On Sat, 08 Mar 2008 10:32:12 +0100, (Martin
Schöön) wrote:

(Don Pearce) writes:

On a more serious note: What about all those class-D amplifiers?


99.9% of them are in subwoofers. As for the rest, they seem to pretty
much stop at 20kHz, where the clock filtering has to get started to
keep EMI down to a reasonable level.

I have seen allegations of RF-output from class-D amplifiers.
Here is an example:
http://www.hificritic.co.uk/scene/news.aspx
(You have to scroll down beyond the middle of the page).

Here is a pro-class-D article in the guise of a portrait of
Bruno Putzeys. Here it is claimed that no RF escapes Putzeys'
handiwork. Not mentioned is the fact that the writer has built
an amplifiers based on UcDs...
http://spectrum.ieee.org/feb08/5953

Well, HF clocking is a rather different subject to extended frequency
range.

Neither of those articles is particularly satisfying to me - the Hi Fi
critic one in particular makes all sorts of claims, but fails to
substantiate them with test results (which they presumably have).

As you say, allegations.

d
--
Pearce Consulting
http://www.pearce.uk.com