Thanks folks, its good to know at least the filter is not faulty. Another thing on the list of modifications I will get round to doing one day!

Mick

--- In Doepfer_a100@yahoogroups.com , "okmog" <olli@...> wrote:
>
> > @ Ollie: it is my favourite filter. (Next to the wasp filter, that's
> > something different).
> > I use the A102 with very moderate resonance settings. I just love diode
> > filters.
>
> Wow, that's impressive. I really have to try them!
> Thank you.
> I think I should try them all! ;)
>
>
> > But the A108 is also very good. But the character is completely different.
> > It's like comparing apples and pears I'd say.
> >
> > On Fri, Jan 22, 2010 at 6:16 PM, okmog <olli@> wrote:
> >
> > >
> > >
> > > @Tim: WRONG! No, relax, I'm joking ... ;)
> > >
> > > @all:
> > > May I ask you by the way how you like the sound of the diode-ladder filter
> > > I mean do you find it more or less musical than the transistor-cascade e.g.
> > > for bass sounds or leads or so
> > > Last question: Does the Doepfer transistor ladder filter really sounds like
> > > the Moog filter
> > >
> > > I've read your paper about the comparison between the diode- and transistor
> > > filter, Tim. Good work!
> > >
> > > Ollie
> > >
> > >
> > > --- In Doepfer_a100@yahoogroups.com <Doepfer_a100%40yahoogroups.com>,
> > > "Tim" <timothy@> wrote:
> > > >
> > > > Hi Mick,
> > > >
> > > > > Can someone tell me if my A102 filter is acting correctly - The
> > > resonance seems to be set really high. The filter will self oscillate with
> > > the resonance set to just 4 (when the cut off is set between 3 and 6).
> > > > >
> > > > > Is this normal
> > > >
> > > > Yes, both mine behave similarly - basically there is way too much gain
> > > around the feedback loop.
> > > >
> > > > > Is there any way to adjust the resonance to a more usable range
> > > >
> > > > I tried a couple of things very quickly (the first one was spectacularly
> > > ineffective!). However the following seemed OKish: between C10 and Q7 there
> > > are 4 resistors - the 2k2 amongst these is R24 (the 'bottom one' if you hold
> > > the faceplate nearest you); swap this for a 5k6 say, which will cut the gain
> > > to a third, so it won't resonate until the pot is further round. A 4k7 may
> > > not be enough of a difference, and a 6k8 (I temporarily added a 4k7 to the
> > > 2k2) may restrict the range of frequencies at which it will oscillate.
> > > Unfortunately it will also reduce the output amplitude somewhat.
> > > >
> > > > To do the job 'properly' would mean re-vamping the entire 'gain regime'
> > > around the loop, which would require considerably more thought, and
> > > replacing maybe half-a-dozen or so resistors. My initial idea was to
> > > *double* R5 (the 10k in the middle of the only group of 5 resistors, central
> > > to the board), but this seemed to have little impact, mainly I think because
> > > the resonance pot is a 'law C' ('rev log'), and so naturally 'all the
> > > action' is in the first part of its rotation.
> > > >
> > > > Let us know if you have any success with this!
> > > >
> > > > Tim
> > > >
> > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>