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All the MOD units run a highly-optimized Linux embed system, using JACK as audio server and loading plugins in LV2 format.
Plugin parameters can be controlled via the units' built-in knobs and footswitches, via MIDI CC and Pitchbend or via Control Chain devices.
They can also be modulated with CV output ports, either provided by a plugin or the Duo X physical inputs.

Technical information

The MOD Duo runs the Linux kernel version 5.10, running in a ARMv7 32bit OS built with GCC4.9 and glibc 2.21.
The MOD Duo X runs kernel version 4.4, in a ARMv8a 64bit OS built with GCC4.9 and glibc 2.21.
The MOD Dwarf runs kernel version 5.10, in a ARMv8a 64bit OS built with GCC7.5 and glibc 2.27.
All units have the real-time patch applied for the kernel build.

ALSA is used for the i2s audio driver.
JACK runs inside as audio server backend, with mod-host loading each LV2 plugin as a new (internal) JACK client.
mod-ui is the web server, it talks to mod-host over a unix socket.
mod-ui is the one that owns the loaded project/session, with mod-host acting as a dumb host that only does as commanded.

There's no X11 or any other kind of graphical interface. In fact, X11 libs are not even available.

SSH is open by default.

The MOD Duo CPU is a dual-core Cortex A7, running at a constant 912 MHz.
The MOD Duo X CPU is a big-little 4x Cortex A53 and 2x Cortex A72, with the A53 cores running at 1.4GHz and the A72 cores running at 1.6GHz (constant values).
The MOD Dwarf CPU is a quad-core Cortex A35, running at a constant 1.3GHz (or 1.2GHz if "ground loop noise reduction" mode activated).

The compiler is GCC 4.9 on Duo and Duo X, GCC 7.5 on Dwarf.

The default compilation flags for the Duo are:

-O3 -mcpu=cortex-a7 -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard -mvectorize-with-neon-quad

For the Duo X the flags are:

-O3 -mcpu=cortex-a53 -mtune=cortex-a53

And for the Dwarf:

-O3 -mcpu=cortex-a35 -mtune=cortex-a35

(Note: 64bit ARM compilers do not use 'fpu' flags, as their usage is implied)

For aggressive optimization, add these:

-ffast-math -fprefetch-loop-arrays -funroll-loops -funsafe-loop-optimizations

Building binaries for them can be easily done using the mod-plugin-builder.

Apart from programming software in a "traditional" way, it's also possible to generate audio plugins for the MOD from gen~ objects created in Cycling '74 Max. See the Max_gen~ page for more details.

Plugin Development

See the dedicated Creating Audio Plugins page for this topic.

Building plugins can be done with mod-plugin-builder.


The mod-plugin-builder is a custom build system that gives developers a similar system to what's available inside the MOD units.
We do not recommend the use of a regular Linux ARM system or compiler, as it might lead to issues due to mismatching library versions.

If you're running Linux just clone MOD Plugin Builder and follow the instructions.
For other operating systems you will need something like docker desktop, more details here.

In summary:

$ git clone
$ cd mod-plugin-builder
$ ./ <platform>
$ # Where platform can be modduo, modduox or moddwarf
$ # NEW: You can use modduo-static or modduox-static as platform if GCC4.9 is too old, these special targets will use GCC7.5 similar to the Dwarf

This process should take at least 1 hour, probably more depending on your CPU.
If you are lacking on time or disk space (needed ~15G) you can use "minimal" as argument after the platform which will only build the compiler and the bare minimum libraries.

Assuming your source code is cross-compilation friendly (ie, no hardcoded compiler and paths and uses pkg-config to find extra libraries), the compiler setup is as simple as: (adjust as needed)

$ pushd ~/mod-plugin-builder/
$ source local.env <platform>
$ popd
$ # cmake, waf configure, ./configure, etc
$ make

The local.env file will setup your Linux compiler environment variables (such as CC, CXX, CFLAGS, etc) to use mod-plugin-builder files.
If everything goes well, the resulting binaries will be compatible with the target platform.

Quick example plugin

A quick example plugin is available inside mod-plugin-builder in plugins/package/eg-amp-lv2/source/, which works with this cross-compilation setup.

Building this example plugin can be done like so: (adjust as needed)

$ cd ~/mod-plugin-builder/
$ source local.env modduo
$ cd ~/mod-plugin-builder/plugins/package/eg-amp-lv2-labs/source/
$ make

After this the eg-amp.lv2 bundle is ready to be deployed into a MOD unit.

Deploying plugins

You can push an LV2 plugin bundle to a MOD unit via command-line, using curl, by running this: (adjust as needed)

$ cd ~/mod-plugin-builder/plugins/package/eg-amp-lv2/source/
$ tar cz eg-amp.lv2 | base64 | curl -F 'package=@-'

That's it! Your plugin is now inside the unit!

