Polyphonic MIDI to CV?

DIY STUFF
21

Hi Bitnik, Lu.caas and others,

it is 3/4 of a year later, but I am very much interested in this topic.
I do not find too much on it, but some things here and there. Most of them do not really finish off.
I found this one: How many bits are needed for CV DAC? - MUFF WIGGLER

For pitch it seems mandatory to have at least 16 bits so then one could use a bunch of 4 channel DACs like mentioned there: the AD5686
or something from TI: https://www.ti.com/lit/ds/symlink/dac80508.pdf under $10.

But multiplexing / demultiplexing + sample and hold seems interesting, except that the quad sample and hold chips seem about as expensive as the DACs or more expensive: 12 euro for quad, 18 for octal.

That would only make sense for more than 16 bits resolution, right?

If I’d split the outputs in pitch and other CV then this MAX11300 chip could be interesting,
a 12-bit, 20 channel DAC.

To be honest, I’d like to try and have at least 4 but rather 8 or 12 voice polyphony, so then it adds up.

Something else would be how to manage tuning the oscillators… You would have to write a routine, feeding back the signal of the VCO to the module and have the Arduino deduct the frequency in some way.

And Lu.caas: how did you manage, meanwhile? Were 12 bits sufficient for pitch?

2 Likes
22

Seems overkill. 12 bits is probably adequate for all but the most demanding listeners and situations. 16 bits over 10 octaves gives (ideally) 0.2 cents resolution and I can’t think of any reason why you’d need even that much let alone more.

3 Likes
23

yeah most of us do not have ears that hear better than 12 bit .

2 Likes
24

Mine must not even be 8 bits :slight_smile:

2 Likes
25

Resistor ladder DAC you know :rofl:

1 Like
26

I can’t really help you with that! I think I will do my research for you and I’ll get back to you :blush:

And yeah 12 bits DAC is way way suffisant if you use the standard 1v per octave, do not worry about this. I use a MCP4822 (but on a monophonic synth :sweat_smile:) and it outputs 500mV per octave that’s being doubled by an opamp. It sounds really tuned it’s okay.

1 Like
27

I recently found Bastl 1983 Eurorack Module – Polyphonic MIDI to CV Interface
Which does exactly this, if I understand correctly. Most of bastl instruments are open source, but for this one I could not find schematics. But the code here

Looks like it can do the automatic tuning. :slight_smile:

1 Like