The Mod Duo is a digital multi-effects pedal made by MOD Devices, a German company. Released in 2014, it is a Linux-based, open-source effects unit: instead of a fixed set of built-in sounds, it runs free plugins from a shared library, and you build pedalboards by dragging them together in a web browser123. It is no longer manufactured, but MOD Audio still supports it4.
Under the hood it is a DSP engine: a dual-core ARM A7 running at 1.0 GHz with 1GB of RAM and 4GB of flash storage, on a stripped-down version of Linux25. MusicRadar summed up the concept as "a thoroughly modern combination of DSP power and interface simplicity that provides a wealth of quality processing for musicians"2.
Plugins and browser editing
The Mod Duo has no editing software to install and no menu-diving on the pedal itself. Sound editing is carried out through an internet browser using a local IP address, over a USB connection that can be wired or wireless2. You build a virtual pedalboard on screen, and the Duo runs it.
The plugin library is the heart of the system. MOD Audio lists over 400 plugins readily available for free, with new releases every month1. The modules use the LV2 format, which Bass Gear Magazine's reviewer noted is "not proprietary and able to be developed for by anyone"9. Users can also browse other people's pedalboard ideas and download them instantly to the Duo, so the community's boards work as ready-made presets10.
What that means in practice is that the Duo can cover the whole range of effect types, from overdrive and distortion to delay, reverb, chorus and beyond, with amp sims included. Performer Mag's reviewer found that "The Overdrives and distortions act like the real thing; they don't get fuzzy, fizzy or tinny," and that the amp sims were flexible without wading through parameters11.
The controls
The Duo's front panel is deliberately minimal: two backlit LCD screens, two footswitches and two selector knobs in a die-cast aluminum casing27.
- Footswitches: switch entire presets, pedalboards, tap tempo, or bypass the unit1
- Multi-function knobs: any plugin parameter can be assigned to either knob, and several controls can be stacked on each knob, cycled with a push1
- Screens: two backlit LCDs showing what is running and what is assigned2
The two knobs are the main limitation for players who like to tweak with their feet or hands mid-song, and it is the main thing its successor addresses1212.
Power and connections
The Duo is built as a stage unit with a full connection set15:
| Connection | Detail |
|---|---|
| Inputs | Two independent 1/4" TS jacks with digitally controlled analog multi-stage pre-amplification7 |
| Outputs | Usable in balanced or unbalanced mode1 |
| MIDI | Full support, both legacy 5-pin DIN and USB1 |
| USB host | USB 2.0 Standard A-type, supporting USB Wi-Fi and USB MIDI5 |
| USB device | USB 2.0 Standard B-type, supporting a USB Ethernet adapter5 |
| Control-Chain | RJ-45 port for MOD's control chain5 |
| Headphones | Output with independent digital volume control5 |
| Audio codec | Cirrus Logic low-noise codec5 |
Power comes from an internal supply rated 100V to 240V at 50 to 60 Hz, so the same unit works in every country without a step-up transformer1. That means it is a mains-powered unit rather than one that runs on a typical pedalboard power supply.
Where it came from
MOD Devices had a product on the market back in 2013 called the MOD Quadra, and the Mod Duo is an evolution of that earlier unit13. The Duo itself launched in 2014, created with the help of free software developers3. At its 2016 launch, pricing per piece started at US $6497, and Premier Guitar's review put street price at $6508. Alongside the standard die-cast aluminum casing, several hardware chassis were in development at one point, from aluminum enclosures to transparent polycarbonate versions13.
The Mod Duo X and what came after
In 2018 MOD Devices introduced the Mod Duo X, a more powerful version of the Duo in a desktop format aimed partly at electronic musicians614. Where the Duo is a floor pedal with two footswitches and two knobs, the Duo X is a standalone stereo unit with far more physical control1215.
| Mod Duo | Mod Duo X | |
|---|---|---|
| Format | Floor pedal7 | Desktop unit14 |
| Processor | Dual-core ARM A7 1.0 GHz5 | Quad-core ARM Cortex-A53, 1.5 GHz6 |
| Controls | 2 footswitches, 2 assignable knobs12 | 2 encoders, 8 potentiometers, 4 pads or buttons, all assignable614 |
| Displays | 2 backlit LCDs2 | 2 large screens showing control assignments in real time12 |
| Extra I/O | Control-Chain RJ-455 | EXP/CV in and out, S/PDIF out, MIDI I/O9 |
Performer Mag described the Duo X as "adding in some extra real time control," with its four soft-touch buttons also able to engage or disengage effects1215. Both units share relay-based true bypass and the same browser-based editing and plugin ecosystem16.
The Duo and Duo X now sit on MOD Audio's legacy devices page, no longer manufactured but still supported4.
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Questions
Is the Mod Duo still made?
No. MOD Audio lists the Mod Duo among its legacy products that are not manufactured anymore, but the company still supports it. Units can be found second-hand, and the plugin library and browser-based editing continue to work for existing owners.
Is the Mod Duo open source?
Yes. The Mod Duo runs a Linux-based open source system, and its effects modules use the LV2 plugin format, which is not proprietary and can be developed by anyone. That is why the plugin library has grown with free community contributions rather than paid expansions.
Does the Mod Duo have MIDI?
Yes, and in both forms. The Mod Duo offers full MIDI support over legacy 5-pin DIN connections and over USB. Its USB host port also accepts USB MIDI devices, so class-compliant MIDI controllers can be plugged straight in.
Does the Mod Duo have true bypass?
Yes. MOD Audio specifies relay-based true bypass for the Mod Duo, so when the unit is bypassed the signal passes through physical relay contacts rather than the digital converters.
What is the difference between the Mod Duo and the Mod Duo X?
The Mod Duo X is a more powerful successor in a desktop format aimed partly at electronic musicians. It moves from the Duo's ARM A7 processor to a quad-core ARM Cortex-A53 running at 1.5GHz, and adds ten assignable controls, two encoders, eight potentiometers and four pads, against the Duo's two knobs and two footswitches.
Can the Mod Duo run amp sims?
Yes. The Mod Duo's plugin library includes amp simulation among its hundreds of free effects, and Performer Mag's reviewer found the amp sims flexible without needing to wade through parameters. Overdrives and distortions were described as acting like the real thing.
Sources (15)
- MOD Duo - MOD Audio website, mod.audio, 2023-06-01
- MOD Duo review, MusicRadar, 2018-09-17
- MOD DEVICES announces the MOD Dwarf: the compact, affordable, and endlessly customizable modular effects processor, MusicPlayers.com, 2020-02-27
- Legacy Devices, MOD Audio (mod.audio), 2023-06-01
- NAMM 2017: Is the MOD Duo open-source multi-effects 'the definitive stompbox'?, MusicRadar, 2017-01-12
- MOD Devices Presents the MOD Duo X, Premier Guitar, 2018-06-14
- MOD Devices Launches the MOD Duo, Premier Guitar, 2016-12-07
- MOD Duo Review, Premier Guitar, 2017-10-13
- Mod Devices, Bass Gear Magazine, 2020-05-26
- Amp simulator: is it worth using this feature?, MOD Audio, 2021-03-24
- Mod Duo Pedal Review, Performer Mag, 2018-09-13
- Mod Duo X REVIEW, Performer Mag, 2020-01-28
- MOD Duo - A Linux-based open-ended effect system in a pedal, gearnews.com, 2016-07-24
- NAMM 2019: MOD Duo X open-source hardware effects unit, gearnews.com, 2019-01-29
- MOD Devices Duo X, Delicious Audio, 2019-01-25
