[sdiy] SID question

[Rainer Buchty]

> Or are there more differences between the older and newer SID´s ?

No revision of the SID sounds the same... Not only there's a difference
between the 8580 and the 6581, but also between the various revisions of
the 6581. (And, of course, there's some religious thing going on which
revision sounds best :)

> Maybe the 6581 needs smaller filter caps ?
> I used 1 nF polystyprene caps, then 1 nF ceramic discs.

Depending on the revision, 470pF (6581) to 2200pF (8580) are recommended.
(A similar thing is going on for the buffer caps of the POT inputs.)

Apart from that, the 8580 is "better" designed and fabricated in a sense
that the 6581 was greatly suffering from DC offsets which clicked and
popped into the signal path when changing various parameters. OTOH, it was
especially this which led to the beloved 4-bit digi voices. The 8580 needs
to be hacked in a special way to produce truly audible 4-bit sample
playback through register 24.

See http://www.softwolves.pp.se/misc/arkiv/cbm-hackers/4/4670.html for a
discussion on how 6581 and 8580 differ.

And in case you're interested in the design story, see
	http://stud4.tuwien.ac.at/~e9426444/yannes.html

Rainer