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MXR M68 Uni-Vibe Review

MXR M68 Uni-Vibe Review

An FET-driven vibrato and chorus that captures the sound and spirit of a classic.

There’s no questioning the cool designs and visceral sonic appeal of ’60s guitar effects. The practical shortcomings, however, can make them hard to live and work with. Take the original Univox Uni-Vibe. It’s a legend—the swirl in epic psychedelic sundaes from Jimi’s “Machine Gun” to Pink Floyd’s “Breathe.” It’s also a complete pain in the rump—a cumbersome assemblage of expression pedal, wires, switches, and an optical circuit packed into a clunky box that might as well be marked “auto-destruct unit.” Hell, you could argue that the mammoth Leslie speakers the Uni-Vibe was built to emulate (yes, the exalted Uni-Vibe was once itself just a cheesy, ersatz rotary speaker) would be the simpler way to put a little wobble in your jams. Weigh those facts, and it’s easy to understand the appeal of a Phase 90 and a 9V battery.

So with romantic notions about the original Uni-Vibe put to rest, let’s dispel another suspicion you might harbor right off the bat: MXR’s new, compact M68 Uni-Vibe is not an optical circuit-driven Uni-Vibe miraculously shrunken and stuffed in a compact enclosure. What it is, is an excellent FET-driven, analog chorus/vibrato that swirls with depth and character and delivers a pretty authentic approximation of the original Uni-Vibe tones—especially in the chorus setting—for a relatively tiny chunk of change.

Sturdy Little Modulation Machine
Like the original Uni-Vibe, the M68’s circuit is housed in a matte-grey enclosure that appears lifted from a ham radio operator’s rig. Unlike the original, it doesn’t have a cool, engraved plastic control panel. MXR opted instead for a screen-printed facsimile. But that cost-saving detail aside, there’s enough of the original Uni-Vibe’s industrial-cool styling at work here to make the pedal’s intent clear.

Though the M68 Uni-Vibe lacks an expression pedal (a design decision that vintage buffs will decry) the controls are similar in function to Dunlop’s expression-pedal-based Rotovibe. On the M68, the speed knob takes the place of the Roto-Vibe’s expression pedal, the depth knob is mounted on top rather than the side, and the small “vibe” button on the M68 takes the place of the chorus button that’s side-mounted on the Roto-Vibe.

One of the biggest advantages the M68 Uni-Vibe has over the Roto-Vibe is its level control. As we’ll find out, this expands the tone and expressive range of the M68 and lends an extra measure of authentic Uni-Vibe depth and color.

If your tastes lead you to the more psychoactive realms of the chorus effect, the MXR is capable of some very twisted and unorthodox tones.

Chorus for the Chorus Averse
One of the most satisfying ways to get to know the M68 Uni-Vibe is to start with the default chorus setting and set the speed and depth slow. Right away you’ll hear how the M68 differs from the icy, artificial chorus tones that have scarred digital-averse listeners since the ’80s. The M68’s chorus textures are organic and rich (if not exactly super-lush) and each modulation cycle has a very pleasing and natural taper that’s free of jagged, square-wave overtones or harsh clipping.

A great place to commence exploring the chorus sound is to set the speed at 10 o’clock and depth anywhere between 10 and 2 o’clock, and then strum Em. You’ll hear a dang-near dead-on approximation of Gilmour’s languid, Uni-Vibe derived tone on “Breathe.”

From these familiar grounds, you can investigate the throbby fast settings (which remain impressively organic and smooth sounding at the fastest speeds and most intense depth settings) or the lazy rotations of the slowest modes. Each extreme and the zones in between can make ordinary chords and single-note lines sound lively, and while there might be fatter sounding analog chorus pedals, the M68 replicates some electro-mechanical nuances of a real rotary speaker—natural-sounding Doppler rise and fall, and smooth overtones in particular—with satisfying ease.

The chorus mode is made more flexible and expressive by the level knob. As a boost, it’s pretty mellow, but it adds low- and low-mid emphasis that enhances the rubbery qualities of the chorus. It also has the effect of giving the depth control more range and flexibility, and using the two together helps you really tailor the elasticity of the sound to suit specific guitars, pickups, and amps. This aspect of the control setup pays major dividends if you want to use the pedal with a fuzz, and you can really excite frequencies from a fuzz or overdrive that might otherwise be lost in the tone vortex. The additional low-mid push also fattens up the swirl, and aggressive use of the two controls together is especially handy for thickening the output of Stratocaster-type pickups. Aspiring Jimis and Ernie Isleys will undoubtedly love what the MXR can do in this setting.


Organic modulation tones. Level control adds tone shaping power and a boost.

Vibe effect is super subtle at slow speeds


Ease of Use:




MXR M68 Uni-Vibe

If your tastes lead you to the more psychoactive realms of the chorus effect, the MXR is capable of some very twisted and unorthodox tones. And maxing each control produces heavy, near-synthy, almost repeat percussion-like sci-fi pulses.

Mad and Mellow Vibe
Interestingly, the M68’s vibe settings often have a more retiring personality, especially at slow speeds. Where the chorus is fairly pronounced at very slow settings, the vibe effect is barely perceptible until somewhere between 9 and 10 on the speed knob, where it starts to take on a woozy, elastic, narcotic quality that’s a perfect match for sleepy chord arpeggios.

As with the chorus, the pulses have a naturally contoured taper and harmonic depth that are a great stand in for a rotary speaker in motion. And though the highest speed setting produces a complex, queasy pulse that seems to move on multiple axes, it still sounds very organic. These faster speeds sound even more detailed at reduced depth settings. You’ll also hear more shake in the high frequencies when you roll back the depth control. And the resulting tones can do a fine impersonation of the high, humming whirr of a Fender Vibratone if you set the speed right.

The Verdict
The fact that the M68 isn’t the deepest or most mind-warping chorus tone will actually be a benefit to a lot of players. And its civilized, play-nice nature makes it the ideal chorus for any player who likes the effect as a secondary texture rather than the underpinnings of a riff. That said, the M68 can sound fat enough in chorus mode to please all but the most obsessive Jimi and Gilmour fiends—especially with a fuzz. And the maniacal pulse of the fastest vibe and chorus settings can re-cast the simplest riff or lead into a psychedelic voyage. For just less than 130 bones, it puts a lot of very tasteful, natural, and even demented modulation effects at your fingertips—all in a package that’s compact, intuitive, and doesn’t require it’s own full-time tech.