[sdiy] Formant 24dB filter

[Magnus Danielson]

From: jhaible at t-online.de (jh.)
Subject: Re: [sdiy] Formant 24dB filter
Date: Tue, 5 Jun 2001 23:02:57 +0200

> > My Formant's 24dB filter has the same problem. I have only thougth
> > about it some, but have not spent quality time on it. I too want to
> > wash out this problem out of my Formant.
> 
> I don't have the schemos in front of me. Does it have noninverting
> opamp buffers after the OTAs ? Then you know where the problem is ...

Sure, it has non-inverting buffer on the output, but the input is
inverted. What was you hinting at? Incorrect feedback-sign or what?
Please speak up on the full story...

Hmm... LOADS of 741s and CA3080 and not a single offset trimmer in
sigth... yeeeehaaaa... toss in the positive feedback of the Q pot and
we are in big latchup buissness... tossing in DC offset trimmings on
the 741s alone can be done, but the CA3080s are badly in need of
compensation. Maybe just toss in compensation on the input op-amps
would do enought of the trick?

Cheers,
Magnus