KRM Music Systems
KRM Music Systems

Keith Robert Murray . com

[MIDI-CV-Arpeggiator] [Synth Repair] [Music And Demos]View On Your Mobile Device

MIDI-CV-Arpeggiator Retrofit

MIDI-CV-Arpeggiator Retrofit

MIDI-CV-Arpeggiator Retrofit

Update the Functionality of your Monosynth

The KRM MIDI-CV-Arpeggiator updates your monosynth with an arpeggiator, mini sequencer, additional LFO, portamento with 2 modes, multi-trigger, and other functions that modern electronic music producers expect. Use the mini sequencer to program your own arpeggiator pattern, or select one of the 7 built-in ones. Create 2 custom LFO shapes, in addition to the 9 standard shapes already included. The arpeggiator, mini sequencer, and LFO can be synced via MIDI.

Major Support

The MIDI-CV-Arpeggiator supports all major CV standards, including 1V/oct, Hz/volt, Buchla or EML (1.2V/oct), and EMS (0.32V/oct). Gates can be configured as S-Trig or V-Trig, with a low (5 volt) or high voltage gate.

The board is small, 75x48 mm (2 15/16" x 1 7/8"), to fit into most synths. It requires a DC power source between 10 and 20 volts.

MIDI Control, And Then Some

The MIDI-CV-Arpeggiator has an extensive list of real-time performance controls. Now you can use all of those buttons and knobs on your MIDI controller, to get the most out of your vintage monosynth.

Real-Time MIDI Control

  • Arpeggiator On/Off
  • Arpeggiator Note Latch On/Off
  • Arpeggiator Pattern Select (7 built-in, plus 1 programmable)
  • Custom Arpeggiator Pattern Record
  • Arpeggiator MIDI Clock Sync On/Off
  • Arpeggiator Speed and MIDI Beat Quantization
  • Arpeggiator Gate Width
  • Aux CV (Filter) Control
  • LFO MIDI Clock Sync On/Off
  • LFO Speed and MIDI Beat Quantization
  • LFO Waveshape Select (8 built-in, plus 2 programmable)
  • LFO Phase
  • LFO Key-down Restart On/Off
  • MOD Wheel Mapping (pitch or aux CV)
  • MOD Wheel Bend Range (in semitones, when in pitch mode)
  • Pitch Wheel Bend Range (in semitones)
  • Portamento On/Off
  • Portamento Mode (constant speed, or constant rate)
  • Portamento Speed

Arp/Sequencer and LFO MIDI Sync

  • 4 Whole Notes
  • 3 Whole Notes
  • 2 Whole Notes
  • Whole Note
  • Half Note
  • Half Note Triplet
  • Quarter Note
  • Quarter Note Triplet
  • Eighth Note
  • Eighth Note Triplet
  • Sixteenth Note
  • Sixteenth Note Triplet
  • Thirty-second Note
  • Thirty-second Note Triplet

LFO Waveshapes

  • Triangle
  • Saw
  • Inverted Saw
  • Square
  • 40% Pulse
  • 30% Pulse
  • 20% Pulse
  • 10% Pulse
  • Random
  • Programmable 1
  • Programmable 2

Additional MIDI Arpeggiator Output

In addition to the CV, gate, and aux outputs, the board has a dedicated MIDI output. All note data, including the arpeggiator and mini sequencer, is echoed to the MIDI output.

You can chain MIDI devices together, or run the arpeggiator and mini sequencer output to a MIDI synth module. Note velocity, pitch bend, and mod wheel messages can be sent as well.

Custom Tuning Table for Fine-Tuning, or Microtonal Scales

Does your synth have tuning issues at the extreme high or low range? Do you have a DIY VCO that doesn't conform to the standard V/octave or Hz/volt tuning systems? Do you want to experiment with microtonal scales?

The MIDI-CV-Arpeggiator has a dedicated custom tuning table. Each semitone in the table can be fine-tuned to match your VCO response, or to create any arbitrary scale.

The custom tuning table can be toggled on and off, to quickly switch between standard and custom tuning.

Easy Configuration via the Learn Button

All basic configuration can be done through the Learn Button, and your MIDI controller. This includes...

Learn Button Configuration

  • MIDI Channel
  • Coarse and Fine Tuning
  • Aux CV Mapping (Wheel, Knob, Button, or Key Velocity)
  • Pitch CV Response (1V/oct, 1.2V/oct, 0.32V/oct, Hz/volt)
  • V-Trig or S-Trig
  • Low or High voltage Gate
  • Multi-trigger On/Off
  • Aux CV Inversion On/Off
  • Custom Tuning Table (for microtonal scales, or DIY projects)

Advanced Control for MIDI Experts

Are you a MIDI freak? Do you dream of SysEx?

Take total control of the MIDI-CV-Arpeggiator configuration. Set the power-on defaults to suit you. Create LFO shapes that track pitch to make exact intervals. Modify the anti-zipper settings to give your MIDI knobs and faders the perfect feel. Define custom tuning tables for exotic scales. Enable or disable Active Sense, All Notes Off, and Reset All Controllers messages, to make all of your MIDI devices play nicely together. Re-map any real-time function to any MIDI CC knob, fader, or button.

There are 55 configuration settings to play with, in addition to the custom arpeggiator pattern, mini sequencer memory, 2 custom LFO shapes, and the custom tuning table.

Technical Specifications

Technical Specifications

  • 10 to 20 V DC power source.
  • 30 mA current draw.
  • Size 75x48 mm (2 15/16" x 1 7/8"). Approximately 12 mm deep (1/2"), without mounting hardware.
  • 5-pin DIN MIDI input and output (MIDI jacks not included).
  • 0 to 5 V output for pitch and aux CV.
  • 1V/oct, 1.2V/oct, 0.32V/oct, or Hz/volt pitch CV response.
  • S-Trig or V-Trig gate.
  • 5 V gate, or high voltage gate (equal to the DC source voltage).


MIDI-CV-Arpeggiator Retrofit Manual 1.8 MB
MIDI-CV-Arpeggiator Quick Reference Card 239 kB

Purchase via PayPal

USD$219 Shipping Included, Anywhere In The World


The KRM MIDI-CV-Arpeggiator Retrofit comes with a 90 day replacement or refund warranty valid only for original parts and workmanship, and does not apply to products which have been subject to misuse. The warranty period starts at the product delivery date.

MIDI-CV-Arpeggiator Retrofit - Music Demo

MIDI-CV-Arpeggiator Retrofit - Music Demo

MIDI-CV-Arpeggiator Retrofit - Tech Demo

MIDI-CV-Arpeggiator Retrofit - Tech Demo