[sdiy] ot: class d audio amp

[harrybissell]

Watch out when you try to run a 50 foot speaker cable... you might
find out that you have a lot of noise issues (in everything else) when your
filter chokes (speaker coils) are located so far away...

you might even induction heat metal objects in the cable path...

its very inportant in these apps to keep stray inductance (and capacitance
for that matter) low...

H^) harry

(now having a bad day with a motor drive switching at 8KHz on a 15'
cable... guess what happens later this week when the 50' cable arrives :^)

Alex Stettler wrote:

> Hello,
>
> I just built a sort of 3-channel class D amplifier. I use it to generate
> 3-phase / 450 Hz power
> for my Alcatel Turbopump. It is based on a look-up-table (calculated in
> MATLAB), clock-generator
> and driver / MOSFET-power stage. The whole amplifier is very efficient. With
> full output power
> of 300 VA (cos(phi) is estimated to be about 0.7) the losses in the power
> stage are only about 12 Watts.
> Also the sinewave is very nice, watched on a scope. I didn't measure the THD
> so far, but I'll do in the next
> days. In my application the amplifier is even simpler, because you don't
> need the output filter network.
> The stator winding of the pump motor plays the role of the lowpass-filter.
> (BTW: Most modern frequency converters for ac-motors are simpler forms of
> class-D amplifiers)
> As a future project I intend to build a audio class D ampfifier as you, too.
> Because this type of amplifier is interesting
> in two ways: You can get 800 Watts or more of audio power out of 1U / 19"
> case (high power per volume) and because of the working principle and the
> design of the different components involved with this type of amplifier
> (Switching Mode Power Supply, PWM-Modulation, DSP-Processing,
> Control-Circuits etc.)
> But first I've two finish my SMPS (based on L5991) for my 3-phase
> generator/amplifier.
> With the experience I've made with this class of amplifiers, I'm very
> optimistic to get a class D audio amp running with low THD and other good
> technical specs. But in comparison to the amp I've built, the audio capable
> version will need much more of design effort, because of the much bigger
> bandwith and other differences. My generator/amp has only to cover a
> frequency range of about 400 - 1200 Hz.
>
> Regards,
> Alex
>
> > -----Original Message-----
> > From: owner-synth-diy at dropmix.xs4all.nl
> > [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Czech Martin
> > Sent: Monday, October 20, 2003 4:19 PM
> > To: Sdiy (E-mail)
> > Subject: [sdiy] ot: class d audio amp
> >
> >
> > Could anyone point me to diy audio amp project switch class D?
> > So far I only could find some theoretical paper or commercials.
> >
> > m.c.
> >