[sdiy] RE: Polyphonic synthesizer (controlling with vactrols)

[mikko.a.helin at nokia.com]

I've though to update DAC's (or actually the S&H stages after DAC and mux) via parallel (printer) port, another possible choice of interface is USB. I think there are some parallel multiplying DAC's that could be used here like AD7541 (or AD/MP75_something_else). Two 8-bit latches are needed, one for storing the address for mux and the other for the MSB (or LSB) for the DAC. Serial DAC's were handy but too slow with parallel port interface, maybe could work via USB (with FTDI chips or some else)? Unfortunately there aren't soundcards with variable rate outputs (to avoid aliasing like Paul suggested -actually there are some Ananlog ISA chipsets that can do it for both outputs at the same time but those soundcards are obsolete now). So you can only downpitch the wavetables and need one for each oct or so to avoid harmonic loss, and have to use interpolation (linear is ok).
-Mikko

> -----Original Message-----
> From: ext intent [mailto:intent at club-internet.fr]
> Sent: 22. April 2002 23:04
> To: Helin Mikko.A (NET/Tampere)
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] RE: Polyphonic synthesizer (controlling with
> vactrols)
> 
> 
> Le Lundi 22 Avril 2002 17:10, vous avez écrit :
> > Hi.
> > Nice synth! I've been recently playing with Linux and I'm 
> considering to
> > build a poly synth with the digital software oscillators and analog
> > filters. Seems many (incl. MiMi) are using the Moog filter 
> for VCF for
> > polyphonic synth, so it may be the one I'll use. MiMi seems 
> to use 12 bit
> > DAC's for control CV's, is it really enough (no stepping?)? 
> I think that by
> 
> Hello,
> 
> I am doing something similar, ie using Linux as the sound 
> generator to feed 
> analog filters controlled by DACs.
> 
> I don't know yet if 12 bits is enough, I use only 10 bits at 
> the moment but i 
> will try 12 soon.
> 
> BTW how do you intend to send data to the DACs ?
> 
> Linium
>