Microcontroller-based VCO/VCLFO (4HP)
2 in stock.
THIS MODULE IS END-OF-LINE - there will be no more produced once this run is sold out. An updated version is planned for later in 2021.
If you want an all-singing, all-dancing VCO with super-mega-accurate tracking, lots of bells, whistles and foghorns well, there are plenty of them on the market so feel free to go take a look at them. However, if you want something simple and hackable which also happens to make a noise then we've got you covered.
Analogue VCO cores are a pain to build so this is based around a microcontroller instead - cheating? Maybe so, but it's pretty versatile and if you have the knowledge to program microcontrollers then you can hack it to your heart's content.
As supplied, the module can provide six different output waveforms: sine, triangle, square, sawtooth, something pulse-ish and digital noise - waveform selection is performed via the 'Wave' pot. If you want to get down and dirty with the code then you could easily replace the wavetables with something else.
It'll track 1V/octave pretty well over 5 octaves, this being governed by the fact that microcontrollers tend to get a bit upset if you feed more than 5V to their input pins.
Note that I say pretty well - the microcontroller has a 10-bit ADC which places a pretty hard limit on how accurately it can sense the CV. 10 bit resolution gives us 1024 'divisions' over a 5V range, meaning that each 'division' equates to around 4mV - not much, but if accurate-to-the-cent tuning is what you're after then this probably isn't the droid you're looking for.
The firmware source has a permissive license, so feel free to hack on it - updates and modifications are most welcome; my C-fu is definitely a bit rusty, and my language of choice (Go) doesn't fully support AVRs yet.
The microcontroller VCO core is present and correct, and it uses some tried and tested code to track 1V/octave over about 5 octaves. However, there's now a dedicated fine-tune control and the waveform is no longer voltage controlled.
Not only that, but there's also a range switch which allows you to use the module as either a 'regular' VCO with a range starting at C1 (~32Hz) or something more akin to an LFO, again with a range of around 5 octaves and 1V/oct scaling.
The output waveform is a filtered PWM signal - the output filter has a cutoff frequency of 1.6kHz which gives you a usable range of 5 octaves - it's a lot cheaper than a DAC.
Supplied with a panel fabricated from 1.6mm FR4 (PCB material) - mounting hardware and a power cable are also supplied.
CURRENT DRAW (approx.): ~25mA (+12). Does not use -12V.