[sdiy] Compensating output level for Q

[Nicholas Keller]

I have a synth that seriously jumps in volume when its filter oscillates.  I know that later generation chips had a way of compensating for this change, keeping the level constant regardless of the resonance setting.  Is there a circuit I could add to my synth that would perform this compensation?  I could use an audio limiter perhaps, but I'm concerned about clipping and squaring off the waveform.  I'm wondering if anyone knows how these chips did it, like the SSM2044 and the later CEMs, and if I could build a similar add-on circuit for my synth (and possibly other modules I have, like the Doepfer A-102).   

I have an idea of adding an envelope follower (inverted) and VCA.  Maybe that's how it was originally done.  

Thanks,
Nick