<a href="http://www.casperelectronics.com/images/finishedpieces/BOSSds-1/S3600038.JPG"><img src="http://www.casperelectronics.com/images/finishedpieces/BOSSds-1/_S3600038.JPG" width="400" height="300" alt="" title=""  /></a><br>I experimented with a BOSS DS-1 pedal yesterday and found some really fantastic mods.
My friend brought the pedal over and showed me some mods he had found that were cool sounding feedback loops. Basically this is where the audio signal from somewhere along the signal path is fed back into an amplifier stage somewhere EARLIER in the path. This creates a feedback tone and can result in some really nice sounding, rich tones when an incoming signal fights with the feedback tone. The problem is that when there is NO incoming audio signal, there is just steady, squealing feedback.   <br>I wanted to find a way to make the effect happen only when there was sound feeding into the pedal, so that when you aren't playing into it, there's no sound output. <br> I had a suspicion that a transistor used as a gate was the answer. I experimented with some transistors configured different ways and found the 2N3904 NPN to be the most useful. I encourage people to experiment with different types though.The best effect we found is drawn below. If you have this pedal, you really have to try this! <br><a href="http://www.casperelectronics.com/images/finishedpieces/BOSSds-1/BOSSSSDS-1.jpg"><img src="http://www.casperelectronics.com/images/finishedpieces/BOSSds-1/_BOSSSSDS-1.jpg" width="300" height="400" alt="" title=""  /></a><br>It's a really great sounding effect. Sort of ringmod meets harmonic exciter of some sort. The "distortion" knob controls the effect.   
I soldered the transistor to the component side of the board so that I could still close the back cover. The back cover presses right against the solder side of the board so there's no room to add components. 