Preamplifier

The circuit began as a traced copy of a 1970s Boss product that was not designed only for guitar. Later changes let it push a tube amp near breakup, or stay on as a smaller lift. Input gain sets how hard the signal hits the preamp. Output level sets that result against the bypassed sound, or drives the amp harder. The Low cut switch rolls off below a point between 40 Hz and 90 Hz. That corner moves with the input-gain setting. The High cut switch rolls off above 3 kHz at 6 dB per octave.

A VU meter shows how hard the pedal is driven. Its backlight is also the bypass indicator. The maker has also used the circuit on bass and keys, and as a hardware insert for drums and vocals.