Martin,

there is a trimming potentiometer on the A-108 board that is used to adjust
the resonance so that self-oscillation just appears at the full clockwise
position of the resonance control. This trimming potentiometer is adjusted
for the default feedback (48dB output). If another output is used for
feedback the levels and phase relations are a bit different and you obtain a
different resonance behaviour as the setting of the trimming potentiometer
is optimized for the default 48dB feedback. This is why you have to amplify
the signal. You could try to re-adjust the trimming potentiometer for the
24dB feedback loop but then the setting is not optimal for the default 48dB
feedback loop.

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von marrtin606
> Gesendet: Mittwoch, 31. Mai 2006 21:01
> An: Doepfer_a100@yahoogroups.com
> Betreff: 1 Re: resonance for a108 when feeding 24db output
> into feedback input
>
>
> Dear Ingo, Bakis,
>
> you're of course right I don't need the feedback to get some form of
> resonance - but the point was to understand why i couldn;t get
> resonance using only 4 poles.
>
> I'm pretty sure the feedback is internally patched to the 48db -
> apart from the manual and schematics suggesting this, you can also
> try this by directly patching the 48db out to the feedback in: you get
> just the same as when nothing is plugged into the feedback in.
>
> > if you want, of course, you can patch the res input
> > with any of the filter outputs, for different
> > resonance behaviour.
> > regards,
> > Bakis.
> >
>
> That was precisely what i was trying to do, but didn't get much
> resonance. And that surprised me, because 4 poles/24db should be
> sufficient for that.
>
> I found out now that if I amplify the 24db signal a bit before feeding
> back (with a vca or externally), I also can get into resonance using
> only 4 poles. I'm still curious to hear what other 108 users find!
>
> Cheers Martin
>
>
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>