[sdiy] MIDI-CV convertor idea

[Mike Beauchamp]

> HOWEVER…a passive mix doesn’t use a virtual ground node, so there’s the 
> potential for bleed through from one channel to another. So I did a 
> quick simulation of the situation to see if this was a problem, shown 
> attached. U1 takes a 0-4V signal from the Bend DAC and turns it into a 
> +/-83mV signal. This is then fed to both mixers. The other mix input 
> comes from the appropriate Note DAC, also 0-4V. Each mixer is then 
> followed by x4 make-up gain, which compensates fro the /2 loss in the 
> mixer and adds an extra x2 to turn the Note CV range into 0-8V and the 
> pitch bend range into the standard +/-2 semitones.

Just wanted to say that pitch bend range isn't standardized to +/- 2 
semitones, although that is a lot of synthesizers' default setting. The 
MIDI spec says that it is variable and reconfigurable to +/- 24 
semitones and optionally adjustable by cents. Some other makers of 
continuous pitch instruments require even larger ranges, and I think 
this is called for in the MPE spec as well.

Mike