Digital Amps? Marketing Hype?

My basic electronics are rusty, but as i recall amplifiers were classed by the amount on time they conducted during a single cycle of the input waveform (a sinusoid for simplicity's sake). The term digital implies discrete states,on/off, in this case the output device (tube/transistor). It may only be semantics we are arguing, but if so, then only class A amps can be truly be called analog since all other classes are on/off for portions of the cycle. In this sense, they are digital; however, by convention, they have never been described as 'digital'.
It seemed to me to describe an amplifier as digital was to suggest a completely new design that did not encompass the class designations as generally accepted.
So you are right Kr4, I do need to do some research; however, it seems to me that class D amps are not digital but rather 'described' as such. I am not familiar with the digital ammps you mentioned, but it seems they behave as DAC's. That is, they pesent to the speaker load a signal which approximates an analog signal. It is the physical limitations of the drivers (load) which actaully produce an analog signal. Your thoughts?

Thanks for the links Voodoochile! The Spectron site in particular has a good desription of the basic theory underlying their design. In short, the input signal is converted to the digital domain, then amplified; hence the moniker digital amplifier. Both digital and analog input signals are converted to PWM (Pulse Width Modulation) format and then modulate a carrier. The resulting signal is then amplified to output levels, and filtered to remove the carrier. Note that the output signal is in fact a square wave.
There are of course merits to this design because class D amplifiers are efficiency champs. Die hard 'analog' audiophiles may have issues with so much DSP (Digital Siganl Processing), however DSP chips have advanced strides in the last few decades. Indeed, audiophiles routinely talk about 'analog' sounding CD players which actually benefit from advanced DAC and DSP chips. Personally, I love my 'analog' sounding CD player and would love to hear these new digital amps. It would be interesting to hear from anyone who has compared the sound of the analog vs digital inputs on the Spectron.