The stock tube is an ECC832, which pairs half of a 12AX7 with half of a 12AU7. The socket also accepts common dual triodes such as the 12AX7, 5751, 12AT7, 12AY7 and 12AU7. Each type changes gain and response, so swapping tubes becomes part of the tone-shaping process.

A Bias knob sets the current through the tube. Counter-clockwise settings give a gated, broken-up texture, while clockwise settings clean the circuit up. A three-band EQ with a wide-ranging Mid control follows the drive stage.

Two push switches refine the setup. Fat/Tight trims the low and low-mid content reaching the tube, which helps with darker pickups or bass-heavy amps. A switchable line driver adds output level and a low-impedance stage, while bypass remains true bypass.