While “true bypass” is all the rage in guitar effects pedals these days, there are downsides. Namely that the input impedance on many effects pedals is too low and, combined with long cabling, tone suffers — especially high notes and overtones so important for leads. By using a high-impedance buffer close to the instrument, it will be unconcerned by switching pedals on and off and the tone’s full potential can live on. (of course the guitarist must do his or her part too!).
Here’s a simple high-impedance input buffer I’m using to drive single-coil guitar signals through long effects chains. The small-signal impedance is around 1Mohm, like most tube amps. Using a “bootstrap” design for the high impedance, we can avoid Johnson noise from large resistors (e.g., if it instead used a 1Mohm resistor in the input).