[sdiy] MIDI-CV convertor idea

[Mike Beauchamp]

> Yes, I understood that it’s not standardised. I think it might have begun as a General MIDI default, and it seems to be used as a “typical” value. Obviously most MIDI synths can respond to pitch bend messages however they see fit, so it’s very flexible. A 1V/Oct analogue synth doesn’t have quite the same flexibility! It will just respond to whatever voltage you feed it, and you can’t easily change that without knocking out the whole tuning. It’s true that my current design doesn’t easily allow the addition of a “Pitch bend range” parameter. Perhaps I’ll look at that again and see what I think about it.
> 

Wouldn't the expected behavior of the pitch bend CV output be a bipolar 
voltage centred at 0V (so nothing gets knocked out of tune when the 
range changes) and scaled appropriately for 1Voct to match the set bend 
range?

The pitch bend range would just be handled software, with your DAC 
output scaled and offset appropriately to stay centred at 0C and able to 
achieve at least +/-2V to match the MIDI spec (or even +/-4V if you want 
to make the MPE people happy). Smaller pitch bend ranges would just be 
less voltage change out of your DAC, no external scaling switching required.

Mike