Electro-Harmonix Q-Tron Plus Envelope Filter with Effects LoopMaker: Electro Harmonix Model: Q Tron Plus Condition: New Description: Same design as the original EHX Q Tron but with extremely useful Effects Loop and an Attack Response Switch. The Effects Loop gives the musician the ability to place an additional effect, or chain of effects between the EHX Q Tron Pluss preamp and filter section without changing the envelope drive. This is particularly important with most distortion devices, as most all do not have