1976 Electro-Harmonix Doctor Q Envelope Follower

Model Description:

Venturing beyond mainstream stomp boxes, some effects use clever analogue filters to alter the signal. This niche group of pedals includes everything from basic wahs, through pitch shifters and envelope filters to ‘synths’ and ring modulators. The American Electro-Harmonix Doctor Q Envelope Follower sits in this bracket, along with its bigger brother the EHX Zipper, both possibly inspired by the legendary Musitronics Mu‑Tron. They are often referred to as auto-wahs but they are much more than that. The filter kicks in when the input signal reaches a certain threshold and then sweeps until it tails off. Envelope followers are not for everyone. Used sparingly and skilfully, they can provide a fascinating sonic excursion, especially when combined with other effects such as echo and/or fuzz – pure ‘70s vibes. Even though the Doctor Q’s abilities are restricted by just 2 external controls, it can produce some great vintage filter sounds at the click of a footswitch.

Pedal Description:

This cool 1976 Electro-Harmonix Doctor Q is pure vintage class. It has a few scratches in the finish but then again it is decades old. It is an early model with slotted screws on the top and no battery compartment cover on the base. Two stick-on feet and one of the access screws are missing. In use, it requires a bit more effort to get the most out of it but what sounds they are, in my view so much better than the equivalent Boss T-Wah. When I got this pedal, it didn’t sound quite right. The answer lay with the internal trim pot which, after a bit of experimentation, resulted in something more familiar. Phew! Worth knowing these things! As far as I can tell, the ‘bass’ switch is essentially a bandpass/lowpass filter control, acting as a simple tone switch. The Doctor Q can be great fun and may be better suited to straightforward funky auto-wah-type effects, as the amount of fine control is fairly limited. The Doctor Q is great when feeling creative or seeking inspiration without the distraction of ‘knob fiddling’ (a guitarist’s technical term). Original vintage Doctor Qs can still be found at affordable prices, so why not grab one while you still can.


  • Made in New York City, U.S.A. in 1976
  • The ‘Range’ knob controls the frequency range in which the filter sweeps
  • The ‘Bass’ switch controls whether more or less low frequencies pass the filter
  • Standard footswitch turns the effect on and off
  • ¼” input and output mono jack sockets
  • No LED status indicator
  • DC power supply input or 9V battery
  • No battery compartment in the base of the unit
  • Slotted screws on the top of the pedal
  • No box or instructions

Detail Gallery:

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