Korg-35 clone up and running

[jorgen.bergfors at idg.se]

>I think you may have the trannys in wrong. This filter is much hotter than >that. Maybe cv problems???....bad opamp??

Thank you for your suggestions. I'll check transistor orientation just to make sure. But the output can't be that much hotter. The diodes will limit the output voltage to +- 0,6 volts. I did get a bit less than that though. It is hardly a bad op-amp, as both filters behave exactly the same.
I worked a little more on it yesterday. With 30 times amplification it will output maybe 15 volts p-p while oscillating. But with no resonance the signal will be 10 V p-p if I don't drive it into severe unlinearity. Of course I can get more if I really crank it. I'm going to add a switch that decreases the input signal attenuation and output gain by a suitable amount. So when I want it to crunch, I just flick the switch.
As I said, the resonance isn't very impressive. But the filter makes a really nice synth horn sound with no resonance and moderate attack/decay times. The major flaw with this filter must be the thumping, caused by DC-shifts when the CV is changed. Even the key follow causes it to pop. Maybe I should add some lag to the keyboard signal, to make it less abrupt.
It seems the DC-shift causes the signal to drop out completely when you do gross and quick changes to the CV. Have anybody else noticed this? I suppose it is because the temporary DC will offset the opamp output and the diodes (D2, D3) will block the signal.

/Jorgen