Improving on Classic Amps

Cwlondon, actually class D amps are analog devices. . . the "D" is just a counter, like in A B [C] D. . . problem is that I have no idea where class C amps have gone (snickers!)
As for them being heavily discounted. . . some are, while some brands/models definitely are not. Yet, I do understand your natural mistrust for the diminutive. . . . I used to suffer of the same problem. . . and perhaps I still share some of it. . .after all, my JRDG 312 does weigh a hefty 80 Lbs. . . is this perhaps the reason why there are so few of them on Agon? (grins!)
As far as I know, the latest Levinson flagship runs in class D.

Thanks Guidocorona for clarification - from Wikipedia

"The letter D used to designate this amplifier class is simply the next letter after C, and does not stand for digital. Class D and Class E amplifiers are sometimes mistakenly described as "digital" because the output waveform superficially resembles a pulse-train of digital symbols, but a Class D amplifier merely converts an input waveform into a continuously pulse-width modulated (square wave) analog signal. (A digital waveform would be pulse-code modulated.)"

Naturally, as an audiophile, I am inclined to believe that any amplifier which is heavier, runs hotter and/or has dangerously sharp edges probably sounds better.

Also from Wikipedia:

"Class D amplifiers for driving subwoofers are relatively inexpensive, in comparison to Class AB amplifiers.

A 1000 watt Class D subwoofer amplifier that can operate at about 80% to 95% efficiency costs about $250 USD, much less than a Class AB amplifier of this power, which would cost several thousand dollars."

This second point might also explain some skepticism, heavy hype and promotion from certain manufacturers and the rapid fall in resale values for some.

Old school Class A amps seem to retain their value pretty well.

I do believe that the TacT amps can accurately be described as "digital" amps, that is if they are indeed amps at all.

problem is that I have no idea where class C amps have gone

Class C amplifiers very much exist, but they are not used in audio because they inherently have very high distortion. They are commonly used in RF transmitters, with their outputs fed into tuned circuits (tuned to the frequency being transmitted) which can partially filter out the distortion.

The letter D used to designate this amplifier class is simply the next letter after C, and does not stand for digital

Quoting from a post I made in a recent thread on Class D amplifiers:

Whether or not a class D amp is referred to as digital or analog is not related to its class D power output stage. What would properly be called a digital class D amp is one that can accept a digital input, and which puts that digital signal through some dsp (digital signal processing) to generate the modulation waveform that ultimately controls the switching of the class D power output stage. An analog class D amp would differ in that it would utilize an analog input and have an analog front-end signal path.

Regards,
-- Al

Thank you Al for solving the 'Great class C Caper'!

Cwlondon, like all other types of amps, class D range from 'bargain basement' prices like the subwoofer amps you mentioned, to the stratospheric. For example: Flying Moles used to be under $1K, Bel Canto Ref 1000 Mk.2 $6K, JRDG Continuum 500 $8.8K, JRDG 312 at approx 16.5K, Spectron monos with all the trimmings at $22K, JRDG 301 monos approx $30K, Levinson flagship (forgot model) in $50K range if memory serves. Interestingly, class D amps are somewhat less heavily advertised than other kinds. . . their growing popularity appears to be more of a word-of-mouth phenomenon.