Re: Adding a SID

From: Levente Harsfalvi (
Date: 1998-01-02 00:58:41

>> chain SIDs by connecting the AUDIO OUT straight to EXT IN (strangely
>> enough the C128 PRG doesn't mention this...) but that didn't work for
>> me...
> This is from memory, and may be completely wrong, but don't you have to set
> a bit in some register to enable EXT IN?

No. Only, if you wanna filter the signal in EXT IN. Else, SID passes
it completely to Audio out.

But else, I see there are at least some DC couplers in the C64, placed
to the EXT IN and to the output lines. I won't beg, but the problem
should have been some kind of dc offset problem.

(If you, guys are sure that SID's can be connected by AUDIO OUT and
EXT IN without any extra parts then I guess I was wrong. ...But I don't
think. Once I made a 8580 go mad by simply pulling its EXT IN to a
constant dc level (with a trimmer connected to GND and +5v) so I suppose
it should be at least sensitive to dc offsets).

Happy New Year!


-- Arachne V1.20;beta 5 [Unregistered]

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