The Seymour Duncan Twin Tube Classic pedal emulates a high-quality tube preamp with a 100% vacuum tube signal path and true bypass circuitry. Featuring two 6021 dual-triode tubes, the Twin Tube Classic provides tone control knobs for Bass and Treble as well as Rhythm and Lead channels. Each channel has its own Volume and Gain knobs, and the Twin Tube Classic also features On/Bypass and Channel Select footswitches.