Zu Omen Defs and Ice Amps?

"of negative feedback switching power supply power amp."

It makes me suspicious of "negative placebo effect" when somebody has already opinion on switching in general.
Switching supplies are the same thing as class D amps. In addition to efficiency they have line and load regulation that linear power supplies are lacking. Latest $13k Rowland 625 - class A/B amp uses switching power supplies.

Noise from switching supplies is easier to clean because of higher frequency - that's why Rowland uses them in preamps where efficiency is of secondary importance.

Linear power supplies, if you thing about it, are really switchers operating at 120Hz poluting with 120Hz strong narrow current spikes of high harmonic content. This high harmonic content in addition to very high rms/average value ratio calls for oversized transformers. On the other hand ferrite transformer at 100kHz can carry 10x more power than toroidal 60Hz transformer of the same size. I would speculate that switching power supply, now days designed with zero voltage/zero current switching, got bad rap from extremely crude switching supplies in computers.

Why then linear supplies are still so popular? - for two reasons:
1. mistrust in new technologies (that was just expressed)creates demand for old technology (if it's heavy it has to be good).
2. any idiot can design linear supply - not so with the switcher (very complicated).

As for negative feedback - there is very little of it in class D since ouput is very linear by definition and output impedance is very low (inherent since output Mosfets always connect speaker to low impedances (GND and VCC). Iceamps have two feedbacks. One controls the timing of free running oscillator while the other is traditional analog one with perhaps only 20-30dB control.

So if anybody is objecting to class D technology or SMPS I'd like to add that delta-sigma converters, SACD and DSD operates on the same principle (Pulse Width Modulation)

For the record:
It is correct that very powerful amplifier, like our Musician III, can be rather poor match for the high sensitivity speakers. This why each and every Musician III leaving factory (sold new or after upgarde, repair etc) is tested on 98 dB sensitivity single woofer speakers and not on difficult to drive ones.

Many believe, I suspect, that all class D amplfiers have, and I quote: "....negative feedback switching power supply power amp " It is not so. Our Musician III, Mark Levisnon No.53 and few other class D amplfifiers use traditional "heavy" linear ones (Mark Levinson single monoblock weights, I believe, 170 lbs!).

It is not to say that there are no excellent switching power supplies (which can be used with class A,B,C,D,E etc amplifiers. One is that by Jeff Rowland (fully reguilated with PFC) and another, I know of is ours own which we use exclusively in our pro audio products (also fully regulated with PFC).

Moreover, I believe and I could be wrong that recent NuForce Ref 18 and Bel Canto 1000 Mk2 amplifiers use essentially older ICE Power based output stage(s) but improved the B&O switching power supplies by addition of extra capactitors and as I read people like the improvments but I probably should not go into subjective sonic opinions.

Simon

Simon - some Rowland amps (like 301) based also on standard Icepower modules with built in SMPS use Power Factor Correction supply in addition that converts 120Hz charging spikes common to 120Hz rectification to smooth full cycle mains current. In addition PFC converts 110VAC to almost 400VDC making for much better operation of Icepower's SMPS(lower losses).

Audiofeil, do you have problems reading? I said the Class D amps I HEARD sucked. Two of them. Both pretty favorably reviewed.

"If you believe all suck ..." I never said that. And I'm neither inexperienced nor ignorant. Stop being a jerk.

Kijanski and Krellman,
Why be so defensive? It`s a free market with many choices of amplifiers to choose among. If you prefer class D amps that`s a personal preference, nothing more or less. Others have tried them and found better sound elsewhere(no crime).

The fact that a particular reviewer likes the Spectron amp, OK, well he likes it. Some reviewers prefer SET,OTL,P-P tube or solid state, that does`nt add or subtract credibility at all. You guys bought what suits your taste, but it is`nt for everyone.