Tempco Source/Analog vs Digital DIY

[Fraser, Colin J]

> -----Original Message-----
> From: Paul Perry [mailto:pfperry at melbpc.org.au]
> Sent: Wednesday, May 13, 1998 7:44 AM
> To: synth-diy at mailhost.bpa.nl
> Subject: Re: Tempco Source/Analog vs Digital DIY
> 
> 
> At 11:55 PM 12/05/98 +0000,Kyle Jarger jkjelec wrote:
> 
> >>BTW. Isn't tempco's something that you Kyle use in Hz/V adapters to
> >>you MIDI stuff or do you do it pre-D/A?
> >
> >Ummm,  I hope I'm not going to have to turn in my 
> >membership card to synth-DIY for saying this but,
> >
> >after looking at the pros and cons, we chose to do the Hz/V 
> >digitally...<duck>   ;  )
> >
> ....and so did I..
> you need at least 12 bits, I actually used 16 so the
> ptchbend wasn't lumpy
> 
I used 12 bits for hz/v on my homemade convertors, but didn't include
pitch bend so I didn't need the extra resolution.
What I'm thinking about now is a digital exponential convertor for vcos.
Has anyone tried something along the lines of a linear input to an a-d
convertor driving a rom with a lookup table for exponentiation, the
output of which drives a d-a convertor, all clocked at audio rates to
allow audio fm ?
Would this give me a temperature stable linear to exponential convertor
without having to buy 1000 tempcos ?

Colin f