If you know how typical envelope filters work... well, forget them, because MXR didn’t copy them. Instead, they’ve re-defined what an auto-wah can do to funkify your sound.
The MXR Auto Q from Jim Dunlop triggers at any playing level, not just on your loudest notes. The Auto Q’s effects are amplitude independent, so you get exactly the same effects at high volume or low. Come out front with your solo then drop back for a rhythm fill – your tone mods stay constant throughout.
It’s all under your control too. The RANGE knob selects how low the automatic wah will reach. The Q control, already famous on the Crybaby Wah pedal series, controls the effect’s intensity by providing a sharp frequency peak or a broader, more subtle peak. VOLUME goes to 11, natch, or anyplace below. The BAND switch selects the frequency ceiling where the effect will dominate, LO, MID or HI.
MXR has also added a whole new flavour to the Auto Q with the RATE control. RATE dials in variable shimmer that operates independently of the automatic wah section. And the BLEND rotary selects which effect has more prominence – automatic wah (turn left) or variable shimmer (turn right). Straight up and you’ve got equal doses of both!
Finally, there’s DECAY – in automatic wah, it simply controls effect dropoff. But when BLEND is set for some shimmer, DECAY controls the transition from one effect to the other. Start your note with automatic wah, and finish it off with a shimmering flourish. You can’t get these noises anywhere else!

M120 MXR AUTO Q – £1929