I built this in the form of a stomp box pedal.and have a few observations and suggestions following a consultation with an electronics bench technician. The DPDT switch is not necessary, as a true bypass can be accomplished with a SPDT (see image below with original circuit and my revised circuit). A had him ad a separate circuit to the other side of the DPDT so that I could have an indicator LED when the effect is engaged. I am not using a battery as shown in the schematic - the battery has been replaced with a jack so that it can be powered from my pedal board power. The final circuit actually sounds a little better to me (more effect available-the one that treats the switch as a DPST). Also, the use of an Audio Taper pot is not recommended in this circuit. A Linear Taper will give a more even balance of the effect. To add this directly to your guitar (or bass in my case) a push/pull pot can be used to engage the effect and adjust the amount of effect with one control.