01 A buffer is a 1:1 amplifier that changes the impedance of your signal. It’s there to counteract what happens with the interaction of various physical factors: inductance in your pickups, plus capacitance and resistance in cables, pedals, switches etc. The common terminology is that they ‘drive’ the signal, minimising signal loss. Now, all pedals are buffered when they’re on. However it’s when they’re off that the principle issues arise (leaving aside fuzz which we’ll come to in a bit). True bypass is when there is no buffer in the pedal’s off state. Buffered bypass is when a buffer is in operation even when the pedal is off. It’s not necessarily a bad thing at all – the Klon Centaur, for example, is a buffered bypass pedal.
02 Some trial and error is needed to determine if you need a buffer. Plug everything in, leave all the pedals off and just play for a bit. Now, change nothing except for unplugging the cable from the ’board to the amp and plug your guitar straight in instead. If there’s a difference then you’re experiencing some signal loss. This varies with cables, guitars etc, but is most noticeable with vintage-style pickups that tend to suffer when trying to ‘drive’ a lot of capacitance. A buffer could help, but so could cleaning up your signal path with a loop switcher, and/or improving your power solution.
Now repeat that process using one pedal at a time, and then using combinations of two pedals. It’s laborious, but it should help you understand if and where the tone is being changed. The most obvious difference will be in the nature of the high-end; a strongly buffered signal will have noticeable fidelity, edge and presence that’s neither a good nor bad thing. That said, a buffer can be a key part in somebody’s tone, such as Angus Young’s.
The general advice is: 1) If you want to add a buffer, it’s usually best placed after your drive pedals. 2) Vintage-style fuzzes (Germanium fuzzes especially) tend not to like buffers in front of them. 3) Buffers after overdrive and fuzz can have an effect too, so be aware of that. 4) Once you understand what the buffer is doing to the sound, you can use it to your advantage: there is no good, bad, right or wrong!