As part of my 606 modification project, I decided to draw up this schematic of the bass drum circuit, using the free software ExpressPCB. On the basis of the equations from Thomas Michaux's hyperreal post, OSC 1 is at 60 Hz and quite short (Q = 7), whilst OSC 2 is at 130 Hz, even shorter (Q = 3), and with a lower amplitude (compare R36 with R60). You can hear it here. Various people have suggested pitch, decay, and other mods for this circuit. I'll be looking into those in a bit, but wanted to understand (and be able to retrieve) the original 606 BD sound. Accent is (I think) achieved by a higher voltage (and possibly longer) trigger pulse.
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