MXR Bass Octave Deluxe

The MXR Bass Octave Deluxe is an analog octave pedal for bass, made by MXR (Dunlop Manufacturing). It generates a note one octave below what you play, using two independent sub-octave voices called Growl and Girth, and blends them with your clean signal through a Dry control. MXR describes it as "a dual-voice octave pedal that offers analog tone, true bypass, and a variety of tonal options"¹.

The two voices are what set it apart from a single-voice octave box. MusicRadar's review put it plainly: "this offers two independent voices for maximum variation, blending and delivery" in "a small-sized pedal that can have a huge impact on your sound"². MXR's 18 volt Constant Headroom Technology runs the analog circuit at higher internal voltage for what the maker calls high headroom and superior tracking¹.

What it does and how it is controlled

The pedal sits in your signal chain like any other stompbox: bass in, amp out, footswitch to toggle the effect on and off, with a blue LED showing when it is on³. The three main knobs each control one voice or blend:

The Dry knob is the blend. MXR says to "use the Dry knob to mix in your direct signal"¹, so you can keep your clean low end under the octave voices rather than replacing it. MusicRadar characterized the Growl and Girth knobs as the two voices themselves, "while dry is the direct blending of the two"².

The Mid+ switch adds a midrange boost at either 400 Hz or 850 Hz, chosen by an internal slider (up for 850 Hz, down for 400 Hz)³. That boost addresses a known issue with octave effects on bass: the sub-octave content can leave you sitting under the mix. Premier Guitar's reviewer found it did exactly that job:

Analog circuit, 18-volt headroom

The Bass Octave Deluxe is an all-analog design. The M288 manual describes its sound as "organic analog tone" from "two independent sub-octave voices"³, and Guitar World's octave pedal guide calls it "an all-analog circuit, excelling at fat, chunky retro sounds"⁵. Analog octave circuits track the pitch of your input signal and generate the sub-octave from it, which is why playing cleanly and decisively, especially on the lower strings, matters for tracking.

MXR's 18 volt Constant Headroom Technology is the maker's answer to the headroom limits of a 9-volt analog circuit, providing what MXR calls "high headroom and superior tracking"¹. The manual lists a noise floor of 85 dB³.

Power and bypass

Power comes from one 9-volt battery, installed by removing the bottom plate, or from a 9-volt AC adapter such as the Dunlop ECB003 or ECB003EU, or a DC Brick power supply³. The power requirement is 9 volts DC³.

Bypass is True Hardwire, which MXR's product page describes as true bypass¹³. When the pedal is off, your signal passes through without the analog octave circuit in the path.

Where it sits in MXR's bass line

MXR makes several octave and sub-octave products for bass, and the Bass Octave Deluxe is the dual-voice analog option. The MXR Vintage Bass Octave is a single-voice analog take, which MXR describes as upgrading "the warm analog sub-bass vibes of a classic circuit with superior tracking"⁷. The MXR Sub Octave Bass Fuzz combines a sub octave with fuzz and a separate Dry volume control for clean low end retention. Guitar World's guide to octave pedals for bass lists the M288 alongside these alternatives, noting its controls of "Dry level, Growl, Girth, Mid + button"⁵.

What reviewers said

MusicRadar reviewed the pedal (as the M-228 Bass Octave Deluxe) and called it "one of the best bass effects available," praising the two independent voices for maximum variation and blending². Premier Guitar's 2026 review highlighted the Mid+ boost as a practical fix for the frequencies an octave effect can bury⁶. Guitar World's buying guide points players to its all-analog circuit for "fat, chunky retro sounds"⁵.

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