When to activate the buffer in GSC-3/2 ?

Input buffer in the GSC-3/2 controller enables signal power gain (without voltage change) and it has impedance identical with a tube amp (1 Mohm).
When activating the buffer the guitar is loaded only by the guitar cable and by the buffer.
Comparing to the guitar the buffer has manifold bigger ‘power’ so the element after the buffer ( e.g. cable connecting GSC with the amp or active effect) will have no influence on the guitar tone. Such influence normally occurs when the cable connecting the GSC with the amp is quite long (e.g. 6m) and when it has big parasitic capacitance (high tones will be attenuated). It would occur also when the first effect in the signal chain would have low input impedance (if you don’t use the buffer your guitar tone will change).
However some guitar effects will sound better when the buffer is turned off. It is recommended to check if the given effect sounds better with or without the buffer.