Pricing and availability

We compare 600+ stores and found this item at 9 stores. Prices updated .

Sweetwater
3.5 (11)
$49.00
Amazon
3.5 (67)
Used
Reverb
5.0 (4)
$82.11 2 available New
Musician's Friend
4.0 (3)
$39.00
zZounds
5.0 (1)
$49.00
B&H
5.0 (3)
$49.00
Thomann
4.3 (57)
$68.00

Price History

Based on price data from 4 merchants for "Keith McMillen Instruments MIDI Expander". Prices shown reflect NEW condition. Tracking began Apr 2, 2026.

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Description

Unleash the full potential of your Keith McMillen Instruments (KMI) controllers with the MIDI Expander. Designed to bridge the gap between your favorite KMI devices such as the SoftStep, 12 Step, QuNeo, QuNexus, and K-Mix, and your cherished MIDI hardware, this expander is the key to elevating your performance and production setup. With its straightforward functionality, it transforms class-compliant MIDI data from your USB-connected KMI controller into conventional 5-pin MIDI I/O, allowing seamless communication with your MIDI-equipped synths and effects modules.

The MIDI Expander is the perfect solution for musicians looking to extend the capabilities of their KMI controllers beyond the digital realm, into the vast universe of MIDI hardware. It's all about making connections simpler, more effective, and entirely fuss-free. Whether you're on stage or in the studio, this device ensures that your creative workflow is never hindered by technical limitations. True plug-and-play operation, coupled with bus-powered convenience, means you're always ready to go, with or without a computer. LED indicators provide instant visual feedback on power and MIDI activity, ensuring you're always in control.

Designed with the modern musician in mind, the MIDI Expander is not just another accessory; it's an essential tool for pushing the boundaries of what's possible with your KMI gear.

Key Features:

  • True plug-and-play operation with class-compliant MIDI over USB to conventional 5-pin MIDI conversion
  • Completely bus-powered, eliminating the need for external power supplies
  • LED indicators for power, MIDI in, and MIDI out activity, ensuring full control and monitoring
  • Enhances connectivity between KMI controllers (SoftStep, 12 Step, QuNeo, QuNexus, and K-Mix) and MIDI hardware devices
  • Compact and rugged design, built for the rigors of live performance and studio work
  • No computer required for fully standalone operation

Product specs

Type MIDI Expander
Ports In/Out
Other I/O 1 x USB Type A
Compatibility Keith McMillen SoftStep, 12 Step, QuNeo, QuNexus, K-Mix
Power Supply 1 x USB Type B

FAQs

What devices are compatible with the Keith McMillen Instruments MIDI Expander?

The Keith McMillen Instruments MIDI Expander is compatible with Keith McMillen products such as SoftStep, 12 Step, QuNeo, QuNexus, and K-Mix.

What type of power supply does the KMI MIDI Expander require?

The KMI MIDI Expander requires a USB Type B power supply for operation.

How does the Keith McMillen Instruments MIDI Expander connect to other devices?

The MIDI Expander connects to other devices using MIDI In/Out ports and includes a USB Type A port for additional connectivity.

Can the KMI MIDI Expander be used with non-Keith McMillen MIDI controllers?

The KMI MIDI Expander is specifically designed for use with Keith McMillen products, and compatibility with non-Keith McMillen controllers is not guaranteed.

What is the primary function of the Keith McMillen Instruments MIDI Expander?

The primary function of the Keith McMillen Instruments MIDI Expander is to provide additional MIDI connectivity for compatible Keith McMillen products, allowing for expanded control and integration.

sonicstate

sonicstate

Keith McmIllen 12 Step Foot Control Keyboard

Video thumbnail for Keith McmIllen 12 Step Foot Control Keyboard by sonicstate

Keith McmIllen 12 Step Foot Control Keyboard

sonicstate

sonicstate

Video thumbnail for K-MIX by Keith McMillen #1 ("No Computer" mode) by True Cuckoo

K-MIX by Keith McMillen #1 ("No Computer" mode)

True Cuckoo

True Cuckoo

Video thumbnail for Sonic LAB -  Quneo 3D MIDI Controller - Keith Mc Millen Instruments by sonicstate

Sonic LAB - Quneo 3D MIDI Controller - Keith Mc Millen Instruments

sonicstate

sonicstate

Video thumbnail for SoftStep Demo- note out via MIDI Expander by Muse Kinetics

SoftStep Demo- note out via MIDI Expander

Muse Kinetics

Muse Kinetics

Reviews

PROS

  • Seamless integration with KMI gear like the 12-Step and SoftStep

  • Lightweight design, easy to transport

  • Provides power to KMI devices without a computer

  • Simple setup, functions invisibly

  • Enables connection between USB MIDI devices and DIN MIDI devices

CONS

  • Only compatible with specific Keith McMillen products

  • Feels overpriced for its basic construction

  • Flimsy build quality raises durability concerns

  • Requires separate purchase to fully utilize KMI products

  • MIDI ports may not align well with some cables

  • Doesn't offer MIDI thru or USB to MIDI conversion

  • Mini USB connection is awkward for foot controllers

  • Limited to expanding only certain KMI devices

Owner Insights

We analyzed real musician discussions from forums and Reddit to find what players love, question, and tweak about Keith McMillen Instruments MIDI Expander.

Features and functionality

  • The Keith McMillen MIDI Expander includes a MIDI IN, while the MIDI Out Adapter Cable only supports MIDI OUT, making the Expander more versatile for complex setups.

    Source
  • The tilt and pressure assignability provide unique control options, but some users find the pitch bend nub not very practical.

    Source

Comparisons

  • The Kenton MIDI USB Host, particularly the MK2 and MK3 models, is often compared to the Keith McMillen MIDI Expander for similar functionality.

    Source

Use cases and applications

  • The MIDI Out Adapter Cable is suggested for simpler setups where only MIDI OUT is required, making it an economical choice at $14.

    Source
  • Ideal for rhythmic and non-velocity synth tasks, often used as a bassline synth controller or for chopping/stuttering effects.

    Source

User experience

  • Users report confusion about why the Keith McMillen 12-Step lacks a built-in 5-pin MIDI output, necessitating additional adapters or expanders.

    Source
  • Velocity response is inconsistent, which may affect its use for dynamic playing, but it's suitable for rhythm-focused tasks.

    Source

Software and compatibility

  • Compatibility issues noted with the Kenton MIDI USB Host when used with certain devices like the SoftStep 2 and Microcosm pedal, highlighting potential limitations.

    Source
  • CV connectivity is highlighted as a strong feature for those integrating with hardware setups.

    Source

Build quality

  • The QuNexus is noted for its durability, being described as nearly indestructible and ideal for portability, particularly for use in casual settings like coffeehouses.

    Source

4.5 out of 5

Based on 0 Reviews and 2 Ratings

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Artist usage

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See how Rick Smith uses Keith McMillen Instruments MIDI Expander

Rick Smith

Music Producer

Freur

...
Verified via Photo

This image posted to Underworld's Instagram account shows Rick Smith's portable Eurorack setup. The McMillan MIDI Expander is seen in the lower-right corner, above the K-Board.

Genre Usage

Based on how artists on Equipboard use this gear, it is most commonly found in the following genres.

Used With

Based on how musicians on Equipboard use Keith McMillen Instruments MIDI Expander, it is most commonly used with the following gear.

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