Variac

Discrete analog circuit modeling a tube amplifier's preamp and power amp stages with separate gain stages and interactive tone stack. Named after the variable AC transformer used to starve tube amps of voltage.

Preamp (gain/distortion before tone stack), Treble, Bass, Power Amp (master volume-style gain after tone stack), and Phase Inverter switch selecting between Cathodyne (more bass, looser response) and LTP/Long Tail Pair (tighter low end, more focus). Controls interact like a real amplifier.

Accepts 7.5V to 18V DC—lower voltages simulate amp sag and brownout effects, higher voltages increase headroom. The Cathodyne/LTP switch models two actual phase inverter topologies found in vintage tube amps, a deep-cut feature rare in overdrive pedals.