BASS PARALOOPER

BASS
ParaLoopBigMuff.mp3
ParaLoopFuzzFactory.mp3
ParaLoopMXRflanger.mp3
ParaLoopPhase90.mp3
ParaLoopRockyRoad.mp3

The ParaLooper is something every effects-using Bass player should have, because it will 'Bassify' any bottom sucking, high-passing guitar pedal out there. And, it's pretty simple to build, too. Instead of just an effect loop pedal, this is actually a little mixer that blends your straight signal with whatever effect (or chain of effects) you plug into the send & return jacks. There are controls for wet/dry balance and overal output level (boost & cut).

Experimenting with parallel effects chains a snap, in mono or stereo. For example, you can plug whatever effect(s) you have connected to the send into a second amplifier or mixer/recorder channel. It can also be used just like a two-channel mixer itself by plugging a second source into the return jack. There is also a low-pass filter (capacitor to ground) on the clean signal that can be switched in for even more low end.

The basis for the ParaLooper is the Bass-Thru, from a Japanese web site that happens to have some other interesting schematics, too.
Here's a PCB layout that I did:
BassParaLoop layout
BassParaLoop PCB

updated 9/20/2005
I decided to redo the PCB layout for this, to make it clearer and easier to follow. I also redrew the schematic, showing some minor component changes I made... mostly just increased the values of some of the capacitors and did away with the low-pass filter for the clean signal (I never really used it, myself). But, if you want, the value of C5 can be chosen to give more low end to the clean signal. The pads on the layout will accommodate a range of different size caps in that position. I think the stock value (0.047uF) seems to give a pretty natural sounding cutoff. But, larger values will cut more of the highs and pass more low end... adjust to taste if necessary.
Paralooper PCB Layout
Paralooper Toner Transfer
Paralooper Schematic

It's small/simple enough to build on perf-board. But, if you want to use the toner transfer image to etch a PCB, try sizing the entire image to 2.8 inches x 0.9 inches. Then double-check the pin spacing to make sure the ICs will fit before you etch... adjust the dimensions if necessary.

Off-board wiring stuff like true bypass switching and status LED are not shown in the above images. But, you can find a great write-up over at TONEPAD that does an excellent job describing the most popular ways of doing all those things... Off-board Wiring.