How do Digital Amps Mfrs. compare in sound?

Guidocorona, you're a piece of work. You hear angels don't you? I know the "Consciously Guided" when I hear it. I'm going to start calling you "YODA of HIFI." ;)

hmmm, me thinks last time I heard 'em voices I was 16. . . right in the middle of the Sturm und Drang of adolescence. . . now I'm only a crotchety old prankster foolin' 'round with words and audio components.

Hi Coffeey, small design improvements can make large changes in sound quality in any design. Class D amps have always been good, maybe not great but good. UCD in the last year and a half has redesigned their boards and have chosen some better components. Class D amps use allot of surface mount parts and that is the reason most companies buy modules from B&O (ICE) or Hypex (UCD) and then design and build their own power supply. Now that class D production has picked up, many surface mount component manufacturers are willing to set aside the better parts for these designs. Most, if not all of the sound differences between tube and solid state amps are the parts and power supply. The same applies to Class D. Circuit topology for tube and solid state haven't changed much in decades. So how is it possible for a manufacturer of these amps to make their product sound better then last years or even 10 years ago? Parts, board layout, isolation and power supply.

Excellent points Stereo. I would like to add that at least 2 manufacturers (Bel Canto and JRDG) have started to add pre power supply current rectification in some models. This means that the power supply is essentially fed DC from a current reservoir of capacitors. The idea is the DC current is expected to:

1. largely eliminate 2 way AC line noise in and out of the amp.
2. Keep internal capacitors more optimally charged.
3. Be able to draw power for large transient from the DC reservoire regardless of the current state of AC 50/60 Hz phase.
4. Increase overall power conversion efficiency.

Some of these amps do sound amazingly musical to my ears. . . if and when more devices adopt various form of rectification prior to power supply, we may eventually be able to determine if there truly exists a correlation between input current rectification and sound quality.

I probably won't be adding much to the discussion by simply suggesting (as another poster did) that it depends on the manufacturer. For the past 2 weeks I've been listening to an ARC 150.2 which I swapped into my system in place of a tubed ARC D90B. The 150.2 is a tripath class T amp, which is really just another name for class D. I'm feeding it with a tubed ARC SP-8, and it sounds as good as, if not better than, the tubed amp it replaced. I also have the TAS issue which compared a number of class D amps, and if you read the review of the ARC 300.2 (the bigger brother of my amp) you see two opposite opinions - the assigned reviewer loved it (as I understand, he actually bought one after reviewing it) but Jonathan Valin, another TAS reviewer, definitely didn't like it. It seems to me that when you have two professional reviewers for the same publication disagreeing, it certainly points up that there is no "easy answer" to the question of class D sound.