Switching amps have come a long way. These amps are from 2004 but were cutting edge at the time. Even though I am still not a fan of switching amps, I can tell you right off that the Audio Physics don't sound "digital".
A friend called the other day: "I am on the road now and have just returned from buying some new stuff... do you perhaps have nothing going on this evening?" The friend had bought some Jeff Rowland components such as a Coherence preamp and a Cadence phono pre. Oh yeah, and these Audio Physic mono poweramps. Couldn't he just listen to them for a bit in my system he asked.
I had read a review of these amps in the German magazine audioPHILE but had forgotten about it. In speaking about the amps while connecting them the friend believed that they were traditional amplifiers. And during the listening tests, they didn't show any "digital" character. Only after remembering the article in the magazine, digging it up from my piles of mags and reading through, we found that indeed these amps use a form of switching amplification, referred to as class ND. They also employ a switching power supply.
And so it happened that days after me writing about "digital" class D amplification techniques, I came to listen to a set of amps that for the larger part don't sound digital at all. Are they actually digital? Well, they're called Class ND switching amps, which is a technique I know little about so whether they are in fact digital I will leave in the middle...
After first switching on - the seller mentioned that these amps need almost no warm-up time - they immediately surprised with a much fuller and richer sound than I expected. Even not knowing that they were in fact switching amps, I still had preconceptions based on their appearance and the fact that they were made to work with large Audio Physic speakers that need a lot of control in an amplifier. So I figured these amps would sound powerfull, controled, tight. And in a way they did. But not in a cruesome way. For starters the bass was full and weighty. Not as weighty as the Pass Labs x250.5 but easily a match for my Rowland model sixes. The Physics also had colour and richness of tone that I had not yet experienced before in a switching design. They did improve a bit after some playingtime, becoming more fluid, but indeed the differences were small and I would agree with the seller that they need practically no warming up. I have had a Jeff Rowland model 10 poweramp that also had a switching power supply but was traditional in terms of amplification. The 10 was also full in colour, as you would suspect from Jeff Rowland, but I still found it slightly too fast sounding. I think in terms of neutrality and precision it was probably spot on but for my tastes, it was slightly too lean. I blame this on the power supply. But back to the Audio Physics: it too has a switching power supply and even switching amplification but I find it much more ripe and full sounding than I recall the model 10 ever was. The Audio Physic is despite the full tonality a speedy performer, but not too much so. It is lively and nimble yet not aggressive at all. Detailing and soundstaging are more or less on par with the Rowland sixes and this is not where the big differences lie. Because differences there are. It is the shady territory of emotionality, air and finesse that I find the Physics slightly lacking. The Physics, full and natural though they may be, still sound somewhat measured to me. I don't find myself involved as much as when listening to my Rowlands, or to the Pass x250.5 for that matter. Both these amps sound more continuous, more fluid and, for a lack of a better word, more "analog" than the Audio Physics. But to put things into perscective: the finesse and air I'm talking about are aspects heard only in comparison to my Rowlands. If you would compare to many other amps, I suspect that they would simply beat them in all respects.
These amps do not have the lean sound that I heard in the other digi- I mean switching amps. The Audio Physics sound, well, physical. Theye have a full colour pallete, with great bass on par with my Rowlands. Also detailing is pretty good and they even have a warm and inviting character. The only things missing are the refined subtelty and air in the treble that the Rowlands are capable of.
It would seem that one or my greatest beefs with switching amps seems to have been overcome. By amps made in 2004 that were admittedly 15000 euro then. We may see more developmens here and probably ultimately the demise of class A/B. Which is fine by me, as long as the resultant amps equal or maybe even better traditional designs.