You can thank Mike Beigel for nearly 45 years of quacking and bubbling guitar tones. Beigel’s Mu-Tron III, introduced in 1972, was the first envelope filter—a wah-like effect where the filtering is controlled not by a foot pedal, but by the player’s dynamics. For many, the Mu-Tron III, as heard on Jerry Garcia’s guitar, Bootsy’s bass, and Stevie Wonder’s clavinet, remains the definitive envelope filter.

Fans of the original effect are likely to love Wonderlove from Seattle’s 3Leaf audio. But it’s no mere clone: Wonderlove covers all the Mu-Tron III bases while adding many expressive extras, and it all fits inside a standard BB-sized stompbox that’s much smaller than the original’s size 15 footprint. An AC adapter (not included) is required; there’s no battery option.

Quack Attack
Wonderlove’s control panel is tightly packed with six high-quality switches and seven ergonomic MXR-style knobs. Dual relay-style footswitches activate the effect and enable expression pedal control. (More on that in a bit.) Inside are plastic board-mounted jacks and a circuit board populated with modern surface-mount components.

Shaping tones with an expression pedal adds variety, expressivity, and a hell of a lot of fun.

Operation will be intuitive for Mu-Tron III vets. As on the original, you fine-tune the filter response via delicate manipulation of sensitivity and resonance controls. Tiny adjustments can trigger dramatic changes, so dialing in the perfect response for your pickups and playing style can require patience. Other familiar features are switches to select filter type, change the sweep direction, and toggle between low and high filter cutoff frequencies. (The low setting works great on bass.)

So far, everything operates as on the original, and despite the modern components, the tones are spot-on. If the features ended there, you’d have a fine modern update of a classic effect (as heard in the first audio demo clip). But oh, there’s more.

On Beyond Tron
Additional controls unlock tones you can’t get from a Mu-Tron III. A range toggle offers a choice between classic response and a cool alternate voicing, while a boost knob lets you whack the filter input for more extreme effects. A blend knob mixes direct and filtered signal. (It’s especially useful on band-pass filter settings, allowing you to access those wah-like timbres while mixing in full-frequency signal to retain bass mass.) Meanwhile, dedicated attack and release controls further shape the filter response. Their settings can determine whether the filter goes blip, shlurp, or boooooo-waaaah. There’s also an added low-pass tone control after the filter to tame shrill highs.


Fine vintage envelope filter tones. Cool modern variations. Real-time control. Effects loop. Ingenious switching. Quality build.

No dedicated filter cutoff control. No battery option.


Ease of Use:





3Leaf Audio Wonderlove

Things get even more exciting with an expression pedal (3Leaf recommends the Dunlop DVP3 because of its taper). The pedal controls the cutoff frequency in wah-like fashion. (The pot’s range and taper differ from those of common wahs, so you may need to put in some practice before replicating your usual wah moves.) Shaping tones with an expression pedal adds variety, expressivity, and a hell of a lot of fun (as heard in the second audio demo clip). Clever detail: The second footswitch toggles between controller mode and conventional operation.

Totally Buff
Another cool feature is a switchable buffer. You can flick it on for a louder, brighter signal over long cable runs, or bypass it when feeding effects that don’t play well with buffers—especially fuzzes.

And chances are you will want to connect a fuzz. Wonderlove’s remaining killer feature is a built-in effects loop, and inserting a fuzz unleashes all manner of violence. You know all those interesting shades you get when you connect a wah upstream from a fuzz? Wonderlove rockets that effect to the moon. The shifting filter peaks draw new colors from the fuzz. The fuzz’s compression draws new colors from the filter. Fans of unconventional distortion tones will flip. (For the third audio demo clip, I connected a Catalinbread Katzenkönig, a Rat/Tone Bender hybrid.)

You can even choose whether the looped pedal remains active when Wonderlove is bypassed. That means you can alternate between filter alone, filter plus looped effect, or looped effect alone, just by footswitch. You can also use the effect return jack to trigger filtering from external audio sources—drum tracks, for example.

The Verdict
Wonderlove nails the expected envelope filter tones plus many others. It’s compact, well made, and reasonably priced considering its quality hardware, design innovations, and creative potential. Guitarists who like vintage envelope filters will like Wonderlove. Players who dig those effects but wish they’d do more will adore it.

Watch the Review Demo: