Wednesday, 1 July 2015

DMFX-1: Open Source Digital Multi-Effects guitar pedal (1)

Rezzonics© presents the most compact digital multi-effects guitar pedal, completely open source, giving you the opportunity to create your own stereo effects or use a huge range of pre-programmed effects.

Every analog or digital effect your guitar needs in one compact format. The best of both worlds: ANALOG for overdrive, distortion, fuzz, octave-up, DIGITAL for echo, delay, chorus, tremolo, phaser, flanger... and many others you can imagine: looper, pitch shift, reverb, leslie...

DMFX-1 main features:
  • TI C55x 16-bit fixed point DSP, providing quality, low power and low cost
  • Dual DSP for low latency, real time signal processing and fully independent Audio and Control processing.
  • Up to two SD/MMC cards for Software and audio data storage
  • One graphical LCD 128x32 pixels Blue with White LED backlight for better visibility
  • Up to 5 configurable LEDs
  • One 5-button display navigator for seamless effect configuration
  • Up to five digitally controlled and configurable potentiometers
  • Analog configurable input distortion (overdrive, crunch, vintage, fuzz...)
  • Analog octave-up effect, mixable with distortion
  • Dual Mono L/R Line Output
  • Stereo Headphones output
  • Guitar Mono Line input
  • Analog input / output buffers and filters
  • Standard +9V DC or USB +5V DC power input
  • Up to 2x USB 2.0 ports (Audio, Control) for PC connectivity
  • Optional USB debugging port XDS100v2, TI Code Composer Studio compatible
  • Foot switch input
  • Compact size: 130 mm x 110 mm x 32 mm (W x D x H)
A stand-alone unit: just plug your guitar, your headphones and configure your desired effect easily via the navigator and LCD menus.

Stereo effects like reverb or speaker rotating effects like leslie can be emulated thanks to the dual mono and stereo outputs.

Analog feel can be emulated thanks to five configurable potentiomenters digitally controlled.

JFET buffer input, low THD distortion, low-voltage, rail-to-rail audio opamps and filters to better adapt guitar signal input and reduce input noise. Exclusive low-cost Schottky diode distortion circuits that emulate germanium clipping diodes.

Analog support for Tuner and Noise compression.

One graphical LCD 128x32 pixels Blue with White LED backlight for better visibility in dark places. A 5-buttons navigator (up-down-left-right-OK) allows easy navigation and effect configuration through menus.

One dedicated audio DSP and one dedicated control DSP provide low latency and real time, while reducing the bill of materials. Control DSP is used for status / commands operations: LCD, buttons and potentiometer control, while Audio DSP is fully dedicated to real time audio effects.

Up to two USB 2.0 (type Mini-B) interfaces allow pedal connection to a PC, for command / status or audio exchange.

Up to two SD/MMC cards can be connected to audio DSP for huge program and audio data storage.

One additional USB (Type-B) interface allows JTAG-Boundary Scan DSP debugging using TI XDS100v2 and Code Composer Studio for implementing your DSP effects.

Open source libraries will offer free digital effect exchange and improvement.

Several assembly options for low cost and high performance scalability.

DMFX-1 is low power, it can be powered by batteries, external +9V DC-DC converter or USB port.

DMFX-1 is compact: Main board + mezzanine board can be packed on a 148 mm x 100 mm x 24 mm enclosure (W x D x H)

Compact size: 148 mm x 100 mm x 24 mm (W x D x H)
3D view of the 2 PCB DMFX-1 guitar pedal (image created with FreeCAD)
DMFX-1 front view showing connectors

DMFX-1 rear view showing USB connectors

DMFX-1 block diagram



  1. intersting project; you are following marshalls well-trodden path
    Several of their amps and delay effects pedals use the DSP card based on a Texas DSP chip
    ( i.e the MG DFX series CFX? EH-1 and RF-1)
    the only differences are the control knobs and the firmware!
    I wonder if the (seperate) eeprom is hackable to roll-your-own DSP?

  2. I had no idea that Marshall used TI fixed-point DSPs. Though they are the older C54 family and they used external SDRAM and I use the newer C55 based on SD/MMC storage and USB.
    The C54 DSP is also used on the Marshall YJM100 for the reverb effect:

  3. Some pictures of Marshall guts showing the DSP, a TMS320VC5401 with SDRAM and EPROM

  4. Seems VERY similar to Axoloti DSP modular synth. GOt a few question:

    1. What is the price range going to be?

    2. What is the programming environment going to be? Pure Data? Or like Axoloti DSP synth; a custom objectbased programming environment?

    3. Can you route audio over USB?

    1. The difference of this kit is that it can work as a standalone system without a PC, it includes graphic LCD, real DSPs, analog distortion, buffers and filters.
      1. I think price range could be between 100$ to 120$
      2. Programming environment is C language on TI Code Composer studio GUI
      3. Yes, audio can be routed over USB

    2. Preamp circuitry is also included as well as line out signal buffers and filters.