Apeks is a DIY 12-bit through-hole adaptation of Mutable Instruments Peaks. Peaks was discontinued in 2017, but it’s still pretty useful, and you can still see it in modern racks. For a starter system, it offers lots of functionality.
The module was made as a collaboration between Quinie and MiguelDeTrool.
We saw what sound-force.nl did for Braids, and noticed Peaks used the same classic STM32 processor, so the same style of conversion could be done. Overall the conversion process was very similar to what Sound Force describes in their page about Braids: the layout is the same as it leaves space for THT components, the main PCB is shorter than 100mm, and the firmware only needs to have a few files changed (dac.h, dac.cc, lfo.h, and mini_sequencer.h).
The output stage needed to be modified slightly, as Peaks’ output swing is 16V, which at 12 bits means the resolution would only be at almost 4mV. That’s almost 5 cents at 1V/Oct, which is too much, as we could hear the steps in the output.
This version uses a 12 bit DAC, and the output op-amps scale the output to +/- 5V. This allows for a resolution of around 2.44mV, which we find acceptable for non-pitch related modulation.
for more info and files please goto to MiguelDeTrool Github page