MXR Mini Iso-Brick Power Supply Guitar Effects Pedal - Compact

In this review of the MXR Mini Iso-Brick Power Supply, the bottom line is simple: it is a compact, fully isolated power box built for players who need quiet, reliable power on small pedalboards. The reviewer found it ideal for guitarists who run a handful of pedals and want to eliminate ground-loop hum without sacrificing board real estate. Its claim to fame is the combination of five fully isolated outputs and a small footprint, making it a practical choice for travel rigs and tight setups while still offering a high-current option for power-hungry pedals.

Key Features

• Fully isolated outputs: Each of the five outputs is isolated to reduce ground-loop noise and preserve the integrity of the guitar signal during performances.
• Four 9V outputs at 300mA: The four dedicated 9 volt outputs provide ample current for most compact analog and digital pedals used in small boards.
• Toggleable high-current output: The fifth output switches between 9V and 18V at 800mA, giving the flexibility to run higher-voltage or higher-current pedals without a separate supply.
• Space-saving footprint: The Mini Iso-Brick occupies less board area than a candy-bar style supply, making it a good fit for travel and minimalist rigs.
• Splitter cable included: The supplied splitter cable lets you power two pedals that share the same voltage from a single output when needed.

Who It's For

The MXR Mini Iso-Brick is best for gigging guitarists and home players who maintain a small to medium pedalboard and prioritize noise-free power. If you run a curated set of four or five pedals and need an isolated solution that fits into a compact rig, this unit covers most typical stompbox combinations.

Players who should look elsewhere include those with very large boards full of multi-ampers and rack units, or users who require many more outputs or specialized connectors beyond the five available. Also, musicians very sensitive to connection stability should verify fit with their pedal DC jacks since some users have reported occasional loose connections.

Pros & Cons

Pros

• Quiet, isolated outputs that effectively reduce ground-loop hum and preserve tone.
• Compact size saves pedalboard space without sacrificing useful output count.
• Versatile fifth output that switches between 9V and 18V at a high 800mA current for demanding pedals.
• Included splitter cable adds flexibility for powering two like-voltage pedals from one output.

Cons

• Some customers report occasional loose connections, so check plug fit with your pedals.
• Only five outputs may be limiting for larger boards that need many isolated feeds.

Specifications

Brand	MXR
Model	M239
Outputs	5 fully isolated outputs
9V outputs	Four outputs at 9V, 300mA each
Toggleable output	One output selectable 9V or 18V at 800mA
Included cable	Splitter cable to share one output between two like-voltage pedals

Our Verdict

The MXR Mini Iso-Brick is a smart, value-oriented choice for players who need isolated, quiet power in a compact package. It pairs well with small touring boards and home rigs, offering flexibility with a high-current toggleable output and a useful splitter. For its size and functionality it represents good value, though users with very large pedal arrays should consider a supply with more outputs.

Frequently Asked Questions

Can the Mini Iso-Brick power vintage pedals that need 9V?
Yes, the unit provides four dedicated 9V outputs at 300mA each that are suitable for most vintage and modern 9V stompboxes.

What is the purpose of the 9/18V output?
The fifth output can be toggled to 18V at 800mA for pedals that require higher voltage or more current, or set to 9V when a higher voltage is not needed.

Does it eliminate hum from pedal chains?
The fully isolated outputs are designed to remove ground-loop hum and significantly reduce noise compared with non-isolated supplies.