96 Nicolas Collins
Put a Schmitt Trigger Inverter stage (from a 74C14 or 4093) between the
distortion output and the digital circuit input. This can clean up the input signal
so the circuit will track the fundamental better, rather than the noisy higher
overtones. If you use a NAND gate from a 4093 as a buffer, connect the output of
the distortion circuit to one input of the gate and tie the other one to + 9 volts, or
connect the output of the distortion circuit to both NAND inputs.
If the circuits still seem very noisy and tend to oscillate on their own, put
larger capacitors in the feedback loops of the distortion circuit (Cf). This will roll
off the higher frequencies and send the subsequent circuits a signal that
emphasizes the fundamental.
Having previously extolled the virtues of random circuit variation, I encourage
you to pursue free-style interconnection of “real world” audio signals with your
circuits – only please observe our “no-AC power” safety practice.