[sdiy] SID question

[Michael Buchstaller]

Hello list friends,

this week i had some spare time and decided to invest it into making 
the final verison of my monovoice (SID based synth).

Most of my prototypes have been built with the "newer" 8580 (6582) version
of the SID, with 9 V power to the chip. They worked all fine.
Now, i made a board with a 12 V regulator to use the "older" 6581 chip.
Here, the output from 5 of 7 SID´s is very muted (approx. 0.1Vpp) and
sinusoidal shaped. (as if the filter cutoff frequency would ba waaaay down)
2 of the Chips are louder (approx. 0.25 Vpp), but similar in behaviour.

Changing the regulator to 9V and replacing with an 8580 cured it.

Now, i ask myself if i have really 7 bad SID chips ?
Or are there more differences between the older and newer SID´s ?
Maybe the 6581 needs smaller filter caps ?
I used 1 nF polystyprene caps, then 1 nF ceramic discs.


-Michael Buchstaller