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Electro-Harmonix Operation Overlord Allied Overdrive Effect Pedal

For a special overdrive, sometimes you need to call in special forces


by Chris Loeffler

Electro-Harmonix has no less than 45 current production gain-based effects listed on its site, so it’s fair to say they’ve covered a lot of ground in the distortion arena.  As they’ve added one more overdrive effect to their roster, one has to wonder what’s left to cover? The pedal in question, the Electro-Harmonix Operation Overlord Allied Overdrive, answers that question with a unique feature-set.


What You Need to Know


The Electro-Harmonix Operation Overlord Allied Overdrive (we'll call it the Allied Overdrive for short), in addition to being a mouthful, is a stereo overdrive pedal with controls for Gain, Bass, Mid, Treble, and Volume as well as a Boost overdrive with independent volume control and a Dry knob to blend the direct signal with the overdrive. The pedal runs on a standard center-positive 9v power supple, features ¼” stereo inputs and outputs, and true-bypass footswitches for the Overdrive and Boost (more on that later).


The Allied Overdrive uses JFET gain stages to create amp-like, low-to-medium levels of overdrive and early distortion. It's relatively uncolored, and can be dialed in via the three-band EQ controls to sound identical to the direct signal. The Gain control runs from completely clean to about as much crunch and saturation as a cranked vintage amp, with minimal compression. I found the Treble, Mid, and Bass controls to provide a useful range of sounds without going overboard at the extremes. Although the shape of the distortion changes with the EQ, the basic character of the tone does not… it isn’t an amp in a box, it gives amp-like distortion to complement the core tone.


The Boost adds cleanish overdrive boost in front of the Overdrive to up the gain (as opposed to after, where it would just make it louder). I say “cleanish” when describing the boost because there is a bit of a push in the mids to the boosted signal along with a touch of gain, similar to a tame Tube Screamer. The pedal comes from the factory with the Boost side tied to the Overdrive so both are tied to the bypass switch. An internal DIP switch decouples the two, so they can run independently.


Input Level control selects between High (HI), Normal (NORM), and Low (LO) input settings, so anything from extremely low output guitar pickups to a hot synthesizer output can be accommodated. Using hotter, modern pickups in the LO input setting resulted in an appropriately vintage sag, while slamming the overdrive with the same pickups in the HI input setting gave an extremely aggressive girth to the distortion.


Dry control blends the direct (clean) signal into the overdrive, which gives players the ability to dial in a little definition and clarity from the direct signal. Combining the Dry with the Overdrive, the Volume control makes available a large dB boost for players looking to use the overdrive signal to push their preamps.


In addition to mono and stereo uses, the Overlord can split a mono input into a stereo output to send the signal to two amps.




The Boost cannot be placed after the Overdrive.




The Electro-Harmonix Operation Overlord Allied Overdrive is an incredibly flexible effect tool that marries well with any instrument you can put in front of it, offers the unique feature of stereo ins and outs, and is as transparent a gain device as you can find.  -HC-




EHX Operation Overlord Allied Overdrive Product Page


The Allied Overdrive is available for about $150 "street" from:




Musician's Friend

Guitar Center

Sam Ash



Gear Tree





Chris Loeffler is a multi-instrumentalist and the Content Strategist of Harmony Central. In addition to his ten years experience as an online guitar merchandiser, marketing strategist, and community director he has worked as an international exporter, website consultant and brand manager. When he’s not working he can be found playing music, geeking out on guitar pedals and amps, and brewing tasty beer. 


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