Sub-octave generator and Ring modulator
This is a relatively simple project, even if the logic circuits make the stripboard a bit of a mess. It's a combined sub-octave generator and ring modulator. The sub-octave generator accepts any input signal and outputs a square wave one respectively two octaves below the input freqeuncy. The ring modulator accepts any input signals (X and Y) and outputs a square wave with a frequency that is the sum and the difference (X*Y) of the two input signals.
Unfortunately there are no building instructions for this module, but at least you'll find the schematic, some photos, and some comments.
The module during prototyping.
The finished module mounted in the modular.
There are two trim potentiometers for each output. The one between the inverting input and the output of the opamp is to set the amplification to adjust the output level to match the input level. The trim potentiometer at the noninverting input are to remove the DC offset of the output signal.
Here's a demo of the sub-octave, the ASM1-VCO feeding a sawtooth to the sub-octave generator. The output from the sub-octave is a square wave with 50% duty cycle.
Here's a demo of the ring modulator, fed with a sine wave from Doepfer A-110 (which is also mixed in the beginning) as well as a square wave from the ASM-1 VCO.
It could be nice to add different mixing options to blend the original sounds with the outputs from the sub-octave generator and/or the ring modulator. However to be able to squeeze this module in a 4HE eurorack I chose to skip this, instead I'll do this with other extension modules like multiples and mixers.
That's it! Have fun and happy modulating!