[sdiy] MIDM-CV DACs, Part #3 (last)

[Chris Crosskey]

Paul is wel;l known for hius obsession with accuracy and I admit I have to
agree with him on this...you can always introduce errors and noise if you
want it, but it's almost impossible to take away if you don't....better to
go for rather retentive specs on this sort of thing methinks....

chrisc

> -----Original Message-----
> From: Colin Fraser [mailto:colin at colinfraser.com]
> Sent: 19 September 2002 08:39
> To: synth-diy at dropmix.xs4all.nl; jorgen.bergfors at idg.se
> Subject: Re: [sdiy] MIDM-CV DACs, Part #3 (last)
> 
> 
> ----- Original Message -----
> From: <jorgen.bergfors at idg.se>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, September 19, 2002 7:39 AM
> Subject: Re: [sdiy] MIDM-CV DACs, Part #3 (last)
> 
> 
> >
> > Although this theoretical discussion probably is correct, 
> in reality a 12
> > bit DAC is more than enough.
> > I have built the Oakley MidiDAC, which I believe is based 
> on a 12 bit DAC.
> > I have measured every single midi note value with a 4 1/2 
> digit DVM. The
> > accurracy is way better than you could dream of tuning a 
> piano or guitar,
> > for instance.
> 
> Paul S dictates authoritatively that you need your DAC to 
> have an error of
> less than 1% of a semitone.
> Assume you have 1 oscillator tuned to 256Hz (2 ^ 8)
> We want a second oscillator at the same frequency, but, oh no 
> !, we have a 1
> cent error !
> Our actual frequency is 2 ^ 8.000833 = 256.148 Hz.
> So we have a beat frequency of 0.148 Hz - that's about one 
> beat every 7
> seconds.
> Wait a minute - at maximum DAC error, my synth sounds better 
> ! (assuming my
> oscs don't soft sync that close)
> That can't be right !
> 
> Colin f
> 
> 
> 

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