[sdiy] Cheap Midi->CV

[Andre Majorel]

On 2005-09-08 22:50 +0200, Simon Brouwer wrote:
> At 00:01 8-9-2005, you wrote:
>
> >I don't need a frequency counter to know when a guitar string is
> >7.3 cents off. So yes, probably.
> 
> Sure you can hear it while tuning your instrument (if my calculation
> is correct, at  e.g. 440Hz, a difference of 0.073 of a semitone would
> give a beat frequency of about 2 Hz). I wonder if you would notice the
> difference while playing, though, especially between different notes?

I notice it while playing chords. And I don't have absolute
pitch or golden ears or anything like that.

> A couple of years ago I built a MIDI2CV using an 8 bit DAC, using 4LSB 
> steps per semitone, for a range of 64 semitones (more than 5 octaves).
> I found this quite usable, not really out of tune.
> If I remember correctly, this DAC (a ZN426) had accuracy specified at
> better than 0.5 LSB which would be a factor 2 worse than a 12 bit DAC
> with 2 LSB accuracy if used for a range of 10 octaves.
> 
> So I was feeling quite comfortable choosing a 12 bit DAC for my next
> project. I am not so sure about that now...

Depends. Does it have one or several channels ?

> Would the accuracy of VCO's not be the limiting factor?

I knew someone would say that. :-)

-- 
André Majorel <amajorel at teaser.fr>
http://www.teaser.fr/~amajorel/