DAC

Transposer/Sequencer

This module generates 1V/octave CV by summing together different intervals (12ths of a volt) via a simple Digital to Analogue Converter circuit.
The resistor values in the digital to analogue converter are weighted to generate reasonably accurate V/oct control voltages.
(*I wouldn't dare call this design 'precise' unless you sub in a fancy opamp for U5 and add a bunch more trimmers)
The 'digital' inputs are actually analogue comparators that convert any synthesiser signal that crosses 1V into an either 'ON' or 'OFF' state. There are no microcontrollers or dedicated ADC or DAC chips involved.
The +12 input adds 12 semitones, or 1V. +1 input adds 1 semitone, ~83.33mV.
The inputs add together so if +5, +4 are active at the same time the output will be 9 semitones of CV (750mV).
All inputs active gives 2.5833V, 31 semitones above 0V. This gives DAC the range of a small keyboard, but much trickier to play. Getting the right combination of active inputs sequentially to play a specific melody could well be prohibitively complicated. On the other hand, feeding it clock/LFO signals from all over your synthesiser will probably result in nonsensical phrases you'd have never have thought of on your own.
Playing it safe with a clock divider and just the top three or four inputs should result in pleasant arpeggiator-esque sequences.
The inputs for activating each interval can be gates or any other signal >1V.
With a switch down, signal applied to the input will add that interval to the output.
With the switch up the logic is inverted (like a 'NOT' logic gate) and the interval will be added when the input is less than 1V. A gate or +ve voltage will turn it off.
With no signal plugged in you can use the switches as a manual ON/OFF for each interval.
The bottom input IN is summed with the generated CV so the module can be used to transpose up the output of a sequencer, keyboard, or anything else you want to shove in there.
Since DAC only generates positive voltages, negative transposing can only be achieved by tuning your VCO with desired intervals active, then deactivating them to transpose downwards.

https://isaacbeers.square.site/product/dac/1