[sdiy] ot: class d audio amp

[John L Marshall]

Class D is commonly used in the modulator of AM broadcast transmitters. It
gets rid of the huge modulation transformer. A 10kW transmitter will require
about 6kW of audio.

Take care,
John
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----- Original Message ----- 
From: "Czech Martin" <Martin.Czech at micronas.com>
To: "Harry Bissell Jr" <harrybissell at prodigy.net>
Cc: "Sdiy (E-mail)" <synth-diy at dropmix.xs4all.nl>
Sent: Monday, October 20, 2003 9:38 AM
Subject: RE: [sdiy] ot: class d audio amp


> No, it seems that by clever signal processing
> you can get rid of a lot of artefacts,
> thus delivering quite good sound at least for
> woofers (in the Nx 100W area).
> When the needed frequencies get higher, the
> distortion (or sideband) problems get worse.
>
> This seems to need a lot of DSP computing.
> I'm looking for the range 20Hz-100Hz, where
> the problems are smaller and a PWM solution
> of 1st or second order migh suffice.
>
> I wonder if some of these devices are not
> jamming transmitters ...
> so officials will stop you from running them
> because of EMI.
>
> m.c.
>
> > -----Original Message-----
> > From: owner-synth-diy at dropmix.xs4all.nl
> > [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Harry
> > Bissell Jr
> > Sent: Montag, 20. Oktober 2003 18:13
> > To: Magnus Danielson; david.k.cornutt at boeing.com
> > Cc: synth-diy at dropmix.xs4all.nl
> > Subject: Re: [sdiy] ot: class d audio amp
> >
> >
> >
> > --- Magnus Danielson <cfmd at swipnet.se> wrote:
> >
> > > You don't want to know what class D is!
> > >
> > > Cheers,
> > > Magnus
> >
> >   I have a prototype class D amp... its good
> > for 875KW (short term peak)...  It switches at 1.2KHz
> > so its a little noisy but what the heck, its good
> > enough
> > for rock and roll...
> >
> > (actually its a welding control :^)
> >
> > Class D seems like an 'acceptable' idea for a laptop
> > computer where the sound is going to be lousy anyway
> > becaise of the massive 1" speakers...
> >
> > In a tiny chip it might be quite workable, but scaled
> > up
> > to audio amp size, the parasitics are likely to make
> > the
> > project quite unworkable. I assume that for a project
> > to be good for "diy" it should work at least as well
> > as a commercial unit (or be made entirely from old
> > radios or something else from the salvage bin - in
> > that case a little reduction in performance may be
> > acceptable for novelty reasons)  :^P
> >
> > H^) harry
> >
> >
> >
>