REVIEW EURORACK PATCH-CABLE ADAPTOR: 1/8th to 1/4", unlocks effects pedals

BARGAIN STUDIO HACKS

Eurorack uses 1/8" jacks and plugs, guitar effect pedals use 1/4" jacks and plugs, what's a musician to do?

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I've been looking high and low for the right way to integrate analog and digital effect pedals from my guitar rig into my Eurorack system. Let's face it, effects processors that are made and marketed specifically for Eurorack are expensive, due to the niche market Eurorack synths survive in. If you are a synth artist and also a guitar player, why not dip into that reservoir of pedals you already own to add a little shine and polish to your modular system.

For the last six months I've been experimenting with these adaptors I found. I located them by searching Amazon for "unbalanced 1/8" inch to 1/4" adaptors" (buy them wherever you like to shop). Along the way I bought several styles but the ones featured in this article are my favorite -- they're super compact, low priced and universally work with standard Eurorack patch cables.  

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Each unbalanced adaptor has an 1/8" female hole in the end of the handle, the male plug end is 1/4". 

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Using these adaptors lets you standardize on 1/8"- equipped patch cords for all your Eurorack inputs and outputs. When you want to go out of Eurorack-world, perhaps to a stomp box or even a full size rack mount processor, all you gotta do is pop one of these adaptors on the end of a Eurorack cable and plug in. 

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When you go hunting for these don't be fooled by 1/8" TRS to 1/4" TRS, which are commonly used to adapt headphones with little plugs, to fit larger, standard size, headphone sockets. Those TRS adaptors may work sometimes but there are problems lurking so they should be avoided for standard Eurorack audio. The Eurorack adaptors featured in this article are two-conductor, unbalanced.

EPILOGUE

These adaptors cost me around $1.95 each, in a pack of four (I bought a few packs so I can lose some around my Eurorack synth system ;-). At less than $8.00 for a bag of four, these fit nicely into our "Bargain Studio Hacks" category. I love insanely cheap things which instantly improve your music-life.

Thanks for Reading High on Technology, Good Music To You!

©June 2025 by Mark King, it's NOT ok to copy or quote without written permission from the author. 

Go forth and create beautiful things. . . . . . . . 

Brand new, on the bench

ONE MORE THING -- WHAT ABOUT SIGNAL SIZE LEVEL? Distortion and Headroom

Eurorack systems typically use unbalanced audio, with peaks reaching around +4dBu (there are always exceptions). Pedals designed for guitar processing typically use unbalanced, high impedance audio. 

Signal Levels of Musical Instruments and Audio Interfaces (in dBu)

• Passive Electric Guitars: These produce very low signals, typically ranging from -40 dBu to -20 dBu (10–100 mV). The weak output, driven by pickups and string vibration, needs a high-impedance preamp to boost it for recording or amplification. Pounding power chords on a Les Paul with large humbucking pickups, I measured 5-volt peaks with a VTVM.
• Active Electric Guitars: With battery-powered preamps, these output stronger signals, around 0 dBu to +6 dBu (1–2 volts). This hotter, cleaner signal reduces noise and is ready for direct recording or effects.
• Professional Standard Size Synthesizer Keyboards: These output line-level signals, typically -10 dBu to +4 dBu (0.5–2 volts). They’re designed to connect directly to mixers or audio interfaces for professional recording.
• Line-Level Inputs/Outputs on DAW Interfaces: These operate at standard line levels, either +4 dBu (1.23 volts RMS, pro gear) or -10 dBu (0.316 volts RMS, consumer gear). They handle signals from synths or mixers, ensuring clean integration into a digital audio workstation (DAW). For reference +18 dBu is around 6-volts RMS.

Expressing levels in dBu simplifies comparison: passive guitars are the quietest, active guitars are louder, and synths and DAW interfaces operate at standardized line levels for easy connectivity.

Guitar stomp boxes are typically designed and made to operate somewhere in the range between Passive Electric Guitars and Professional Standard Size Keyboards, some experimentation may be required to find the most compatible stomp boxes. 

Here in the High on Technology studio I've had very good Eurorack synth performance using digital effect pedals (echo, reverb, harmonizer) that require external power supply -- this bigger-than-battery power source usually indicates better headroom and compatibility with the larger signal size presented by Eurorack inputs and outputs.