To those curious ones, the last command packs the eg-amp.lv2 into a tar.gz file, encodes it as base64 and then sends it to a special URL that the MOD unit uses to install plugin tarballs.

APIs and Documentation


Audio and MIDI plugins in MOD Devices are done in LV2 format.
MOD provides custom LV2 extensions (for MOD specific data and HTML interfaces).

See our LV2 page for more information on how LV2 is integrated in MOD.

For reference/external information see:


Also known as Jack Audio Connection Kit, is the audio server running inside the MOD.
Developers can create JACK clients to interact with the audio data directly (without being managed by a plugin host).

For more information see:

NOTE: All MOD units use JACK2.


Being Linux, developers have access to UNIX and POSIX APIs.
This means <unistd.h>, <pthread.h> and <stdlib.h> for example.

For more information see:


As of release 1.10, the MOD Duo and MOD Duo X uses:

  • GCC 4.9
  • glibc 2.21
  • binutils 2.25

While the MOD Dwarf uses:

  • GCC 7.5
  • glibc 2.27
  • binutils 2.26.1

Note: Within mod-plugin-builder you can use "modduo-static" or "modduox-static" as platform to get GCC7.5 and binutils 2.26.1.
The glibc version will remain the same though, for backwards compatibility.


The following libraries are available inside the MOD units:

  • acl
  • alsa
  • armadillo
  • audiofile
  • boost
  • cairo
  • dbus
  • expat
  • fftw/fftwf (v3.3.5 on Duo, v3.3.8 on Duo X and Dwarf)
  • ffmpeg
  • flac
  • fluidsynth
  • fontconfig
  • freetype
  • gio/giomm
  • glib/glibmm
  • glibc (v2.21)
  • icu
  • jack2
  • libffi
  • libgig
  • libjpeg/libturbojpeg
  • liblo
  • libogg
  • libpng
  • libsamplerate
  • libsigc
  • libsndfile
  • libvorbis
  • libxml2
  • lilv
  • lvtk (v1 and v2)
  • mxml
  • ncurses
  • ne10
  • pcre
  • pixman
  • python (v3.4)
  • qt5 (core, network, sql and xml)
  • readline
  • sdl
  • serd
  • sord
  • sratom
  • systemd (v219)
  • zita-convolver
  • zita-resampler

Developer mode

MOD's web interface has some hidden features, not really useful for users but useful for developers.
This includes:

  • Buffer size change (128 or 256 frames per cycle)
  • Install-All button in plugin store
  • Network statistics
  • Xrun counter (a.k.a. audio drop-outs)

Developer mode can be enabled on the settings page:

Useful links

These are useful links for general information regarding developing audio plugins and realtime software.

Please note that it is also possible to build LV2 plugins using DPF or Juce. Building with those frameworks is not yet documented though, please reach out to us if interested on the subject.

USB Device Support

  • Most USB-MIDI devices (if they are class-compliant, they should just work)
  • Arduino running MocoLufa firmware (to create midi-controllers)
  • PlayStation 3 and 4 Controllers
  • Guitar Hero Controller (Red Octane Xbox version)
  • Any regular joystick

Hardware Specification



  • Dual Core ARMv7 1.0GHz
  • 4GB Flash Storage, 1GB RAM


  • Cirrus Logic, 24 bit / 48 kHz AD/DA
  • DAC/ADC: 104dB Dynamic Range. -90dB THD+N


  • 2 knobs with LCD screen
  • 2 foot switches with color LEDs


  • MIDI IN/OUT – Standard DIN 5 pins
  • Control Chain – RJ45 connector – for additional controllers
  • USB HOST – USB 2.0 Standard-A type, supporting: USB Bluetooth and USB MIDI
  • USB DEVICE – USB 2.0 Standard-B type, supporting: USB Ethernet Connection



  • A53 quad core 1.4 GHz + A72 dual core 2 GHz
  • 16GB Flash Storage, 2GB RAM


  • Cirrus Logic, 24 bit / 48 kHz AD/DA
  • DAC/ADC: 104dB Dynamic Range. -90dB THD+N


  • 2 knobs with LCD screens
  • 7 push buttons with color LEDs
  • 8 analog potentiometers


  • MIDI IN/OUT – Standard DIN 5 pins
  • Control Chain – RJ45 connector – for additional controllers
  • USB HOST – USB 2.0 Standard-A type, supporting: USB Bluetooth and USB MIDI
  • USB DEVICE – USB 2.0 Standard-B type, supporting: USB Ethernet Connection
  • Control Voltage IN/OUT – 0 to 10 volt – for connecting to analog gear
  • SPDIF output – 3.5mm-jack – for digital audio output