This is a 4-channel PWM sender with a passive volume controller using FSR. I made it especially for my modified cassette tape player that I posted before. Each channel has a potentiometer and a switch, so I can set different pulse width on each channel, send them to the cassette player and the cassette's motor will rotate at different speed depending the PWM this box sends.

And also I added a very simple passive volume controller using FSR. The output from the cassette player feeds into this box, and through the volume controller, now I can control the volume with FSR. It's not working linearly, so don't expect its working like a touch-sensitive pad out there. Its control range is very shallow so will be abit hard to control the volume like what you expect.

SIGNAL FLOW DIAGRAM

SCHEMATIC

STRIPBOARD LAYOUT

FRONTPANEL LAYOUT

I used Hammond 125B clone as an enclosure.

This layout is actual size, so you can use it as a drilling template. As you can see, I used mechanical keyboard switches, so it's abit hard to cut the square holes. 

Schematics: LINK

STRIPBOARD LAYOUT

I used J113 instead of 2N5457. 

CV ins and Trig ins seem to work, however 'Co-Co' side of trig in acts up. 

When powering on, it works but after a few moments, it stop working. 

No clue unfortunatley.

FACEPLATE LAYOUT