Footswitch Tuner and Boost Mods

The two footswitch mods are great for live situations - the boost function is almost like having a second channel for each model. The built-in tuner can be engaged by a tap of the foot and the amp will mute while you tune up. Both of these mods are based on the same concept of grounding a pin to engage the function.

When you remove the top CPU board, you expose the underside of the lower Input board. At the front of this board are 2 multi-pin connectors. The connector on the right has the boost and tuner control. The Tuner control pin is the pin at the leftmost of this connector. It has a white wire connected to it from the other side. The second pin over is the Boost control pin. Solder one wire to each of these pins. Each wire will connect out to the footswitch jack so cut them to the correct length. Take great care not to solder the two pins together and check your work often. The Tuner and Boost control pins are logic pins. When they are pulled low (to ground, or 0V), they engage the function. So, to turn on the boost, you ground its pin. To turn off the boost, un-ground the pin. The tuner works a little differently - to switch the tuner to chromatic mode, ground the pin for more than 3 seconds. Then, lift the ground and ground it one more time to disengage the Tuner. When using the footswitch, you will hit the switch once to engage the tuner. Then, tap it 3 times in a row quickly to disengage the tuner.
Use a ground lug wire connector to create the ground wire for the switching operation. Then, screw it to the ground screw on one of the standoffs (or alternatively, take your ground from another "legal" place on the board). This ground wire, along with the two from the Tuner and Boost control pins (shown wrapping around the front here) form the 3 wire connection that will go to the 1/4" Stereo Jack. Most 2-switch controllers use this 1/4" Stereo Switching mechanism.
The ground wire connects to the ground lug of the 1/4" jack. The tuner and boost connect to the tip and ring lugs. Get these soldered in place, then add the footswitch and your mod is complete!
Here's the back plate on the re-assembled enclosure, complete with labels for the new functionality.
Here's my old home-made footswitch with 2 SPST on/off footswitches connected to a 1/4" Stereo Jack. The switches were originally used for switching industrial lamps and I got them at a surplus store.
This is the inside of the footswitch box. Each switch has 2 wires, one connects to the (common) ground lug, the others to the tip and ring lug respectively. A long stereo 1/4" cable is used to make the amp connection.
Alternatively, you can use a commercially available generic footswitch box. I picked up this one for $5 at the bargain-table at a local music store.

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