multiple-type Digisound VCDO thing?

[David Halliday (Volt Computer)]

I am not familiar with the circuit but...

I am asuming that you are taking a VC oscillator, running it through
some kind of address generator and clocking address lines of an EPROM -
you have waveshapes loaded in EPROM which are D/A'd and sent out.


Just off the top of my head, you could probably run an adder circuit
between the address lines - cycle the other adder input with a slowly
varying input from a VC Digital Low Freq Osc...  This would give you a
varying phase shift between the two ( or more ) signals... 

You could carry this even further by having the DLFO clock another EPROM
with various vaveshapes in it...


Another thing is that you could use a much bigger EPROM and manually
switch the upper address bits to select different waveshapes.



> -----Original Message-----
> From:	WeAreAs1 at aol.com [SMTP:WeAreAs1 at aol.com]
> Sent:	Monday, April 28, 1997 10:29 AM
> To:	synth-diy at horus.sara.nl
> Cc:	brandt at fishes.ultra.net
> Subject:	Re: multiple-type Digisound VCDO thing?
> 
> Josh Brandt wrote:
> 
> << So, I was showing the Digisound VCDO schematic to a friend of mine,
> and we
> were talking things to do with it...
> 
> Our ideas-- take the output from IC3b (where it goes into IC4) and
> duplicate
> (or triplicate or quadruplicate) all of the digital circuitry, sending
> the
> same signal from IC3b and running it into 2-4 IC4's, each of which is
> connected its own IC9 (the ROM), and so on... Include separate sets of
> front
> panel controls for each set of digital circuitry, and you can
> individually
> select different waveforms for each one (or the same waveforms for
> each one,
> for that matter), and you've got multiple digital sources, all
> tracking the
> same CV. Burn a few more EPROMs, with the same (or different!) waves,
> and
> you've got a nice big flexible module _without_ having to dig up
> several
> CEM3340's. (It seems that making them paired-- one 3340 driving two
> sets of
> digital circuitry-- would be the most expedient.) 
> 
> Does this seem a reasonable idea? Am I missing some basic concept
> here? >>
> 
> Of course it's a workable idea, and yes, you'd save a bit of money on
> the
> clocking VCO, but all of your waves would always be exactly locked in
> phase
> with each other.  You wouldn't be able to detune your oscillators or
> tune
> them to different intervals.  As anyone who has played with a Korg
> DW8000/EX8000 (or a Wave PPG) already knows, detuned digital wavetable
> oscillators sound *great*.  I'd rather spend the extra $15 - $20 and
> have
> more tuning flexibility.
> 
>