hi everyone, I'm new to the forum, please excuse me if I missed some post while searching for a solution to my problem. I'll start explaining my setup right now: I was trying to build something that is conceptually the same as Salt (project that I discovered today browsing the blog and the forum) but with a different target in terms of voltages (much more like the previous Bela + Doepfer Dark Energy demo). my project aims to be a versatile CV controller for a Moog synthesizer, more specifically a Minimoog model D reissue, which accepts five 0-5V inputs.
the project is fairly simple hardware-wise, as I'm not that much experienced with electronics, so I started working with Bela which seems to be the right choice and put all my efforts in the software part.
so, to put it straight, I have six linear pots which have the central pin wired to analog inputs, left pin wired to ground and right pin wired to 3.3v (P9-03), one push button n-c wired to a gpio input and 3.3v, one 3-positions switch wired to gpios and 3.3v, five leds with a 470 Ohm resistor each wired to gpios (all gpios are from P8-07 to P8-12, P8-15 and P8-16) and five stereo jacks with the tips wired to analog outputs and one has ring wired to an analog input. all the grounds are wired together to P9-01.
with this setup and a midi interface I would like to control the five exposed CV inputs of the Minimoog, which are V-Trigger, Mod Source (which outputs the Moog random generator signal on the ring channel), Cutoff frequency, Oscillator pitch and Amplifier level.
the code i wrote up to now can be found at https://github.com/mellotanica/bela_minimoog_controller, it seems to run correctly, but i get a strange noise on the output jacks, which is a problem only for amplifier level control. the other parameters on the synth does not seem to be affected (at least audibly), but if I modulate or even throw a straight signal to the Amplifier level, i get a noise that seems like a mix of digital interference and ground noise to me.
until now i did not manage to connect an oscilloscope to the board while plugged into the synth, but i got to see the signal with the jacks unplugged. I noticed that driving the signal to 5 volts produced some distortion and a simple sine signal is flattened at the top with an evident noisy signal, while if I limit the output to say 90%, the sine seems quite clean, but this doesn't solve my problem when I listen to the synth output.
I already tried different powering solutions, I was first powering the board from my computer, then I used some usb power supplies (5v/2.4A) and a power bank (hoping to get a clean and stable source), but the problem still remains.
is there anything I should try?