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

I thought the question was "Does anybody have experience on Class-d or switching amps vs either a/b or traditional amps??" The question seemed general enough, not technical in nature. "true digital" seems to me as elusive as "true class A". Hard to get folks to agree on the term. Class D means "not an analog amp" to most of us. FWIW Tact amps can be digital input only, or may have an analog input in addition.

Hello Kijanki:
Many people participated in the development of class D technology. However, as journal Sound & Vision reported in "50 Greatest A/V Innovations", January 2008 issue:

"DIGITAL AMPLIFIERS

Going back to the Infinity SWAMP-1 of the mid-1970s, digital amps have had a checkered history, but they seem finally to have turned the corner in terms of reliability and performance. Highly efficient and cool-running, they promise to play a bigger role in the future."

John Ulrick at that time was chief designer of Infinity and SWAMP is his amp. Moreover, he introduced SWAMP as the first commercially available class D amplifier into the (hi-fi) audio world at CES 1974.

So without taking a credit from anyone who worked in the filed of this technology, Spectron chief designer John Ulrick is generally recognized as the father of Hi-Fi class D audio amplifiers

All The Best,
Rafael

Have a PS Audio Trio C-100 Cullen modded(stage III) hooked to a pair of Quad 11Ls. They have really brought the Quads to life. The amp makes them seem faster without diminishing the musicality.
Have Bel Canto Ref 1000s hooked up to Reference 3A Grand Veenas. I'm waiting for a pr of Wyred Reference amps(class D) to be built. Have both an analog and tube front end.

Dod - I just wondered why you call him "inventor" when class D is known from 50's and Sinclair X-10 was sold in stores both as a product and a kit in 1964 (12 year earlier). It was followed shortly by X-20.

Samujohn - class D does not mean "not analog" - it is purely analog in 99% cases. The fact that output stage switches between two voltage levels doesn't make it digital because time and not the voltage is analog quantity here. Word "digital" was used by uniformed people and became popular name for class D. I don't have anything against calling it "digital" as long as you realize it is not.

As for digital inputs making amplifier "digital" it would be true for any amp. Combining in one box DAC and tube amp would make it "digital amp" - nothing to do with a class of an amp.

Magfan: The new NAD M2 ... operates in the digital mode, which I expect to be the real definition of 'digital amp'.

Agreed 100%. My previous post was not worded as precisely as it should have been, to the extent that it implied anything different than your statement quoted above.

The signal path through a digital Class D amp will consist entirely of either digital signals or switched waveforms, from the amp's input to just before the low-pass reconstruction filter which reconstructs an analog waveform at the amp's output.

However, the literature at the Tact site appears to indicate that their amplifiers do exactly that. For instance, see the section on page 8 of the 2150X Manual entitled "How Does It Work."

I know of no other Class D amplifiers besides the Tact's and the NAD which you mentioned which can properly be called digital amplifiers, although there certainly may be a few isolated exceptions that I am not aware of.

Best regards,
-- Al