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Class D "digital" amps. Opinions on performance

#262
projectMalamute said:
They get these patents because it's not the same amp.
Click to expand...

Class D is a type, and NOT a specific implementation. There is no single way to design around the basic topology, there are evidently many ways to exploit a Class D approach, as evinced in the market over a number of years.

There is a huge gap between these two statements:

'pro sound companies are using a variety of variations on switching output stages'

and

'pro sound companies are using the same thing as this 200 dollar amp I bought at Guitar Center'
Click to expand...

What did that have to do with anything I brought up? I'm not especially interested in module-based MI stuff so much. So I haven't been talking about it. I've been mentioning instead a more mature sector of the audio market.
 
#263
greenboy said:
Class D is a type, and NOT a specific implementation. There is no single way to design around the basic topology, there are evidently many ways to exploit a Class D approach, as evinced in the market over a number of years.
Click to expand...

I understand that. What you are not getting is that 'class D' is a specific topology, not anything using any sort of PWM scheme anywhere in the circuit.

A Crown XLS is a class D amp. A Crown I-Tech is not a class D amp.

You see XLS amps in DJ rigs and band PAs. You see I-Techs in touring systems.
 
#264
Class B is used in audio. Usually it's implemented as class AB, where the output devices are biased with a slight amount of overlap in the crossover region (the zero-crossing transitions between positive and negative output voltage) to prevent a discontinuity between the positive and negative banks (known as "crossover distortion"). In some amps the output devices are controlled by a complementary pair of driver transistors. The driver transistors can be class AB while the outputs are very close to pure class B (i.e., almost no overlap at all, but with infinitesimal discontinuity), and this will reduce the idle and low-signal current quite a bit.

Douglas Self says class B can be done with the output devices precisely biased to cutoff with zero discontinuity, without doing class AB. I haven't gotten around to reading his proposal yet but IMHO he has a great amount of credibility.
 
#268
You are being intellectually dishonest and expecting not to get called on it because of your credentials, and you know it.

An I-Tech is a different topology than an XLS.

I've got a lot of people to buy RMX amps from you guys. That was my standard recommendation for good sounding at the expense of a little weight for years. Next system I build for somebody gets Crest. Congratulations.
 
#269
Intellectually dishonest? How?

Sure, an I-Tech is a different topology than an XLS (the later non-class AB versions). But they're both still class D.

Crown started using interleaved class D with their K Series back in the mid 90s. They decided to call it class I. OK, but it's still basically class D.
 
#271
Link Removed

Quotes from the link above:

"Class-D amps are switching amps. The signal is either on or off, not constant as it would be in an analog system. Because of this feature, sound quality is an issue."


"Because of its "all-or-nothing" nature, digital sound reproduction requires extremely rapid signal switching to reproduce sound accurately."

This article also cites references to it's sources of info on the bottom of the page.
 
#275
bongomania said:
Oh please NO, eHow is NOT an authoritative reference, it is just some crap written by bloggers and voted on by other bloggers, and it should NOT be brought into a discussion like this.
Click to expand...

See the cited references on the link at the bottom of the page!
(one is not found though; but the other is there)

Link Removed

Quote from link above:

"7 - Feedback
As I have stated previously, timing errors can lead to increased distortion and noise. This cannot be skipped and the more precise it is kept, the better the design will perform. Anyway, open loop Class-D amplifiers are not likely to satisfy demanding specifications, so (negative) feedback is almost mandatory."

PEACE
 
#276
Bob Lee (QSC) said:
Intellectually dishonest? How?

Sure, an I-Tech is a different topology than an XLS (the later non-class AB versions). But they're both still class D.

Crown started using interleaved class D with their K Series back in the mid 90s. They decided to call it class I. OK, but it's still basically class D.
Click to expand...

The words 'interleaved' and 'basically' keep showing up in your posts.

The first points to the fact that this is a different topology, whether you like it or not. The second to how you are intentionally trying to gloss over this fact.
 
#278
bongomania said:
Oh please NO, eHow is NOT an authoritative reference, it is just some crap written by bloggers and voted on by other bloggers, and it should NOT be brought into a discussion like this.
Click to expand...

I just browsed through the article. I don't know where to start. The author seems to misunderstand just about everything about class D and amplifiers.
 
#280
projectMalamute said:
The words 'interleaved' and 'basically' keep showing up in your posts.

The first points to the fact that this is a different topology, whether you like it or not. The second to how you are intentionally trying to gloss over this fact.
Click to expand...

Yes, it's a different topology. The audio output of your mobile phone is class D, too--again, a different topology. But class I--interleaved class D--is still class D, whether you say it's glossed over or not. Sorry, I really don't get what you're after.
 

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