[sdiy] Digital control

[Ray Wilson]

Hi Johannes

Check out all of these sites (including mine)
http://www.musicfromouterspace.com/analogsynth/synthdiy_links.html

Welcome to synth-diy

Ray


----- Original Message ----- 
From: "Johannes Öberg" <johannes.oberg at gmail.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, February 27, 2005 7:34 PM
Subject: Re: [sdiy] Digital control


> Thanks for your help guys!
>
> Are the Mbase01 schematics available somewhere, or does anybody know
> how they implemented the DCR's? How did the Polysix or other early
> patchmemory synths do it?
>
> The digital resistor chips are to expensive for me unfortunately. If I
> would try to build a digitally controlled analog synth (of course,
> this is more like dreaming than considering) I would need alot of
> digitially controlled "pots". What's the _cheapest_ way of doing this
> with an acceptable reproducability and resolution (say at least 6
> bits) ? IIRC the old polysynths used to use a single D/A going into
> these crazy mega-sample'n'hold chips, going into VCR's. Are these
> SnH's still an alternative? Can't it be done in a simpler way, if one
> accepts poorer stability or something?
>
> The other alternative seems to be multiplying DAC's, but this can't be
> a cost-effective way of doing it, can it? Or did I misunderstand? I'm
> believing you mean that I should use one DAC per pot. It sure seems
> compellingly simple enough though.
>
> Shouldn't it be possible to use a totally el-cheapo method, something
> like a single transistor as the VCR and either a giant sample'n'hold
> thing or perhaps even the old one-bit-D/A from the microcontroller? Or
> am I totally naive? Any linearity problems could be compensated for in
> software, methinks. As most of the 'digitally controlled resistors'
> would replace pots for non-timecritical stuff (like Attack rates) slow
> settling time (or what it's called) due to slow samplerate for the D/A
> wouldn't be a problem.
>
> /Johannes