Casio CZ/ VZ/ FZ - Pro Series

On Sat, Mar 14, 2015 at 02:30:38PM +0000, gordon@... [CZsynth] wrote:
> On Sat, Mar 14, 2015 at 07:21:18AM -0700, smw-mail@... [CZsynth] wrote:
> > I would look it up in the service manual before tweaking it. Sometimes those pots are finely tuned.
> 
> It's not that fussy.  It's just the 17kHz rolloff on the output of the DAC.
> 
> You probably won't hurt anything by fiddling with it, but you won't make a hell of a lot of difference to the sound either.  If you want an actual LPF like on an analogue synth, you'll need to go outboard :-)
> 

And on that note, if you want to build a simple outboard VCF you could do worse than to build a clone of the Steiner Synthacon filter.  Its performance is pretty horrible - it suffers badly from control voltage breakthrough on the output *and* input voltage breakthrough on the control, so its actual cutoff frequency is dependent on the input signal!  However, it has an extremely good performance-to-fiddly-bits ratio.

Here's a prototype clone I made, built "dead bug" style on a bit of scrap PCB
http://gjcp.net/~gordonjcp/filter.jpg

It sounds like this (be careful! My early version had fairly uncontrollable resonance):
http://gjcp.net/~gordonjcp/filtertest.ogg

And it has highpass and lowpass *inputs* - not outputs - so you can use it as a sort of frequency-variable crossfader, like this:
http://gjcp.net/~gordonjcp/mp3s/hilow.ogg

Here's a good writeup:
http://yusynth.net/Modular/EN/STEINERVCF/index-v2.html

-- 
Gordonjcp