Hello,
I have Casio SA 20 witch I want to use with my future eurorack. I want to make some mods according to the drawings(http://synthvibrations.com/tag/casio-sa/):
But I have one more idea - may I add input for external oscilator? I think just to add mono-jack input into the pitchshift line witch proper switch that will cut factory crystal. Is it so simple or do I need any normalization of signal before?
Any other ideas for the mods, maybe adding some expression stuff like vibrato? But how : D
Flagging @fredrik, @Dud and @antoine.pasde2 to get their attention for this (they’d be the experts for this.) I don’t think that you’d want to cut the crystal off though-chances are that’s more for controlling a microprocessor than for audio oscillation-but you might still be able to get glitchy with it-maybe that’s what you want.
I’m no circuit bending expert, but it looks like you need a clock in the 6 to 22MHz range, for the circuit to work reasonably.
A direct external clock input at those frequencies might be a bit hard to obtain ( it could also cause interference to nearby radio equipment if connected with an un-shielded audio cable ).
I think what circuit benders often do is to install a controllable high speed oscillator.
Sam mentioned one a couple of times in his videos (maybe the LTC1799 with a vactrol for VC input?)
I know I shouldn’t do this but I’ll point you to this article that I haven’t read but seems to describe something you could use.
If it’s circuits is anything like an sk-1, LTC1799 is the way to go, as with most Casio
Keyboards.
I would imagine their crystal is similar, and with mine, I cut the original trace and routed it to the LTC with 2 switches, a pitch pot, and external jumpers.
for tremolo/vibrato/LFO, a little 555 timer with a vactrol on the pitch pot (for internal LFO) or just a vactrol with maybe a pot (Attenuator) with a jack socket for external control
Thanks! Still waiting for the LTC1799, will back to it then I will have all parts. Your SA looks mad, do you have any jamm records using your modular with this beast?
For sure I will have some more detailed question when I will try to put mine together.
I`m curious if there is any easy way to implement pot as an modulation knob for your LFO scheme, or maybe there is already some cheap pre-made parts for it. Like this springy one -
EDIT: Just found this springy thing in my basement. Need to figure out how the pinout is and if it is close to 10k - this as I assume it will fit into your LFO drawing? Or it will be more complicated? For the plastic part I can find someone with 3d printer and model it.
Forum cut the image - you gave to click it to see 5 pins.
