On Wed, 10 May 2000, David L. Nicol wrote:
> volodya@mindspring.com wrote:
>
> > Unlike sound cards that have from 256 to 65536 gradations (or
> > more) pc speaker has 2.
> >
> > Vladimir Dergachev
>
>
> But is it not possible to drive the speaker for a very very
> short period of time, emulating an amplitute gradation
> with pulse-width modulation?
>
>
Yes. And my very first Linux-box had that software (version 0.99). It
played music quite well right out of the tiny speaker.
When I got my first XT clone, one of the first things I did was
to make it 'talk'. There were no 'wav' files, I sampled a mike
preamp at 10 kHz, made an 8-bit A/D converter using the printer-port,
captured the resulting data into a file, then I could play it back
into the speaker by varying a 10kHz pulse-width from timer channel 2
(the one connected to the speaker). All the source-code and the
schematic was published on my BBS in the 80's.
Even though the distortion was probably greater than 10%, and the
10KHz rate with within audible range (the speaker becomes a LPF),
the voice sounded quite okay.
Now practically everybody has BOOM-BOX Audio boards. I still haven't
bought one.
Cheers,
Dick Johnson
Penguin : Linux version 2.3.41 on an i686 machine (800.63 BogoMips).
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