I created the circuit in this schematic on protoboard, schamatic

and the code, https://github.com/elkayem/midi2cv

I use a dual opamp and a single dac, because i only need note and velocity. The opto i use is, H11L1

It works but has a strange issue that i can not figure out.

The author says the code supports midi notes from 21 to 108.

When I send midi notes to test the device,

(Arduino powered with +12, TL082 Opamp powered with +15 to GND )

The notes <= 36 gives +15V in the output of the opamp. The note 37 gives +3.43V The note 38 gives +1.7V . . .then it increments as expected until note 108 which gives +7.52 V

Also to add I have +1.5V DC offset on the both outputs of the opamp. (This, i can live with but i would love it not to happen. )

I would be very happy if you help me on this, thank you.

  • Find out what voltages are output by the DAC, and what voltages the opamp can handle. – CL. Jan 5 at 22:02

I changed the opamp to LM358 and all problems solved it works perfectly!

If you have enough motivation and time please explain me why, but i will research and learn anyway.

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