The Electro-Harmonix Bass Micro Synthesizer is a pure bass guitar synthesizer with all analog circuitry, made to put fat analog synth textures under a bass line and, as the maker puts it, give your bass "a whole new range of possibilities"1. It was released in 2008 and remains part of Electro-Harmonix's bass line, alongside pedals like the BassBalls and the Bass Big Muff Pi1.
What it does to a bass sound
Electro-Harmonix describes the pedal as optimized for bass guitar, built around synth-style filter and octave effects1. The design descends from the guitar-oriented Micro Synth, which reviewer Barry Rudolph described as allowing "a guitarist to make some of the same sounds as the Moog™ Synthesizer"2. On the bass version, that same analog approach is tuned for low strings.
Reviewers have placed it in a particular corner of the bass synth world. In a Guitar World review of a competing pedal, Connor Flyns characterized the Bass Micro Synthesizer this way: "this is an analogue synth pedal which offers a much more old-school experience"3. That old-school character is the point of the analog circuit: it behaves like a vintage synth voice rather than a digital modeler.
Controls
The pedal's controls shape how the synth voice responds to your playing:
- Attack Decay: Determines the time required for the voice signals to reach full volume1. RockBoard's PedalPedia entry for the vintage version notes it "creates bowed effects or ominous volume swells"4.
- Footswitch: Selects either effect mode or bypass. When the Status LED is lit, the pedal is in effect mode1.
The related guitar Micro Synth pairs an Attack Decay-style control with a Sub-Octave volume control, which "Controls the output volume of the Sub-Octave"5, and Barry Rudolph's review of the Micro Synthesizer describes Filter Sweep controls including "Resonance, Start Frequency, Stop Frequency and the Rate of Sweep," where Resonance "adjusts the resonance of the filter sweep"2. Those filter and octave voicings are the core of what the bass version carries over.
Power, bypass and connections
The Bass Micro Synthesizer runs on the included 9.6VDC-200mA power adapter and draws 55mA1. It is true bypass, so when off, your bass signal passes straight through1. Audio is mono: a single Output jack "outputs the Bass Micro Synthesizer's audio signal"1.
The pedal draws 55mA and ships with its own 9.6VDC-200mA adapter1. Players adding it to a daisy-chained board should make sure their supply can cover the draw at the correct voltage.
How it compares
Electro-Harmonix also makes the guitar-focused Micro Synth, which shares the analog synth approach but is not optimized for bass5. Players looking for polyphonic octave effects in a digital design will find a different animal in the Micro POG, which Electro-Harmonix lists as digital6. The Bass Micro Synthesizer sits in the analog, monophonic synth-voice camp, and for a broader look at the category, see Synth Pedals and Bass Pedals.
Videos
EHX
Guitarsenal
Questions
Is the Electro-Harmonix Bass Micro Synthesizer analog or digital?
It is analog. Electro-Harmonix lists the circuit as analog and describes the pedal as a pure bass guitar synthesizer with all analog circuitry. That analog design is what gives the pedal its synth-style filter and octave character, and it is the same approach Electro-Harmonix uses on the guitar-oriented Micro Synth.
Is the Bass Micro Synthesizer true bypass?
Yes. Electro-Harmonix lists true bypass among the pedal's features. When the pedal is off, the footswitch selects bypass and your bass signal passes through without the synth circuitry in the way.
Does the Bass Micro Synthesizer come with a power adapter?
Yes. Electro-Harmonix includes a 9.6VDC-200mA power adapter with the pedal. The pedal draws 55mA, so the included adapter covers it, and players should match the adapter's voltage and current rating if they power it another way.
Is the Bass Micro Synthesizer mono or stereo?
It is mono. Electro-Harmonix lists the audio as mono, with a single Output jack that carries the pedal's audio signal. No stereo outputs are part of the design.
What does the Attack Decay control do?
The Attack Decay control determines the time required for the voice signals to reach full volume. In practice, Electro-Harmonix's PedalPedia entry for the vintage version says it creates bowed effects or ominous volume swells, letting a bass note fade in rather than hit at full level.
Sources (6)
- Bass Micro Synth, Electro-Harmonix
- Electro-Harmonix Micro Synthesizer, barryrudolph.com, 2021
- MXR MB301 Bass Synth Pedal review, Guitar World, 2025-08-01
- Bass Micro Synthesizer (Vintage) by Electro-Harmonix, RockBoard PedalPedia, 2026
- Micro Synth, Electro-Harmonix
- Micro POG, Electro-Harmonix
