Boost and Buffer

A buffer doesn't change your tone — it changes who's actually 'listening' to your guitar's pickups, protecting the signal from cable capacitance and a long pedal chain's cumulative loading. A boost is the same circuit with gain added. This chapter covers why both exist, why they're the simplest gain stage in this book, and the one common circuit — fuzz — that actively doesn't want one in front of it.

Boost and buffer are the simplest gain circuits in this book, and they’re deliberately the last chapter for that reason: everything needed to understand them — a controlled op-amp or transistor gain stage — was already covered in op-amps and transistors and diodes. What’s new here isn’t the circuit, it’s why something this simple is worth building at all — and its simplicity is exactly why breadboarding and prototyping singles it out as a good low-stakes circuit to practice the prototype-before-you-commit habit on: a handful of parts, one gain stage, and a result you can judge by ear immediately.

The mental model: a buffer changes who’s listening, not what’s said

A guitar’s passive pickups are a comparatively weak, high-impedance signal source, and what’s connected downstream of them — a cable, a pedal’s input, an amp — actually affects the tone that reaches your ears, because a long cable’s capacitance interacts with the pickup’s inductance and rolls off high frequencies the further the signal has to travel before being “picked up” by something with a low input impedance. A buffer is a circuit whose entire job is to present a high input impedance to the guitar (so it doesn’t load the pickups down) and a low output impedance to everything after it (so the rest of the chain, however long, doesn’t matter anymore). Nothing about the audio is amplified in a musically meaningful sense — a buffer’s gain is unity, exactly 1x — but the signal’s ability to survive a long cable and a pedalboard full of other pedals without losing treble is exactly what it exists to protect.

Buffer vs. boost: the same circuit, one resistor value apart

A boost is a buffer with gain added — literally the same non-inverting op-amp topology (or a comparable transistor gain stage), with the feedback resistor ratio set to something greater than 1 instead of exactly 1. Where a buffer’s job is purely preservation, a boost’s job is to push the signal louder before it hits the next pedal or the amp’s front end — useful for a volume lift going into a solo, or for driving an already-overdriven amp or fuzz harder into its own clipping.

True bypass vs. buffered bypass

A “true bypass” pedal, when switched off, disconnects itself from the signal path entirely — nothing about the pedal touches your tone when it’s off, but it also does nothing to counteract cable-length tone loss. A “buffered bypass” pedal keeps a buffer stage active in the path at all times, even when the pedal’s main effect is switched off, which is why a pedalboard with one well-placed buffered pedal near the start of a long chain of true-bypass pedals commonly sounds noticeably brighter and more solid than the same chain with no buffer anywhere in it.

Common mistake: putting a buffer in front of a fuzz

This is the one place a buffer actively makes things worse rather than better, and it directly connects back to fuzz’s input-loading quirk: a Fuzz Face-style circuit depends on seeing the guitar’s own passive pickups and volume pot directly, because that specific, non-standard input impedance is part of what makes its bias point (and its volume-knob cleanup behavior) work the way it does. A buffer sitting in front of it presents a low, stable output impedance instead of the guitar’s own — which is precisely what a buffer is designed to do everywhere else — and that changes the fuzz’s bias point and clipping character, usually described as the fuzz sounding thinner, more compressed, or “wrong” compared to plugging straight into it. The fix is ordering, not a different buffer: place any always-on buffer after a vintage-style fuzz in the signal chain, never before it, and if a pedalboard’s buffer placement is fixed, put the fuzz in a spot upstream of it or accept that the fuzz needs to run first.