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AW: [Doepfer_a100] Re: resonance for a108 when feeding 24db output into feedback input?

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  • Dieter Doepfer
    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
    Message 1 of 8 , Jun 1, 2006
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      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

      > -----Urspr√ľngliche 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: [Doepfer_a100] 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
      >
      >
      >
      >
      >
      >
      >
    • marrtin606
      Dear Dieter, Thanks, found the pot (p8), and am playing around to find setting(s) I like. It s an awesome filter by the way. Cheers Martin ... adjust ...
      Message 2 of 8 , Jun 3, 2006
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        Dear Dieter,

        Thanks, found the pot (p8), and am playing around to find setting(s)
        I like. It's an awesome filter by the way.

        Cheers Martin


        >
        > 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
        >
        > > -----Urspr√ľngliche 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: [Doepfer_a100] 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
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        >
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