[sdiy] Self-oscillating

[Fredrik Carlqvist]

Hello Niklas,

I have no experience with this exact circuit, but I made a similar one from
Elektor once. 

I think the trigger should be a ground to positive going pulse. The
resonators are edge triggered. The pulse should be fast rising. 

Most of the drum sounds are high-Q band pass filters. When you adjust Q, you
adjust the feedback, and its self-oscillation tendency. The frequency also
changes, but the main purpose should be to set the decay time of the drum. 

If you want to change the frequency, you can change the capacitors. 

To get rid of the self-oscillation, check the capacitor and resistor values
above IC1B. I would guess that one of them is wrong, or that the + and -
inputs of the OP has been reversed. 


Fredrik C