To build a simple (series) effects loop to add/remove noisy or otherwise malicious components (i.e. crapy bypass pedals) out of the signal chain when not needed.
To add the simplest an purest sounding of all buffers to a simple 3PDT based switcher.
4un. jack sockets
1un. 9V battery snap
1un. 1Mohm resistor
1un. 3k3 to 10k resistor
2un. quality caps (anywhere from .22uF- Higher values means lower frequencies pass. I hear no difference from .47uF onward...)
2un. 390ohm resistors
1un. 3PDT stomp switch
1un. SPST toogle switch
Principle of operation:
1- The signal arrives from the guitar at the input jack;
2- It then enters the FET buffer which provides a high impedance input and a unity gain output signal. Great for driving whatever comes next (be it long cables or lots of true bypass effects).
3- From there it goes into the center of the 3PDT where it gets sent either to the OUTPUT or to the SEND jack
4- If sent to the SEND ith thet travel through whichever is connected to the SEND-RETURN and it is thrown into tht output. Simple.
5- The remaining pole of the 3PDT is used to provide a visible status indication (via one of the LEDs).
6- The toggle switch is used to turn the unit on/off.
The unit can be used as a AB box if the instrument is connected to the INPUT and oune output is pulled from the OUPUT and another from the SEND
The assembly results in a super silent unit that draws very little power and does not (at least to my ears) alter the signal in an audible fashion.