Electro-Harmonix · Q-Tron · Mid-1990s–2017

EHX Q-Tron

The Q-Tron is Mike Beigel's second go at the envelope filter. Beigel co-founded Musitronics in 1972 and invented the Mu-Tron III, which Musitronics sold as the world's first envelope-controlled filter and Stevie Wonder put on his Clavinet for Higher Ground. Musitronics was gone by 1979. In 1995 Mike Matthews hired Beigel to design a new envelope filter for EHX on the same analog circuitry as the Mu-Tron III. The Q-Tron kept the old controls and added a Boost switch that brings in an internal preamp, which gets it very close to the original Mu-Tron. The harder you pick, the further the filter opens, like a wah that plays itself. You get low-pass, band-pass and high-pass modes, a Peak control for resonance, a Hi/Lo range switch and a switch that sweeps the filter up or down. EHX says Bootsy Collins and George Clinton have theirs. The Q-Tron+ added an effects loop and a Response switch, and EHX lists the plain Q-Tron as discontinued in 2017. If you want the Mu-Tron sound in a pedal that's easier to find, the Q-Tron is the shortcut.