Class-D amps - a different re view

The Von Schweikert demo is no more convincing. We weren't at the recording. The smart thing was to use a master tape.
Muralman1 (System | Threads | Answers)

The Von Schweikert demo worked in the following manner...

A live acoustic group preformed in a ballroom and was recorded. Then, the recording was played back in the same ballroom shortly after the live performance. Same room. Same acoustics. Same electronics. Same speakers. I believe this is precisely on point.

Nevertheless, I am absolutely certain you are still unconvinced. This is the take-away from the discussion.

11-15-07: Tvad
The Von Schweikert demo worked in the following manner...

A live acoustic group preformed...

Actually, they performed.

But if they preformed, it'd have been a really cool trick!

Muralman1, I am sorry you took offense at my comment, but if you look at my last post and your initial reaction, it will be obvious that you attached meaning where none existed.

My point was that if you go ahead and make good quality master tapes, you will be in a position to use those recordings as reference tools, for all the reasons that I outlined earlier.

Will the results mean something? I have no idea. All I know is that these tools were invaluable for me personally and others who have done the same thing.

IOW, a system may sound great, but its always in respect to what. When you have master tapes, now you have an absolute.

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.