Augmentations for Casio MT65 Keyboard

[gasboss775]

I acquired a Casio MT65 "toy" keyboard as a result of my eldest daughter clearing out her room.

It's actually not bad for a toy. However I did think that it could be improved upon. So far the following circuits have only been breadboarded, but they do work.

First up, Goschillator filter circuit. .

Modulated clipper circuit.

PWM circuit

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[gasboss775]

I tried the following VCF in conjunction with the envelope follower circuit in the other circuits

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[gasboss775]

This is the support circuitry for the above VCF, thought I should post it as there were some variations from the original posted circuits in my first post.

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[gasboss775]

Yesterday I built another VCF to try with my Casio MT65 keyboard. It was based on a circuit by Eric Archer, that can be found, here:

9V Lowpass VCF

I had trouble getting his expo converter to work even with a rail to rail CMOS opamp ( lmc6482 ) Anyway I devised an alternative converter that can work with a cheap and simple lm358 with a single +12 V supply. I suspect it could work on lower but then I think a rail to rail opamp would become necessary, I try to avoid them as they are so much more expensive than regular opamp.

The circuit worked very well and actually produced some respectable sounds.

Here is the schematic of the VCF

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[PHOBoS]

ah, the good old Eric Archer LPF. I still have one laying around here which I am thinking of putting in a box with some other circuits
I have. So this thread is inspirational I build mine with a TL072 TLC2262CP and didn't encounter any problems, or at least it sounds great. I
also used an opamp for the fake GND.

Since you already have a squared up version of the signal you could put the CD4026 with an R2R in there as a suboscillator.
It would only take 1 chip and a couple of resistors (and a mixer I guess).
(in case you missed it I posted a track in which I used it here and the patch here)

[gasboss775]

[PHOBoS]

oops I took a closer look at the opamp and I actually used a TLC2262CP. It had collected some dust over
the time it has been laying around here and I only took a quick glance. Had no idea I actually used a rail-to-rail opamp.

what exactly do you mean by tracking pitch, something that isn't a squarewave ? I assume that by squaring up the signal you
pretty much have something that tracks pitch. A divider might clean it up a bit though. The 4046 can also be used as a pitch
tracker but it is mostly fun when it fails doing that correctly

[gasboss775]

[gasboss775]

I have been doing some more experimenting with this interesting old instrument ( too good to be described as just a toy IMHO. )

I have added separate outs for the drums ( analogue ) and accompaniment parts to allow for separate processing of these parts, the original output is used for the keyboard part of the instrument.

I have tried a few circuits with interesting results though I haven't got around to draughting schematics for them yet, other than scribbled on paper!

I plan on posting my schematics here once they are done,

WATCH THIS SPACE !