I'm looking at this schematic:
http://www.thatcorp.com/pedals/4320%20Battery-Powered%20Compressor-r00.1.pdf
And wondering what the 100R (R3) is doing on the output of the circuit. How would varying this affect tone or output impedance?
> what the 100R (R3) is doing on the output of the circuit.
http://www.geofex.com/circuits/what_are_all_those_parts_for.htm
If you hang a long-long cable on the output of a naked chip, it will oscillate radio waves, and not do good with audio at the same time. NO effect on "tone". Output impedance is "very low", say 101 Ohms. Just do it.
BUT these THAT circuits may not be fully checked. You for-sure want a Output Coupling Cap, because the output sits at +4.5V DC.
And the input impedance is just 6K, far too low for many points in a guitar-chain.