On Saturday I had the pleasure of again hearing Ack's system. He has restored the resistor values for the speakers to the greater treble extension that I heard the time before last, added MIT Oracle pigtails (see post #896) and worked some more on the crossover for the woofer (I think).
We compared the Schiit Yggdrasil Analog 2 DAC (Yggy2) that Ack had on loan from me for auditioning -- while I had been away on vacation -- with Ack's modified Berkeley Alpha DAC. Ack has already left some impressions on my system thread about the Yggy2, and now I could hear for myself why Ack is so enthusiastic that he bought one. I know that Ack's modified Berkeley DAC is considerably better than the stock unit that I had in my system as well (for example, the modified Berkeley does not congest on fortissimo massed strings as the stock unit does). Nonetheless, the Yggy2 was better in every way, and the differences were not even subtle.
One very obvious thing was that the Yggy2 has better rhythm; it is as good a rhythmic performer as I have heard, analog or digital. The differences with the Berkeley DAC were even greater than I had thought from remembering them in my system. Ack always thought my system had great rhythm, but his system with the Yggy2 in it also performed extraordinarily well. One thing that I noticed during the whole session was that the subwoofer was never in the way, unlike before; I suppose this may have to do with his latest crossover adjustments for the woofer in his modified Martin Logan speakers.
The Yggy2 also excelled in sheer speed. It was always incredibly precise and clean, from treble to bass. I would never have associated the sound of the Berkeley with being "woolly", but in comparison it was, at least on some recordings. While I know from my own system that the Yggy2 has great speed, that speed was put under a magnifying glass in Ack's system.
The extreme treble register on piano was already impressive on Ack's electrostats with the Berkeley DAC, but the Yggy2 showed even more speed and purity. I have never heard such cleanness in the extreme treble of piano from a conventional speaker; nothing beats an electrostat where basically the entire membrane is a 'tweeter', and thus does not distort even with quick, strong attacks in the treble, which are portrayed also in a dynamically convincing way on Ack's modified Martin Logans, held in tight grip by the Spectral amps. The piano sound on a great recording of Busoni's fascinating piano concerto (Gerstein on piano, with Boston Symphony) was chiseled out with extreme precision, and also reflected the somewhat metallic character of a Steinway Grand Piano with open lid; the Berkeley DAC did not manage to do that, and in comparison sounded indeed a bit woolly on the piano. On other recordings the Yggy also correctly revealed the comparatively non-metallic sound of smaller pianos with apparently closed lid as accompaniment of, for example, solo violin. The Berkeley DAC just did not make the distinction. The Yggy2 also portrayed the orchestral sound with a more convincing body and precision than the Berkeley did. What sounded like a fantastic recording with the Yggy2 seemed a merely good one with the Berkeley.
As for timbral correctness, I brought another acid test with me, an extraordinarily well recorded CD with solo flute works by Stockhausen. I had noticed a large difference in timbre of flute between the DACs in my system. Flute sounds relatively light and very 'refreshing' on the Berkeley DAC, with apparently more timbral inflections. In comparison the Yggdrasil DAC portrays flute with a warmer, darker and more even tone. At first I was shocked about the difference, but more live experiences convinced me that the timbral portrayal of flute is correct on the Yggy2, rather than on the Berkeley DAC; most recently I heard in a concert that I attended with WBF members Peter A. and Madfloyd that warm, rather dark flute tone in Mozart's concerto for flute, harp and orchestra. While Ack's modifications have improved the Berkeley Alpha DAC, we heard in his system that the innate differences on flute remained the same, with the Berkeley still having that 'refreshing' yet slightly artificial tone. This may be one of the rather obvious timbral differences why Mike Moffat, the designer of the Yggy2, says that he does not like the nowadays common delta sigma conversion (as in the Berkeley DAC) and instead prefers 'old-fashioned' ladder DACs, as the Yggy2 is one. Schiit sells lots of delta sigma DACs because they can be made much cheaper (all their $ 100 DACs are delta sigma), but when Moffat gets serious about design he makes ladder DACs.
There is also an incredible dynamic speed. Some passages on track 16 of the Proteus 7 brass ensemble CD "For Your Ears Only" (at 3'10", 4'14" and again half a minute later) feature very quick exchanges between trombones and trumpets, and the fast dynamic surges, even explosions, in those passages were absolutely incredible with the Yggy2 in the system. On the Berkeley DAC those passages fell flat dynamically, it was not even a contest. Those dynamic explosions with the Yggy2 in the system came closest yet of reminding me of a real brass band -- and that on electrostats (!) which are not typically known for their dynamic prowess. Yet typically they are not driven by such source and amplification. Hearing is believing, is all I can say.
While my system is very dynamic, and has been experienced as such by every visitor so far, it does not project the brutal dynamics in those passages as Ack's system does, with of course also the Yggy2 as source. The recording is not quite as in your face on my system and also sounds slightly darker, which of course can have an influence on dynamic perception. Yet it may well be that the intrinsic dynamic capabilities of my system are not quite the same, even though in other passages of that recording I hear terrific dynamics at home. Regardless, the fact that the dynamics in Ack's system are so explosive is enormously impressive and also an astounding testament to the capabilities of the Spectral amplification. The system shows the contrast in dynamic speed between the two DACs in a most incisive manner. I would assume that the amazing dynamic speed of the Yggy2 would make it a great source in a competent horn system.
All in all, the sheer speed of the Yggy2 is a great match for the speed of the Spectral preamp and amps. Ack's system, which sounded the best I have heard it, shows once more in its own way just how good the Yggy2 DAC really is.
Even among all this impressive sound from the system, we heard a real-life reality check. Ack's son Constantin played for us a bit on his tenor saxophone, and the sheer bluntness and presence of sound, as well as the enormous power and body in the low notes, combined with brutal dynamics throughout the range, puts anything to shame that we have heard from a stereo system. Constantin plays with an enormous fluidity of rhythm and phrasing, a true natural talent!