Just built this little circuit to control my Moog Werkstatt. The plan is to make a MIDI-to-CV converter and add more CV outputs and of course a GATE output later. But before going further, I thought I'd ask if this circuit could be improved.
CV in this context stands for "Control Voltage" and is used to control the frequency of the oscillator in the synth. The Moog Werkstatt changes the pitch by 1 octave per volt.
The Atmel chip sends a 0–5V PWM signal at 133.333kHz. After filtering the PWM output it is scaled to -5-+5V (which is what the Werkstatt expects). I want to be able to tune the signal so therefore I let a voltage divider turn the signal down to roughly 4.5V and then I have an amplifier which can turn it up to 5.5V (and be adjusted by a potentiometer).
It works well and I'm quite satisfied with the performance but maybe there are some obvious faults with the design that might affect stability? Perhaps there should be a buffer somewhere in the circuit? Will R2 and R3 change value over time and cause unbalance?
I would greatly appreciate any suggestions. Thanks!