The LPB-1 is a good value for the money, but there are two ferrite beads and two 100pF capacitors left in the signal path even when the circuit is bypassed. The additional capacitance could create an upper frequency loss when driven by a high impedance source like guitar pickups.
This mod removes those components, which were not on the 1960s original, and converts the pedal to the more typically understood definition of true bypass.
Remove C4 and C5 – not needed. Replace FB1 and FB2 with jumper wires. Done.
It will then be 100% true bypass with nothing but wire between the input and output jacks when bypassed.
These instructions are for the “Rev. B” circuit board.