Level Bypass

The Level Bypass mod allows you to have a second channel with a different level (output volume) setting. It works by shorting over the level control which gives the maximum volume available. Engage the footswitch, and the current level setting takes affect. By adjusting the level control, you can get two different settings, one with "boost" (the level bypassed) and the other "normal" (level not bypassed, using current level setting on knob.)

The Schematic Here is the schematic for the level bypass mod. It simply shorts across the level pot to create an "all out" volume level. Click on the picture to enlarge it.
STEP 1: Re-Wire The Level Pot The level pot is marked 100KL or 100KB. On my model, the three wires connecting it were light blue, orange and purple. The orange wire was the middle (wiper) one. Unsolder the wiper (middle) wire from the potentiometer. Replace it by a length of wire (black, here). Next, solder another wire (red, here) to the light-blue wire side so that both wires connect at the same point. This is the upper side of the potentiometer and marks the full-volume location.
STEP 2: Wire the Switch I used a DPDT switch, though you only need one side, so a SPDT would do just fine. Solder the orange wire (or whichever wire connected to the level's wiper pin) to the center pin of the switch. Then, wire the black and red wires above to either side of the switch. It doesn't matter which side because this is a push-button footswitch.
STEP 3: Mount the Switch Finally, as the last step for all the mods, mount the switch in the hole you drilled earlier. Here you can see the switch in the lower portion of the picture. That's it! To test, plug in to an amp and find the setting of the switch where the level (volume) knob has no effect - this is the max output. Then, lower the gain a bit for your "rhythm" sound. There you have it - 2 channel TubeScreamer!

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