Class-D amps - a different re view

Thank you, Atmasphere. If I were building amps, I would go that route. The closest thing I have to having that capability is a remarkable CD produced by the Royer microphone company. They purportedly transposed master tape recording to CD. I know, it isn't the tape.

The point I am attempting to make, is knowing what a live musical instrument sounds like, you don't need an intermediary such as a tape. Take my daughter's viola, for instance. If, on your playback, you cannot hear the subtle roll of horse hairs from on edge, to flat, and all points between, you are missing a whole lot in musical phrasing. You will also learn to look for the proper amount of resin.

I can see where a master tape could come in useful. The sound of the viola is indeterminate. They all sound a bit different from each other. There is no one tonal indicator.

It should go without saying, no matter the recording, wires and speakers play an enormous part in bridging the performance with a system's There is not a speaker made that can sound absolutely real. The closest I have heard is my own.

Muralman1, you're in a good position to record that viola- and then play it back. *Thats* what I'm talking about. You already *know* what the instrument sounds like.

That's the technique I use when I am auditioning anything- speaker, a tweak in one of our products, a class D ampilfier- whatever. Sure, I play a variety of recordings, but its always useful to be able to play one where you were at the recording session.

To address an earlier comment- the distortion that a tube makes is not something that is cast in concrete. I have found that quite a bit rests on design consideration as well as materials. Not all tube amps have a predominant 2nd order harmonic- that's really a character of SETs. Push-pull amplifiers have even-order cancellation.

If you look at the distortion makeup of a lot of the class D modules, the distortion can be quite high for a 'transistor' amplifier. We have a module here that is 10% at full power. We've not measured the spectra, but I can tell you that the distortion is under 0.5% or so to about 50% of full power. The IM is actually higher than measured on our own production amps. Of the two, IM is usually more audible than THD. The appearance is very much (in the case of this module) that the ear is ignoring a lot of the THD, i.e. it appears to be even-ordered. IOW it seems to have a lot in common with SET amplifiers! I thought you might find that interesting...

By no means is the module that we have (Phillips) representative of the entire field. It would be interesting to see if there is a correlation either negative or positive with what we hear in these amplifiers as opposed to what is measured! A negative correlation, FWIW would put the behavior in the same realm as tubes, where much of the distortions made are ignored by the human ear.

Hi Vince, that's exactly my point. The sound of rosin for example is extremely faint and can be heard clearly only if you 'are' a microphone, or you are sitting/standing so close to the performer to be socially unacceptable under most circumstances. most concert goers will never hear the rasp of rosyn from the 4th, 12, 30th, or 50th row behind that plynth. . , particularly if they are surrounded by other listeners wearing sound absorbing winter clothing. Besides, what is 'real'? What I can hear when in a good day without tinnitus I can outperform audiometric equipment? or what's real is what the average middle age listener hears with a 12,000Hz cutoff, or what my dog can hear with a bandwidth of perhaps 50Khz. Or perhaps the perfect ears are those of a microphone? Which one? How sensitive? With ewhat dispersion, with what kind of bandwidth? Even the most perfect recording is by necessity just a cropped, filtered, an edited 'view' of reality containing selective enhancements. Nothing wrong with that, provided that we realize that our own perception IS NOT reality, but merely a useful and partial interpretation of it.

I have grown wearie of reading the black&white cartoonesque audio manifests of those who seem to be wanting to ram facile editions of some kind of Audiophile Pravda down my unwilling gullet. When I really want to hear the 'Truth' I'll find me a Church. . . for the time being, music and the quest for beauty may suffice.

Tvad, I have a Royer's Microphone demonstration disc. It covers the different microphone positions, and their affect on the final sound. Recording is an art in itself.

On solo acoustic instruments, with a uber-resolving system, you can indeed hear the rosin's stickiness, and those faint bow angle tonal tickles. That is what I want to hear, and that is what I have.

Orchestral staging is quite different. I am careful to choose a volume level that is compensatory to the distance between my speakers, 7.5 feet. That puts me on first balcony.