ELECTROHARMONIX Q TRON ENVELOPE FILTER ΠΕΤΑΛΑΚΙ Improve your Groove. The phattest, funkiest envelope filter ever made! Switchable Boost and Filter modes allow for an unlimited supply of new auto-wah effects that drip with attitude. Increased frequency response and improved signal-to-noise ratio make the Q-Tron perfect for use with any instrument. Bootsy Collins and George Clinton already have theirs. How about you?