Compare 12AX7, 12AT7, 12AU7, 12BH7 and 12BZ7 with interactive waveforms, harmonics, load lines and Miller loading. Original manufacturer data and clear modeling limits explain why a tube swap can change the sound.

Closing the series with the plug-in fuzz: the Boss Tone’s capacitive-coupled dual-NPN cascade, saturating twice before a symmetric diode clip.

Boost, clip, buffer: the Sam Ash Astrotone topology does its clipping with a symmetric diode pair at plus and minus 0.6 V.

Two saturating stages blended in antiphase: the Fuzzrite’s parallel phase-blend gets its buzz from subtractive mixing.

Full-wave rectification by differential pair: Roger Mayer’s Octavia doubles the frequency and overdrives the stages on the way through.

A modified Darlington front end driving two clipping stages in series: the Sola Sound Tone Bender MkII topology.

Two transistors, shunt-series feedback, and a strongly asymmetric gain-dependent clip: the Dallas-Arbiter Fuzz Face topology.

Kicking off a seven-part bench series: how to read the schematics and clipping diagrams, plus the circuit that started it all, the FZ-1’s three-transistor saturation cascade.