Vintage Electro Harmonix Doctor Q Envelope Filter / Follower Effects Pedal

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  • Regular price £110.00
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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 Filter / Follower pedal 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 but, 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 operated using only two external controls, it can produce a range of great vintage filter sounds at the click of a footswitch.

This unit can run off a single 9V battery or a vintage EHX style 9V mini jack power supply so you will need an easily available adapter cable for modern Boss style power supplies (neither power supply or adaptor included).

The pedal is in incredible used condition for a vintage pedal (dated at approximately early 80s). It has just a few cosmetic signs of wear/use but really is in fantastic condition.


This item is available from our store in Exeter or by post (at an additional cost of £10 due to weight, cost of packing materials and levels of required insurance).

If postage is selected, it will be packed very carefully and sent via Royal Mail 2nd Class Signed For within 3 working days of purchase. 

If you have any questions, please contact us before purchasing either by email or phone.