Zu Omen Defs and Ice Amps?

I will throw out a general statement about Class D is mid fi at best. I have listened to way too many Class D amps and to two that have been mentioned in this thread and they have big power but they do not deliver the quality. The problem is that manufacturing good old fashioned power has gotten very expensive here in the USA for the average US citizen. To build a strong Class A or AB amp you need to dissipate a lot of heat and that requires lots of machined aluminum metal, that is very expensive. It was not a problem until the dollar sank and our economy went south. The reason that high efficiency speakers are popular these days is that you can use high quality old fashioned lower power amps and get better sound than what you get from a 1000Watts of negative feedback switching power supply power amp. The manufactures are also struggling to make stuff people can afford. Under normal economic conditions I they would be a place for Class D but it would not be in high end sound systems. I am not saying that Class D is a bad technology what I am saying is that it needs to improve. I remember when I got my first CD player and I had a first pressing of The Police Synchronicity on Vinyl and bought the CD. What a let down the CD was. No one believed me that the vinyl record blew away the CD. My friends thought I was crazy. What was scary is that I had a Yamaha CDX 1100U CD player and a very very cheap Technics belt drive turntable with a cheap Ortofon p mount cartridge that sounded better then the summmer job's wages I saved to buy that Yamaha CD player.

George,

You're absolutely right! My Spectron is only mid-fi at best!

The question is, what does that make Karan, Burmester and Pass, since I chose it over them?

Why don't you e-mail Wayne Donnelly at "Enjoy The Music" and tell him that. After all, he chose it over the very expensive VTL mono-blocks.

Then, go and e-mail all of the reviewers who've given the Spectron very nice reviews that their hearing is obviously impaired.

Mid-Fi my A--! I'm glad that I've never been to your stereo shop, who knows what you consider as high-end.

Chuck

"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).