DAC resolution

[Fraser, Colin J]

> -----Original Message-----
> From: Terry Michaels [mailto:104065.2340 at compuserve.com]
> Sent: Tuesday, March 09, 1999 6:34 PM
> To: Fraser, Colin J; synth
> Subject: RE: DAC resolution
> 
> This whole issue is based on the real world capabilities of 
> DACs and the
> way they are made.  The point I'm trying to make is you will 
> always get
> better results with a 12 bit DAC, for not a lot of extra expense.
> 
> I didn't mean to say your doing this wrong, it looks like 8 
> bit DACs seem
> to work for you just fine for you.  I guess it is more 
> correct to say I
> would use a 12 bit DAC to generate control voltages if I were 
> doing this,
> mainly because I would worry much less about pitch accuracy, 
> for a minimal
> increase in parts cost.

I guess in the end it will always come down to cost, especially where
engineers are involved ;-)

Just to confirm I wasn't kidding myself, I did a check tonight on the
voltage outputs of my cv convertor.
It uses a ZN558 8 bit converter, scaled so that the LSB gives a semitone
step.
The biggest deviation I get from the ideal voltage for any note is 1.56%,
the average error 0.68%
This is more than satisfactory as far as I'm concerned - but maybe I've been
very lucky (I've used at least 4 of these devices).
I mp3'd a wav file of some octaves and notes played simultaneously on a Juno
106 and a Pro 1 via my convertor and stuck it on my web site (
http://www.octavo.demon.co.uk/colinf/8bit.mp3 )

So as a final point - you're probably better off with a 12 bit converter if
you can find one for little more than an 8 bit, but excellent results are
entirely possible with an 8 bit converter. Also, you are likely to piss
constructors of 8-bit cv converters off if you dismiss them as toys ;-)

Colin f