MXR M103 Blue Box

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$88.70 to $111.00 Price Tier: Standard

4.0 (94)

16 Reviews

Find out who is using MXR M103

9 community setups

85 wishlisted

262 saved

Page last updated Jul 07, 2026

Pricing and availability

We compare 600+ stores and found this item at 8 stores. Prices updated July 7, 2026.

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4.5 (13)

$99.99

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4.5 (12)

$99.99

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4.4 (108)

$99.99 New

$87.99 Used (Like New)

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4.0 (40)

$88.70 66 available New

$54.00 46 available Used

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4.0 (35)

$99.99

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4.0 (8)

$99.99

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4.3 (61)

$113.00 $111.00 $2.00 · All time low

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£100.50

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Average Price: $94

Standard/Professional

$60

$181+

Price Tier

In the Fuzz Effects Pedals category, MXR M103 Blue Box is priced in the Standard/Professional range. This is quality gear at a fair price point, suitable for beginners, hobbyists, and pros alike.

Budget

Standard

High-end

Price History

Based on price data from 4 merchants for "MXR M103 Blue Box". Prices shown reflect NEW condition. Tracking began Apr 2, 2026.

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Description

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Unleash the beast in your guitar performance with the MXR M103 Blue Box. This pedal isn't your average distortion box; it's a monstrosity that combines aggressive fuzz with an unpredictable two-octave-down tone generator, creating a chaotic yet captivating sonic experience. The Blue Box takes your guitar signal, fuzzes it up, then duplicates it two octaves down. You have complete control over the output and the mix between the dry signal and the effect.

The charm of this pedal lies in its simplicity. With the Output knob, you can dial in the amount of fuzz you desire and use the Blend knob to adjust how much double-octave sound you want. More conservative settings yield familiar sounds, but crank the Blend knob up to 100% and the MXR Blue Box starts spitting out 8-bit-style glitches and quirks, reminiscent of an Atari console having a tantrum.

This pedal is not just an effect; it's an adventure. It's a favourite among the musically adventurous and has been used by greats such as John 5 - Rob Zombie, Jimmy Page, and Mick Thompson - Slipknot. If you're looking to add a unique twist to your sound, the MXR M103 Blue Box is the pedal for you.

Key Features:

Aggressive fuzz tones
Unpredictable 2-octave-down tones
Output and Blend controls for complete customization
Robust metal casing for longevity
Slip resistant rubber pad for stability
Powered by a single 9V battery or optional power supply
Adds a two-octave lower signal to the original signal for a unique sound

Owner's manual

MXR M103 Blue Box User Manual

Product specs

Pedal Type	2 Octave Down Fuzz
Inputs	1 x 1/4"
Outputs	1 x 1/4"
Power Source	9V DC power supply required (sold separately)
Batteries	1 x 9V
Height	1.25"
Width	2.37"
Depth	4.37"

FAQs

What kind of sound can I expect from the MXR M103 Blue Box?: The MXR M103 Blue Box delivers a unique octave fuzz effect, combining a fuzz tone with a signal two octaves lower. This creates a deep, bass-heavy sound that is ideal for experimental and psychedelic music styles.
How does the Blend knob on the MXR Blue Box work?: The Blend knob on the MXR Blue Box allows you to mix the fuzz effect with the two-octaves-down signal, giving you control over the intensity and texture of the effect.
Can the MXR M103 Blue Box be powered by a standard 9V adapter?: Yes, the MXR M103 Blue Box can be powered using a standard 9V DC power supply, such as the Dunlop ECB003, or a 9V battery.
Is the MXR M103 Blue Box suitable for bass guitar?: While primarily designed for electric guitar, the MXR M103 Blue Box can also be used with a bass guitar to create unique, heavy octave fuzz sounds.
Does the MXR M103 Blue Box have true bypass?: Yes, the MXR M103 Blue Box features true bypass switching, ensuring your signal remains unaffected when the pedal is not in use.

