[sdiy] 8bits, 10bits or12bits DAC for a midi2cv converter?

[jean-pierre.desrochers at ville.quebec.qc.ca]

Thanks for the helpfull and detailed info!
JP

-----Message d'origine-----
De : m.bareille at free.fr [mailto:m.bareille at free.fr]
Envoyé : 18 octobre 2007 09:38
À : jean-pierre.desrochers at ville.quebec.qc.ca
Cc : synth-diy at dropmix.xs4all.nl
Objet : Re: [sdiy] 8bits, 10bits or12bits DAC for a midi2cv converter?


Hello,

> Seeing the posts about the paia's midi2cv8
> I was wondering what 'should' be a good DAC
> for a midi2CV output range of around 0 to 8vdc (8 octaves)?

8 bits is enough for a 10 oct range in 1V/Oct ... DAC0832  ( or
DAC0831/0830)
accuracy is good enough for normall use

> I'm thinking of building one from scratch with a PIC controller.

Please check here for 8 bits versions:

http://m.bareille.free.fr/mcv876/mcv876.html ( the big one)
http://m.bareille.free.fr/mcv628/mcv628.html  ( the small one)

and the 12 bits version of the big one for accurtate V/Hz or esotheric
scales

http://m.bareille.free.fr/mcv876/mcv876_12bits.html


> I saw PAIA's is
> using an 8 bits DAC which only will gives a 256 steps
> resolution...

there is only 128 MIDI notes so with 8 bits you  get 2 steps per notes

>For example if you need 10 steps between
> all semitones (half of a note) to get
> rid of any 'staircase' effect between notes,
> that gives 256/10steps per semitones = 25 notes span
> which is 2 octaves.. Not very usefull.
> In revenche a 10 bits DAC with the same needs
> would give (1024/10steps per semitones)/12 notes per octave
> gives more than 8 octaves.
> Am-I correct? A 10bits DAC would be more valuable?
> Do I miss something?

right, and 12 or 16 bits give even more ... Another good solution is to use
a
pair of 8 bit DACs to emulate a 16bit one ... one for coarse pitch with a
10V
range /256 steps  , the other one with a 1V range/256 steps  for fine pitch
summed with the first one. That's the method i am using to implement pitch
bend
with my MCV's on 1V/oct synths... Accurate enough, fast and cheap ...

Cheers,

Marc B.