Electro-Harmonix Bass Mono Synth Review

Big, warm, analog synth sounds for your low go.

Recorded direct into Avid Mbox into Logic X using Sandberg T5 with both pickups engaged.
Clip 1: Synth type set to Twin. Dry control at noon, synth control at 2 o’clock, sensitivity at noon, and ctrl knob at 11 o’clock. 80 Hz boosted.
Clip 2: Synth type set to Oblivion. Dry control at noon, synth control at 2 o’clock, sensitivity at noon, and ctrl knob at 11 o’clock. 50 Hz cut and 2 kHz boosted.


Several usable sounds. Basic programmability. Compatibility with an expression pedal.

Slightly picky with tracking.


Electro-Harmonix Bass Mono Synth


Ease of Use:



Reproducing classic analog synth sounds on an electric bass is something I dreamed of as a kid, during my first years as a bassist. But the pedals available at the time never quite hit the spot. I felt they had tracking issues, added lag to the attack, or simply muddied up the tone—the things actual keyboards don’t do. Even though I’ve had some synth pedals that raised my eyebrows and made their way to my pedalboards for various amounts of time, I haven’t found one that stuck. It’s usually only one or two of the preset modes that are even remotely useable, so I usually end up using my “faux” synth-bass chain consisting of a fretless bass, octave pedal, and an envelope filter. So, yes, it was with some skepticism that I checked out the new Bass Mono Synth from EHX, but the majority of my concerns were quickly erased.

Lay It Out
The pedal has an attractive exterior with an original color scheme. The large, cream-white controls are an instant win and their positioning just plain makes sense, with the dry control far to the left. The neighboring “synth” control regulates the level of the synth-y goodness. The sensitivity control operates in conjunction with the LED light to assist a player in getting to a good input level. Many of the 11 synth presets available require the input signal strength to be just right when hitting the effects processor for the pedal to do its best work. The control dial affects a different parameter for each synth type, which is clearly explained in the well-written manual. A custom, programmable user patch is also available foreach of the 11 synth variations available by changing the “type” control.

The moment I plugged my Sandberg TM5 into the pedal and started scrolling through presets and turning knobs, a smile spread across my face.

Zero to Grin in Two Seconds
The moment I plugged my Sandberg TM5 into the pedal and started scrolling through presets and turning knobs, a smile spread across my face. Right away this pedal made me want to play classic, big, simple lines. The “oblivion” setting treated me to a large, all-frequency-filling, vintage-yet-modern sound that can be very useful for EDM-leaning material. The “growl” and “acid” presets needed very minimal tweaking to achieve a bubbly, creamy, and chocolate-y sound that made me want to lay into some Gap Band tunes. Behind the “twin” setting hides a punchy, heavily growling tone that would cut through a wall of competing, thick synth patches playing chords in a band setting. The pedal tracks fairly well, but it does demand you play cleanly for its best performance, since it truly is monophonic. In order to help the pedal along, it’s also crucial to place it at the very beginning of a signal chain.

The Verdict
A pedal will never feel like playing a keyboard, but when carefully tweaked, the sounds oozing out of the Bass Mono Synth will get you through a gig when you need to get close to the real thing. If you are new to synth effects, the Bass Mono Synth is a comprehensive but easy-to-navigate starting point, with more than enough gooey Hershey’s syrup to sweeten up your palette.

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