Videos

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ProGuitarShopDemos

MXR Blue Box Fuzz / Octave

ProGuitarShopDemos

MXR Blue Box Octave Fuzz

jimdunlopusa

MXR M103 Blue Box Octave Fuzz | Reverb Demo Video

Reverb

MXR Blue Box - 2 Octave Down Fuzz Chaos! | Gain Appreciation

Science of Loud

MXR M-103 Blue Box Pedal Video Demo

tunnelvisionmusic

MXR M103 Blue Box Octave Fuzz Demo - Harmon Music - HIGH DEFINITION

Harmon Music

MXR M103 Blue Box (Octave Fuzz)

Dandy and The Cosmic Official

Reviews

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PROS

Unique fuzz/octave effects create distinctive sounds
Durable, "built like a brick" construction
Inspires creativity with glitchy, bitcrusher sounds for unique lead lines
Versatile for various genres including rock, metal, and experimental music
Simple operation with just two knobs (blend and volume)
Can achieve thick sub-octave fuzz and gritty unstable fall-off
Affordable for the unique tonal options it provides
Capable of generating 8-bit, video game-like tones
Can be modded for improved functionality and sound customization
Works well when combined with other effects pedals

CONS

Volume drop when pedal is engaged, requiring mods or additional pedals to correct
Not suitable for polyphonic playing; best with single notes
Limited controls with no separate fuzz or tone adjustment
Not ideal as a primary fuzz pedal due to its specific and quirky sound
The heavy distortion of the octave effect can muddy sound separation
Requires experimentation to find the sweet spot for the desired effect
The blend knob's range from bland fuzz to overpowering octave can be hard to balance
Some users find the pedal's unique effects too niche or impractical for regular use
Not conducive to all musical styles, particularly traditional rock or blues
Can be challenging to fit a 9-volt battery due to internal foam placement

Owner Insights

We analyzed real musician discussions from forums and Reddit to find what players love, question, and tweak about MXR M103 Blue Box.

Setup and maintenance

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Improved tracking can be achieved by using the neck pickup with the tone control rolled back completely.
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Comparisons

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Some users find the Blue Box's output too low compared to other fuzz pedals, preferring alternatives like the Meatbox for more pronounced octave-down effects.
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Catalinbread Perseus is suggested as a more refined alternative, offering similar sounds with potentially better build quality.
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The Blue Box is likened to the FX33 Buzz Box when combined with a ring modulator, offering an alternative to this expensive gear.
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Users compare the Blue Box to the Atreides, which shares its quirky nature but is noted to be louder.
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Use cases and applications

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Experimentation with running drums through various fuzz pedals is encouraged, with one owner noting success using a Bass Big Muff for distinctive filtered distortion tones.
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The Blue Box is praised for its ability to create "Them Crooked Vultures" and "Queens of the Stone Age" inspired tones, enhancing hard blues and lo-fi drum tracks.
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Works exceptionally well when paired with additional fuzz pedals or a wah pedal for more experimental sounds.
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It can create retro video game sounds, making it appealing for younger guitarists or those seeking nostalgic tones.
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The pedal excels at replicating the "Fool in the Rain" Jimmy Page sound and is also linked to Melvins' early work.
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Mods and upgrades

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Owners reinforce the benefits of removing a treble bleed to achieve louder output, enhancing the pedal's usability without altering key frequencies.
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Adding a switch to toggle between one or two octaves down is suggested to enhance usability and versatility.
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A recommended mod involves removing capacitor C11 to mitigate volume drop, reportedly increasing volume noticeably without altering tone significantly.
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Build quality

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The bypass on older script reissue models is noted for being less effective, subtly affecting tone at higher volumes.
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Features and functionality

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The MXR Blue Box is characterized by its unique, chaotic octave-down fuzz, often described as sounding like a "dying Nintendo."
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The Blue Box's monophonic nature allows it to play only one note at a time, enhancing its glitchy sound profile.
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