Chuck D. Bones
Circuit Wizard
This is my attempt to replicate the Catalinbread Karma Suture using the Percolation Station (Harmonic Precolator) board. Catalinbread offers some tantalizing clues in their adverts as to what they did to create the Karma Suture from the Harmonic Percolator. I have not been able to find a Karma Suture schematic, and so far, I've been too cheap to buy a KS to trace myself. So this is my best guess. The KS adds two knobs: DIODES and DENSITY. I put my own spin on it and added a diode switch. With DIODES and DENSITY dimed and the DIODE switch set to GE, it's a stock HP.
The DENSITY control rolls back the bass at the input, which has a huge influence on the tone. I replaced C2 with a 3.3nF cap and then wired a C100K and 47nF cap in series and connected that in parallel with C2. I put the DENSITY pot, and two caps on a little Vero board.
The DIODES control is simply a C50K pot connected in series with the clipping diodes. When DIODES is turned down, the clipping diodes have less and less effect on the tone. Volume increases, distortion and compression decrease. For fun, I wired in a SPDT on-off-on switch to select between Ge diodes, LEDs or Si diodes. I also increased the BALANCE (Volume) pot from A50K to A100K so there's a little more signal available to push the diodes. I used red LEDs and 1N4743A zeners for the Si diodes. The zeners are wired in parallel, so they only conduct in the forward direction. Zeners tend to have a larger forward drop, that's why I chose them. Any Si diode will work, such as 1N4148. I left the diodes and R5 off of the PCB and put the diodes, R5 and DIODES pot on a little Vero board. It would have been neater, but the LEDs were thrown on as an afterthought. The LEDs are pretty subtle; you have to crank the HARMONICS, DENSITY and DIODES controls for the LEDs to do anything.
If you set DIODES and DENSITY to zero, BALANCE to max, and use HARMONICS as a Boost control, it makes a decent treble booster.
Here's the schematic and some pix. I went with side-mounted jacks so I'd have room for the Vero boards. Top-mounted jacks would probably have fit, but I wanted easy access to the two new pots and Vero boards. As you can see, it's a very snug fit between the jacks and the stomp switch. I had to grind the jacks down a bit and mount the stomp switch rotated 90 deg. I recommend socketing both transistors because this pedal's tone is very sensitive to the transistors. Lower hFE gives less compression and more headroom. I currently have a Russian P28 and 2N2222A installed. One day, I'll paint and label the box. The controls layout is the same as the KS.
And here it is painted and labeled (finally!). I went with the KS control names.
The DENSITY control rolls back the bass at the input, which has a huge influence on the tone. I replaced C2 with a 3.3nF cap and then wired a C100K and 47nF cap in series and connected that in parallel with C2. I put the DENSITY pot, and two caps on a little Vero board.
The DIODES control is simply a C50K pot connected in series with the clipping diodes. When DIODES is turned down, the clipping diodes have less and less effect on the tone. Volume increases, distortion and compression decrease. For fun, I wired in a SPDT on-off-on switch to select between Ge diodes, LEDs or Si diodes. I also increased the BALANCE (Volume) pot from A50K to A100K so there's a little more signal available to push the diodes. I used red LEDs and 1N4743A zeners for the Si diodes. The zeners are wired in parallel, so they only conduct in the forward direction. Zeners tend to have a larger forward drop, that's why I chose them. Any Si diode will work, such as 1N4148. I left the diodes and R5 off of the PCB and put the diodes, R5 and DIODES pot on a little Vero board. It would have been neater, but the LEDs were thrown on as an afterthought. The LEDs are pretty subtle; you have to crank the HARMONICS, DENSITY and DIODES controls for the LEDs to do anything.
If you set DIODES and DENSITY to zero, BALANCE to max, and use HARMONICS as a Boost control, it makes a decent treble booster.
Here's the schematic and some pix. I went with side-mounted jacks so I'd have room for the Vero boards. Top-mounted jacks would probably have fit, but I wanted easy access to the two new pots and Vero boards. As you can see, it's a very snug fit between the jacks and the stomp switch. I had to grind the jacks down a bit and mount the stomp switch rotated 90 deg. I recommend socketing both transistors because this pedal's tone is very sensitive to the transistors. Lower hFE gives less compression and more headroom. I currently have a Russian P28 and 2N2222A installed. One day, I'll paint and label the box. The controls layout is the same as the KS.
And here it is painted and labeled (finally!). I went with the KS control names.
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