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.
ORIGINAL SCHEMATIC & OTHER INFORMATION: YUSYNTH STRIPBOARD LAYOUT 1 2 FACEPLATE LAYOUT This layout is actual size, so you can use it...
ORIGINAL SCHEMATIC & OTHER INFORMATION: birthofasynth
STRIPBOARD LAYOUT
Original circuit uses LF442 and LM394 for the exponential converter. As you know, LM394 is obsolete and LF442 is hard to find these days, so I substituted LM394 with a matched pair of 2n3904s and LF442 with TL072. I have no significant issues so far.
'SKEW MODIFICATION'
The 'Skew' does nothing until it passes 12o'clock. If the 1st pin of 'Skew' potentiometer is connected to '-3v' instead of '-12v', it starts morphing the wave once you turns the knob. So I added a simple voltage divider as you can see above.
FACEPLATE LAYOUT
The dimension is 30mm(6hp) x 129mm
7mm hole : potentiometer (6ea)
6mm hole : 3.5mm jacks (7ea)
6mm hole : DPDT On-On toggle switch (1ea)
3mm : mounting screws
MEASUREMENT
Sine wave output: 9.99Vpp
Triangle wave output: 9.55Vpp
Pulse wave output: 9.95Vpp
Frequency range: 0.35Hz ~ 20.9KHz
Skewed triangle wave
Skewed sine wave
Original schematic, BOM and information: LINK STRIPBOARD LAYOUT Three of Twin-T. Each one has different value of capacitors, normally hig...
Three of Twin-T. Each one has different value of capacitors, normally higher value you put, lower frequency you get. I ended up selecting 470nF, 100nF and 22nF, however it's worth trying different value to meet your taste. And led also changes the tone depending on its color.
All decoupling capacitors, 100nF are soldered underneath the boards.
FACEPLATE LAYOUT
6hp faceplate layout. The dimension is 30mm x 129mm.
It's actual size so you can use it as a drilling template.
Potentiometer: 7mm
3.5mm jack: 6mm
Mounting screw: 3mm
MFOS VC LFO with Sync Input Modification Schematics& BOM MFOS VC LFO : LINK Sync Input Modification : LINK STRIPBOARD LAYOUT -All dec...
-All de-coupling capacitors, 100nF, are soldered underneath the boards.
-To reduce the depth of a module, I attached the board LM13700 is placed behind other two boards by using jumper pins like the pic above, which is a little bit tricky but not that hard to do.
FACEPLATE LAYOUT
The layout is actual size so you can use it as a drilling template.
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