Class-D or switching amps, any opinions on??

Magfan - I don't know if Mosfet configuration alone can be considered topology. Icepower uses full bridge vs. half-bridge on Hypex. Some people claim that full bridge sounds more "tube like" but also places half of the supply voltage on speaker terminals and in addition cannot be bridged.

Bobrock - Bass is one of the stronger points of class D. The issue is not if class D is best sounding but how does it sound for the money and if YOU like it. If there would be something really wrong with it (as Audiofeil implies) Jeff Rowland would not switch whole production to Icepower. Class D sound is very clean and revealing - will show deficiencies in your system.

As for the amp being "switching" or using switching power supply - every linear supply is in fact switching supply operating at 120Hz.

Main problem of class A/B is very high gain before feedback (up to 4000) that is about 10x higher than gain in class A amp (as low as 200). This high gain, in presence of limited bandwidth, is causing some overshooting on high slew rate pulses (TIM distortion). As a result of this amp produces/enhances higher order odd harmonics - that our ears are very sensitive to, making sound sharp/unpleasant. Tube amps on the other hand enhance even harmonics making sound wonderful on voice or guitar bad worse on instruments with complex harmonic structure like piano (sounds like out-of tune). Class D or A are likely neutral.

Love my Class D Gilmore Raptor monos. Clean and clear, with gobs of power and a sound that is smoother than I could have imagined. 93% efficient as well! They use huge toroidal power transformers and weigh 37lbs each, a lot of weight for class D amps. I've also owned the stereo model, the Raven -it has a similar sound to the raptors, but only half the power.

When I did the audition for the Raven, I compared it to Nuforce ref 9 V2 and an Atmasphere OTL tube amp. The Gilmore sounded more like the Atma than the Nuforce (which was harsh to my ears).

Gilmore Amps

Check out the Nuforce 9SE V2 amps. Great sound and good value.
I just sent mine for the V3 upgrade. Should be very interesting.

" ... they don't mimic the special quality of tubes -- a kind of creamy sweetness in the harmonic presentation. It is easy to understand the appeal of that tube sound; it has had a grip on me for years. But what the Spectrons do is, to my mind, ultimately even more impressive....[they] have a crystalline purity in the reproduction of every voice and instrument that sounds more to me like the essence of live, unamplified music -- which I attend, on average, more than once a week year-round-- than any other amplifier, at any price, based on any technology, that I have ever heard"

-Blue Note 2009 Award for Best Amplification by Enjoy The Music to Spectron Audio amplifier - http://spectronaudio.com/

John Ulrick of Spectron is the inventor of class D audio amplifier in1976.

Check their awards and professional reviews on their web site and do Audiogon search for the owners comments/reviews.

All The Best In Your Search

Rafael

Here are some interesting links:
The International Rectifier module has a fullbridge / halfbridge selector switch for those who can't decide!

https://ec.irf.com/v6/en/US/adirect/ir;jsessionid=74D07C3679B3902FCD3E847F05518E49?cmd=catSearchFrame&domSendTo=byID&domProductQueryName=IRAUDAMP7S

Here is another link with several articles on 'd' amps.

http://www.irf.com/product-info/audio/classddesign.html

I have the IR reference board out in the garage, awaiting a power supply. I will be able to directly compare with an ICE moduled PS Audio GCC integrated, which I will probably be forced to use as a preamp! Awaiting funds to build a +-55volt ps.