MPG-50 Programmer Unassembled DIY Kit

MPG-50 Programmer Unassembled DIY Kit

Regular price $330.00 Sale

This listing is for an unassembled MPG-50 kit.  The kit includes:

  • Bare PCB
  • All sliders, pots, knobs, hardware, jacks, power jacks
  • All SMD components and CPU
  • DC adapter (Available in North American, UK, and EU receptacle types)
  • Steel enclosure with screw-on rubber feet
  • OLED screen
  • Schematic & BOM
  • Software installation file download

This kit requires that all jacks, pots, sliders, and screen are soldered on to the PCB, and the PCB gets mounted into the enclosure.   This kit requires surface-mount soldering.   The CPU must be programmed with an ISP programmer such as USBasp.   A batch file for one-step programming of bootloader, EEPROM, and main OS will be provided to people purchasing this item.  This is not a beginner level kit.  It requires SMD soldering.  The parts used are 0603, 0805, and 1206 passives, and TQFP-48 processor.  This kit should be built by experienced builders only.  The build guide is not a step-by-step guide.  It is intended to give the builder important notes about component orientations, LED orientations, and mounting the screen, but it assumes that the builder has sufficient experience with BOMs, pcb assembly, SMD soldering, and good construction skills.  Please don't purchase this kit if you're a novice intending to save money!


 User's Manual V1.31

User's Manual V1.35 (Latest edition)

Build Guide

Retroaktiv MPG-50 is a fully featured MIDI programmer for the popular Roland Alpha Juno 1 and 2, and the MKS-50 rackmount synthesizer.  The MPG-50 is a compact 370mm (14.5") x 149mm (6") x 40mm (1.5").   It features 37 sliders and knobs which control all of the features included on the original PG-300 plus more.   The unit is housed in a powder-coated metal enclosure. 


Behringer BCR2000 Roland PG-300 Retroaktiv MPG-50
Control of all Alpha Juno tone parameters Yes Yes Yes
Control of MKS-50 patch menu parameters Yes No Yes
Ability to create and save custom CC maps for other synths Yes No Yes
Control 2 synths independently from one unit simultaneously No No Yes
CC to SYSEX translation No No Yes
Ability to control any AJ/MKS50 params with mod wheel, breath, aftertouch No No Yes
Intelligent patch generator No No Yes
Manual mode (transmit position of all sliders) No Yes Yes
Screen that shows parameters being edited, not just numbers No No Yes
Firmware can be updated in the field with MIDI Yes No Yes
Assignable controls that can control many params at once No No Yes
Assignable foot pedal No No Yes
Ability to select AJ programs from the controller Yes No Yes
Soft MIDI THRU Yes No Yes
Scratch Patch Generator No No Yes
MIDI filtering and MIDI data mapping No No Yes

The MPG-50 has full MIDI implementation, allowing for MIDI messages to be passed through to the Juno while also sending parameter control data.  Each Juno sysex parameter can be controlled using MIDI CCs, which allows for slider movements to be recorded on a DAW.  Also featured are an expression pedal input, and two AUX sliders, each of which, can be programmed to control up to 5 parameters simultaneously.  The range and polarity of each ASSIGN parameter is programmable, allowing for a slider to do something like open the filter, slightly increase the DCO LFO rate and amount, and change the attack setting all with one slider or pedal.   

Each slider can have a CC # assigned to it, allowing the MPG-50 to control any synth that can respond to CC messages.

MPG-50 will allow incoming breath, mod wheel, and aftertouch messages to be routed to any 5 Juno parameters each.  

A patch generator function allows for users to create new "scratch" programs (basic programs that serve as a starting point for creating sounds), a random patch generator, a manual function (transmits the position of all 39 front panel parameters),  as well as a user configurable random generator that will randomize only parameters selected by the user.  The patchgen menu features the following:

Random Tone Generator - Features multiple random categories, such as basses, polyphonic comp, bells/metal, percussion, pads, synth brass, strings, drones, noise FX, or completely random.  The following sections of the synth can be selected to not be randomized (masked):  DCO wave/level, DCO pitch mod, VCF level/rez, filter mod, VCA mod, chorus, LFO, Env times (T1, T2, T3, T4, Follow) and Env levels.  (L1, L2, L3)  The amount of randomness can also be dialed in, making the random tone generator on the MPG50 a powerful creative tool.  

The MPG50 features 2 controller channels, MAIN and AUX.  Users can switch between the MAIN and AUX channels to control multiple Alpha Juno/MKS50 synthesizers separately, or simultaneously.  This feature allows two Junos to be seamlessly combined to create a 2 DCO "super Juno".   When both synths are selected, the MASTER VOLUME fader on the MPG becomes a cross-fade control that fades between the two Junos, making controlling 2 Junos or MKS50s feel like an integrated "super Juno".  

HOLD feature will sustain all notes played on the Juno until HOLD is disabled.

3 assignable controllers (CTRL A, CTRL B, and Expression pedal) can be configured to control up to 5 Juno parameters each.  Control range for each parameter can be set, and the controls can be inverted for each parameter.  Each ASSIGN has a factory default as well as a user preset, allowing for 6 ASSIGNs, alll of which can be recalled with a button press.  Incoming mod wheel and aftertouch MIDI messages can be routed to ASSIGN A and ASSIGN B, allowing for up to 5 parameters to be controlled with each.  

MIDI preferences can be saved with a button press, eliminating the need to reconfigure your settings on power up.  

The unit can be set to transmit MIDI CC messages and sysex simultaneously, allowing for the MPG-50 slider movements to be recorded and played back on  DAW.  The MPG-50 will translate the recorded CC messages to juno sysex when the DAW plays the recorded CC track into the MPG-50.  Any incoming note, aftertouch, mod wheel, pitch wheel etc is automatically passed through the MPG-50 to the Juno.  Any CC messages can be translated into Juno sysex.

In the main menu, users can select MONO or POLY mode, adjust bend range,  and save and recall AUX/Pedal assignment settings.  For MKS-50 synths, there is a patch menu giving access to : Detune, transpose, upper range, lower range, tone number, and modulation sensitivity.

All menu information is displayed on a compact OLED screen, allowing for deep editing and the display of parameter values being transmitted.  

MPG-50 offers all of the functionality of the original PG-300, plus a suite of modern performance and MIDI features that make this the most full featured Alpha Juno programmer on the market.