wasn't right. It is really difficult to tell differences in an instantaneous blind A/B test between tube gear that I built versus some commercial gear that I was not particularly fond of. I used to bet John beers that I could tell the difference. Usually, I won at 7 out of 10 picks or so – the best I ever did was 9 out of ten. But it was really hard.

 

 

This whole deal made me wonder if I was crazy hearing differences between amps. If what John said was true, and many others have said in the passing 40 years or so, there is no point for an audio hobby involving anything other than transducers. WTF?

 

 

So I tried something new – I still did the blind A/B tests passively, matched levels, but allowed long-term listening to each; at least an hour or two with known recordings. Guess what! Suddenly I knew which was what. I tried it out on John B and Mike and Dave and all my other audio buddies. They called it too – tubes vs a bad solid state preamp. Every friggin' time. My enthusiasm had returned. This taught me that the human ear is an integral, NOT differential device. The audio science police traditionalists no longer dampened my enthusiasm.

 

 

 

So much for the blind A/B instantaneous naysayers. All that matters is frequency response, they say. People can't hear anything much above 20KHz in their prime, less later. The ear has a short memory, it is all bias, blah, blah. They should take up a different hobby, say stamp collecting.

 

 

Thanks to Dr. Heil, the inventor of the Heil AMT speaker who shared this experiment with me over 40 years ago, Consider this: I am 67 years old – my high end extends to just under 15KHz (not bad for and old fart). I can play two pulses 200 microseconds in length separated by 20 microseconds and clearly hear two pulses. Not unusual until one considers that 20 microseconds corresponds to a square wave of 50KHz. And then, there is the time domain – home of spatial cues which audio science measurement traditionalists ignore. I believe that in the quest for the best sound, an open mind is the most important asset. I will even listen to cables, even though I believe in my heart that all technology about cables is well known. Who knows, even an old fart like me could be surprised.

 

 

 

Until then, yet another retelling of my old John Koval saga is 40 year old news to me.

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Post #131 was posted in another forum - it inspired the following comment (name changed)

 

Quote:

 

Originally Posted by DS

"I don't believe it. As far as the two pulses, sometimes one perceives clicks as a result of envelopes and not the underlying tones. Human Echoic Memory limitations are an established scientific fact. We can't accurately compare audio, in detail, beyond a few seconds difference. One can characterize but not differentiate accurately."

 

 

 

I post this neither to be contentious nor to start a pissing contest. Also, I am grateful for DS's support for many of our products and low cost, efficient philosophy. I do not believe in a zero sum universe where if someone is right, then someone else has to be wrong. I also must point out, that despite our differences, I learned much from John Koval (referred in the above post #131) and we became lifelong friends as we concentrated on what we had in common rather than what were our differences. Audio can be a great hobby.

 

 

That said, I do not believe but know from experience that I can tell the difference in long term blind listening between dozens of gain-matched pairs of equivalent products. I also know that I have seen several other audiophiles do the same. In all fairness, I have also seen some who could not. In my theatre directing avocation, I have seen auditionees who had wonderful voices but could not hear tones to stay on key. Those who cannot sing, seldom have singing as a hobby, even though they may attend and enjoy live theatre.

 

I am not a tent revivalist. I do not build products that I place my faith in, but what I know to be better. If I subscribed to the above quote, I would either have to be a hypocrite, or would have sincerely wasted a life and career in seeking and building better sounding audio electronics. I love doing what I do and making it available to others. That notion propounded by DS also invalidates a significant percentage of posts, perhaps the majority, on this forum.

 

 

I love theatre. I love music. I love audio, which is the reproduction on music. All of them are based on soft science. Neither is, for example, medicine. If you give infected individuals an antibiotic, such and such a percentage will get better. If you play Mahler for an audience, such and such a percentage will like the music. If you play our flagship DAC, such and such a percentage will like it. On and on.

 

If you listen to reproduced music, abilities vary widely. All preamps I used to build were RIAA accurate to 0.1db (as is the Mani today - unusual then, unusual now). Some can hear that degree of accuracy, others cannot. Some are tone deaf-others are not. Some can hear time domain (spatial) cues in our Multibit models, others cannot. All I can do is do my best to make my products measure and sound as good as I can.

 

Science today is prone to revision as sophistication and experiments proliferate. Until then, I pledge not to tell anyone in general and DS in particular what they can or can not hear.