For those of you who get frustrated having to decide which 2 modes you'll be able to use on your Sustainor, or have had to purchase TWO Sustainors in order to be able to use all 4 of the modes, here's some great news!! This simple mod will allow you to access ALL 4 MODES of the Sustainor by adding a few parts and an extra footswitch. And the best part of this mod is that it doesn't affect ANY of the audio circuit path!! It's strictly a control logic mod. And for those of you who hate to cut traces, there's only one trace that has to be cut. How much easier does it get???

Now some of you may be wondering what you'll be giving up. The answer is NOTHING! I left the front Channel Mode Switches fully functional. That way, regardless of whether or not you have the extra jack in use, you can still change the modes just as you normally would. Of course if you ARE using the extra jack, then you would set Channel 1 to Edge, and Channel 2 to Distortion. When the Extra jack is activated, Channel 1 becomes Clean 1, and Channel 2 is Clean 2. I did that because Edge and Distortion can sound similar, depending on how you have it set up. By using the switches for those 2 modes, it's easier to tell which one you are set to.

As mentioned, you'll note that there's a trace that gets cut, and a jumper wire is run from U6-Pin 9 to U16-Pin 11. This makes it so that when you are in Edge or Distortion Modes, Channel 1 Volume control is active. If you are in Clean 1 or Clean 2, then Channel 2's Volume control is active. Cool!!!!

Other than that, 2 diodes are lifted on one side (CR210 and CR213) so that the channel switching control signal can be intercepted before getting to the channel switches. Instead, I used a 4052 (1 in 4 out) to control the signal that selects the mode.

Really, this is a pretty easy mod to perform. The hardest part is building the circuit, which consists of:

(1) IC 4052
(4) Diodes (1N914)
(1) LED (I used yellow, but I think any color would work)
(5) 100k resistors
(1) 560 ohm resistor
(1) Jack

Here's the modified schematic for the output section of the Sustainor. I'm guessing it's OK to post it since it's past it's patent expiration date.