Negative Feedback a deal killer?

Magfan - local feedbacks are always better than global one but their application is limited.

Class AB amp design has to start with excellent linearity and wide bandwidth since one of conditions to eliminate TIM is to limit bandwidth at the input to one amp had before feedback was applied. Feedback can fix inherent class AB problems like "gm doubling" (different gains for small and large signals) but cannot fix poor design. AFAIK there is always some form of feedback (local one) even in zero feedback amp.

Atmo / Kij,
Processing your replys now........and they agree generally with what I had heard, which is why I brought it up.
Talking about feedback without qualification doesn't help a lot.

I also have felt that the B&O 'd' offerings have more in common than differences, no matter WHO packages the modules and what mods are performed.

One question though, about 'd'. For at least the ASP modules from B&O, they come WITH integrated SMPS. How do you get around that? Go to another module...the ASC(?) series which has no PS included?

Magfan - ASC series has also SMPS. I think that it was AP series but now Icepower makes different modules.

B&O SMPS are pretty good - very quiet (zero voltage / zero current switching) and very strong (1000ASP can deliver 40A output for 0.5s). What people often don't realize is that SMPS supplies are line and load regulated while linear supplies aren't. Linear supplies require a lot of capacitors to keep voltage steady and filter out 120Hz. They are also noisy since switching is done in audible frequency at max voltage. Linear supplies are also huge with big transformers. Small 1"-2" dia. toroidal transformer at 100kHz can deliver same power as huge toroidal transformer at 60Hz.

Best Icepower amps use 1000ASP with addition of extra supply that feeds over 400VDC. From what I read it has positive effect on the sound but module still uses its own supply. It is perhaps bunch of extra capacitors at high voltage (low losses).

Smaller Icepowers like 200ASC used in my Rowland 102 have higher carrier frequency and therefore wider bandwidth.

If you plan to use one, you might want to investigate input circuit that increases input impedance from 10k to 40k based on THAT1200 instrumentation amp (tiny board). That's the only Rowland contribution (other than beautiful case) to my amp.
I have to admit that he deserves credit for recognizing genius of Karsten Nielsen and B&O company. B&O was so fascinated with the project that they sponsored Nielsen's doctorate and gave him shares of company - first time in 70 years of B&O (being private company).

I've lost track of what B&O makes. Here is link to ASP module....I suspect as used in my PSAudio GCC series integrated::

The data sheet lists 50v and 80v outputs...with which to feed the extra, non power supply equipped modules. The 80v is listed as 7 amps, If I remember correctly. These numbers are with the 'home' amp having zero output....

http://www.icepower.bang-olufsen.com/files/solutions/icepower500aspdata.pdf

The GCC series is a so-called variable gain design. The input circuitry is handled thru something called a 'gain cell' which I HOPE takes care of any impedance mis-match with any source connected.
The balanced inputs from my CD player are wonderful....

Thanks for the responses. My speakers are Coincident peII's w/ a flat 8ohms load and 92 db. Aljordan's comment about znfb used with easy to drive speakers is true, I believe at least in my experience. The Unison would be used on the same speakers. I try to stay away from "hard to drive" speakers as it limits your amp choices too much. I prefer SET amps, or tubes in general. Atmasphere hopefully someday I can listen to one of your amps, no dealers in my area.
Thanks
Mike