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Ernie Ball Expression Tremolo Review

Treadle control of tremolo and reverb unleashes an atmosphere machine.

  Les Paul, both pickups.
0:00 – Pedal off
0:05 – Sine wave tremolo, speeding up and slowing down
0:23 – Reverb added
0:38 – Harmonic vibrato, speed and reverb intensity increasing and decreasing


Good sounding tremolo and reverb, made exponentially more versatile with five waveform settings and an assignable rocker.

Control knobs can be tricky to access from playing position.


Ernie Ball Expression Tremolo


Ease of Use:



Ernie Ball is becoming a sort of aspiring king of treadle-based effects. With the Ambient Delay and Expression Overdrive under their belt, they’ve taken a logical leap forward with the Expression Tremolo. Calling the Expression Tremolo just a tremolo undersells its capabilities. Because in addition, the Expression Tremolo includes reverb—all in a rugged unit that’s about two-thirds the size of a traditional wah-wah and built to fit on crowded pedalboards. Foot-activated control over two tremolo parameters and reverb on top? Yes please! Let’s probe what this texturalist’s dream machine can do.

Depth Perception
Tremolo is arguably the oldest electric guitar effect—DeArmond introduced its Tremolo Control unit in 1941—but it’s still one of the most haunting sounds around. Amp makers from the late ’50s onward perceived that tremolo and reverb would go well together, and the Expression Tremolo applies that thinking, resulting in what could be the perfect all-in-one vintage effects machine for one-pedal players. Of course, it’s also a great addition to any well-equipped board for those looking to add atmospheric possibilities.

The works are housed in a rugged aluminum enclosure finished in gloss-purple enamel, with a grippy rubber treadle pad for slip-free rocking. The crown of the pedal is home to the input, output, and 9V DC adaptor jack, but it’s also home to the control panel, which features knobs for tremolo depth and rate, a 5-position tremolo waveform selector, and reverb intensity.

Controlling the rate with the treadle also enables particularly delectable Leslie-like effects when the wave is engaged in the harmonic setting.

Waveforms include ramp-up sawtooth, ramp-down sawtooth, sine, square, and harmonic (a brownface Fender-inspired quasi-vibrato). When you push in the potentiometer/push buttons for tremolo depth and/or rate, you assign them to rocker-control mode, which is indicated by the illumination of the LED beside each knob.

Inside, the two effects circuits are laid out across two printed circuit boards. An impressively designed and roadworthy mechanism translates rocker action to the traditional rotary potentiometer driving the rate and depth. There’s no internal 9V battery connection, so you’ll need an external adaptor (100 mA draw minimum) to power the unit (not included). Right-angle power plugs are a tight fit between the pedal’s input and output, and mid-set knob adjustments obviously incur some uncomfortable forward bending to reach the pedal’s front face, but it’s all sensibly configured for the most part.

Rocker My World
The Expression Tremolo proved tremendously versatile, offering solid-sounding effects at every turn. Rocker pedal control is a natural fit for tremolo, and while I enjoyed the ability to simultaneously dial up the mood with both depth and rate assigned to the rocker, it usually made more sense to assign just the rate to the rocker and explore acceleration and deceleration effects with the tremolo that are nigh-on impossible to achieve with treadle-less tremolo pedals. Controlling the rate with the treadle also enables particularly delectable Leslie-like effects when the wave is engaged in the harmonic setting—convincingly imitating the characteristic speeding-up-and-slowing-down thing that genuine rotary speaker horns do so evocatively.

Between the other waveform settings, it’s easy to replicate the general feel of several different classic tremolos, from the sawtooth opto-trem in blackface Fenders, to the square chop of more extreme Valco-made types, to the smooth, round bias-modulated tremolos in many vintage amps. And let’s not forget the reverb: a digital spring-inspired circuit that delivers everything from subtle, roomy washes to a deep, surfy splash. It even dished up that metallic, spring-like “sproing” when hit with a muted staccato pick attack.

The Verdict
Whether you’re into surf, moody Americana, extreme experimentalism, or anything requiring the subtle-to-extreme and classic possibilities of tremolo and reverb, the Expression Tremolo is worth a try. It’s practically an entire film score waiting to happen, and loaded thoughtfully into this compact, purple modulation machine.

Watch the Review Demo: