Jeff Rowland amp in unbalanced mode

Guido - I don't thing is changing anymore but I haven't counted hours.

I wonder what came earlier 312 or 501. It is possible that Rowland requested (or made) some changes to Icpower module based on previous experience. There are also some external components like input transformer and possibly mains filter. It would be interesting to listen to the same amp with and without PC1.

As for steril sound - my experience is very limited but I suspect that very clean sound might create impression of sterility or lack of dynamics (distorted guitar is lively in comparison to clean jazz guitar). When I upgrated from integrated solid state amp to Benchmark DAC1 + Rowland 102 I got impression that some instruments are missing - it sounded too clean.

Hi Kijanki, 501 were introduced prior to 312. Both use ASP100. However 501 monos are relatively basic design, while 312 costs almost 3x the 501s, and is much more sophisticated and, includes integrated PFC among other things. G

Guido - so it's entirely possible that sound improvements you heard are due to something different than PFC (wiring, shielding, power filtering, input transformer or mods to Icepower 1000ASP module). Often companies don't apply improvement to less expensive modules for marketing purpose (more money - better sound)

Guido - I forgot about another important factor - speakers. I heard that Icepower sounds great with some speakers (like for instance Usher BE-718) and not so great with others. It might be sensitivity to type of load speaker is presenting. Initialy first class D called class T had output filter outside of feedback having low Damping Factor and big dependance on the speaker impedance characteristic. Icepower has output filter inside of the feedback but nothing is 100% perfect. It would be great to compare 501 with 501+PC1 on the same speaker. How PC1 is attached to amp - is it external or requires mods to amp?

Kijanki, I suspect that the more refined sound of the 312 over the 501 is caused by a reasonably wide variety of technical factors, only one of them being integration of PFC. It is worth pointing out that PFC has now being integrated in the Continuum 500 integrated, which costs about half the 312 and also contains a Capri-like front end and some bulk output capacitance not implemented on 312. What frequently happens with technology is that novel design solutions are first tried in higher end devices, and then are gradually migrated to more attractively priced implementations. G.