CONTEST Buddy's Contest

[edit: typo on sheet 2 corrected]

Here's the schematic. It's mono in, stereo out. It's possible to put the spare opamp to work as a 2nd input buffer and wire it for true stereo. I had to draw the line somewhere due to the 125B box restriction. If I went stereo in, stereo out, I'd use a 1590BB box so I could install four jacks for maximum flexibility. The BLEND control goes from Clean to Vibrato with Chorus in between. The SHAPE switch selects a smoothed triangle or random ramp waveform. The smoothed triangle requires the cb mod to the STOMPLFO chip. Or you can change R60 to select sine or triangle if you're running the stock STOMPLFO chip. The breadboard pic is not 100% accurate because I changed from a single to a dual pot for BLEND.
It's snug, but it will fit in a 125B. Not shown on the schematic is the outboard wiring.
I'll post a full circuit description in The Boneyard.

Stereo Chorus v0.5 sheet 1.png

Stereo Chorus v0.5 sheet 2.png
 
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Awesome! Can’t wait to try this out (just the stock stomplfo unfortunately)

What do you think of separating the dual gang blend control for more control over the stereo image? I’ll definitely do that when I try it in true stereo, but I wonder if it would give interesting results on the mono in as well— could allow for pseudo-Eventide style chorusing.
 
That's a great platform for mods.
You might want to check out my mods here for some ideas. Keep in mind that even with matched diodes, the clipping is asymmetric because Q2 and R5 drive the diodes asymmetrically.
 
Make sure those 3-terminal blocks are secure. I had a solder joint crack on one of mine. I don't like socketing charge pumps, but in this case it might be a good idea. Not all circuits need the -9V and +18V and that 40KHz noise generator is running all of the time. At least with a socket, you have the option of pulling the charge pump out when you don't need it.
 
Bricksnbeatles said:
What do you think of separating the dual gang blend control for more control over the stereo image? I’ll definitely do that when I try it in true stereo, but I wonder if it would give interesting results on the mono in as well— could allow for pseudo-Eventide style chorusing.
Click to expand...
I tried separate BLEND controls with mono-in, stereo-out and it does allow for some additional tailoring of the stereo image.
 
BuddytheReow said:
One week down. Get those breadboards going!
Click to expand...

Nah, I already modded an existing board set for proof of concept, built a working model, designed a new board with the needed mods, and ordered five new boards just now. The original boards were already "my" design to begin with. I think this project is going to be a bit simpler that what I posted upthread (which I still plan on doing too eventually), but my first test build sounds pretty danged good already. Tentative format is now variable HPF, boost/cut bass, variable resonance variable frequency LPF.
 
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Yeah, me too!

My latest entry: A Slightly Dirty Boost. All components are available from the usual sources. Mouser sells the 4N35 opto-couplers. At low GAIN settings it plays clean. As you turn up the GAIN, the lower harmonics come on very gradually until you overdrive the opto-coupler. Clipping is fairly symmetric and the note decay is very smooth. With GAIN at noon or below, the freq response is flat. At higher GAIN settings, the low bass rolls off a bit. The circuit is not complicated, but the operation is a little out of the ordinary. This circuit exploits the non-linear relationship between LED current (U2A) and phototransistor current (U2B). I've been trying to get a circuit like this to work the way I wanted for quite some time. That fact is reflected in the rev number. D1 can be any color LED you like. It lights up when the optocoupler saturates and can bse used as an overdrive indicator. In the pic below, D1 is a 3mm red superbright and it's lit because I'm driving the opto to saturation. NB: I have changed a few resistor values since I shot that breadboard photo.

Opto-Boost sch v6.0.png

Opto-Boost v6.0 breadboard 02.jpg
 
Chuck D. Bones said:
Yeah, me too!

My latest entry: A Slightly Dirty Boost. All components are available from the usual sources. Mouser sells the 4N35 opto-couplers. At low GAIN settings it plays clean. As you turn up the GAIN, the lower harmonics come on very gradually until you overdrive the opto-coupler. Clipping is fairly symmetric and the note decay is very smooth. With GAIN at noon or below, the freq response is flat. At higher GAIN settings, the low bass rolls off a bit. The circuit is not complicated, but the operation is a little out of the ordinary. This circuit exploits the non-linear relationship between LED current (U2A) and phototransistor current (U2B). I've been trying to get a circuit like this to work the way I wanted for quite some time. That fact is reflected in the rev number. D1 can be any color LED you like. It lights up when the optocoupler saturates and can bse used as an overdrive indicator. In the pic below, D1 is a 3mm red superbright and it's lit because I'm driving the opto to saturation. NB: I have changed a few resistor values since I shot that breadboard photo.

View attachment 40944

View attachment 40945
Click to expand...
That’s awesome. Very clever too!
 
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