Under the expression pedal is a hard rubber pad that touches the body of the GT-3 unit when you push it all the way forward. The basic idea of this modification is to pack this pad up with something spongy, like part of an old neoprene mouse pad. Once the mouse pad piece is attached you will have to push the pedal with more force to get to the higher ranges of the pedal.

Because you will have to press much harder to get to the upper ranges of the expression pedal you can use that range as an assigned switch in the GT-3.

The rubber stopper that is under the foot pedal of the GT-3 is 4 x 2 centimetres. To pack up this pad with some mouse pad cut a rectangular piece the same size. Apply super glue to the foam side of the cut mouse pad and attach to the GT-3 stopper. (Make sure you have the material covered side of the mouse pad on the bottom). When you have the mouse pad aligned leave it for a few minutes to dry.

Settings to use the switch on your expression pedal.

Please note ! : Now that you have this packed piece of mouse pad under your expression pedal all your previous settings may need tweaking. The range of the pedal has been reduced so if your patches have the expression pedal as a volume controller you'll have to adjust them to suit your new switchable expression pedal.

To adjust your old setting you will have to disable all patches that use the first part of the Pedal/Assign that says : EXP Pedal. The reason for this is that you cant assign a pedal range to this position you can only say whether it's on or off.

To disable the EXP Pedal just set it to OFF.

To use the Expression pedal for any patch or effect you'll need to use the Assign positions of the GT-3. There are 8 positions you can use to assign effects to the expression pedal, and all of them can be used to set the Expression pedal's range as we now need.

To set the Expression pedal as a switchable on/off Wah pedal use the following settings :


ASSIGN 1
Target: WAH: On/Off
Target Min: Off
Target Max: On
Source: EXP PEDAL
Source Mode: Toggle
Active Range Low: 126
Active Range High: 127


ASSIGN 2
Target: WAH: Pedal
Target Min: 0
Target Max: 100
Source: EXP PEDAL
Source Mode: Normal
Active Range Low: 0
Active Range High: 75

In the Assign 1 position the switch will operate if you move the pedal into the range from 126-127. This position on the pedal is right at the end of the forward movement of the expression pedal.

In the Assign 2 position the pedal will operate in the range from 0-75. The reason it doesn't go from 0-126 is because you would be switching the WAH on and off all the time. Also my mouse pad piece that I used on my GT-3 is very thick.
NOTE : If you had a thinner mouse pad piece or a lighter touch with your foot you could increase the operating range of the wah from 0-75 to 0-100 or even higher. I suggest you experiment and see what suits you.

Ok so now that you have the WAH assigned you should be able to play as you used to but now when you want the WAH effect to come on all you have to do is press down hard with your toe and the WAH should come on. To switch it off you just have to press down hard again.

With any luck you shouldn't hear the WAH click on like you do with a Crybaby WAH because the switch is truly a digital one. This switch wont fail unless the mouse pad piece falls off !.

Once you have this notion burnt into your brain you should be able to see that pretty much any effect can be set up to switch on and off with the Expression pedal.

Have fun !.