Keith McMillen Instruments K-Mix

The K-Mix squeezes a mixer, an audio interface and a MIDI controller into one very tactile box.

Hardware and software developer Keith McMillen is nothing if not inventive, and has a track record of over 35 years of musical innovation. In more recent years his eponymous company, California-based Keith McMillen Instruments (KMI), have introduced the SoftStep 3D foot controller, QuNeo 3D pad controller and the QuNexus and K-Board keyboards, all of which feature interfaces based on KMI’s touch-sensitive, ‘opto-tactile’ Smart Fabric.

The latest KMI product, the K-Mix, builds on this technology to deliver not only an eight-in/10-out audio interface and DAW controller for Mac, iOS (very soon) and Windows (arriving soon, though no actual date as yet), but also an 8:2 fully programmable digital mixer, with three-band semi-parametric EQ plus dynamics on every input channel and the main output, three stereo aux sends and an on-board global reverb. As a mixer, the K-Mix can operate not only in conjunction with Mac, PC, iOS and MIDI, but also as a stand-alone audio console in a live environment.

Three Into One Does Go

Size-wise, the K-Mix is about the size of a large paperback. Its opto-tactile control surface is made up of eight channel faders; one master fader; four circular control pads; nine channel-select buttons; four buttons in a diamond-shaped block that can either set the unit’s operating modes (‘banks’ in KMI-speak) or act as MCU (Mackie Control Unit) transport controls; 16 buttons that give access to the functionality that you’d find on a similarly-specified, full-size digital console; a phantom power switch; and a preset recall button.

Audio inputs and outputs reside on the rear edge of the K-Mix. All eight analogue inputs are balanced, the first two being XLR/TRS combo connectors providing connection to KMI’s proprietary Pre microphone preamplifiers on the XLR and Hi-Z instrument/line-level sources on the jack. Individually switchable phantom power can be supplied to the XLR connectors at globally switched levels of 12V or 48V. The remaining six balanced TRS inputs can be switched to accept either line- or phono-level signals.

Eight balanced TRS jack sockets carry the K-Mix’s analogue outputs and are set up with the main output on 1+2, aux 1 on 3+4, aux 2 on 5+6 and aux 3 on 7+8. In surround mode, these can be configured in full-range 8.0, 7.1, 5.1 and 4.0 modes. When the bass management feature is activated, all eight outputs are high-passed and the low-passed subwoofer information is sent out through the front-edge mini-jack headphone output.

On the rear edge, in the space between input and output connector banks, you’ll find two USB ports. The ‘Audio’ micro USB port is used both to bus-power the K-Mix, and to connect it as an audio interface and/or DAW controller to an iOS device, Mac or PC. The ‘Control’ mini-USB port connects either to a KMI MIDI Expander (equipped with physical MIDI sockets) or to the included power supply for use either when the K-Mix is being used stand-alone or when the Mac or iOS device to which it is connected cannot provide enough bus power.The K-Mix’s rear panel is where we find the unit’s eight audio inputs and outputs, as well as two USB ports for audio and control.

Audio Interface

In addition to its analogue audio functionality, the K-Mix is a class-compliant eight-in/10-out audio interface that is capable of supporting 44.1, 48, 88.2 and 96 kHz sampling rates. USB I/O setup is carried out in the editor and allows the K-Mix’s eight inputs to be sent to the computer on an individual basis either immediately after the A-D converter (Pre) or post EQ, dynamics and aux sends but pre-fader (Post). On outputs 1+2 (the main outputs) the signal is sent from a pre-fader point that is post the main output EQ, dynamics and return for the on-board reverb, creating the possibility of having two sets of EQ and dynamics available on those outputs if required.

USB returns 1-8 from the computer come back in on an individual pre/post basis. When the headphone socket is set to act as a discrete stereo output, the final two available returns (9+10) are routed to it, allowing the user to listen to, for example, a monitor mix from a DAW.

Control Surface

When the K-Mix is connected to a computer, three virtual MIDI ports are created, two of which (Audio Control and Control Surface) allow for direct two-way communication between the K-Mix and a computer or iOS tablet and, in the case of the Expander port, between K-Mix and any connected MIDI device via the optional KMI Expander.

How the control surface and ports operate is related to the K-Mix’s operating modes or ‘banks’. The Mix bank is where all audio manipulation is carried out and, in this mode, the Audio Control and Expander ports are active. In this mode the K-Mix does not output MIDI signals, with the exception of the ‘diamond’ pad which sends MCU-compatible transport commands: start, stop, RTZ and record. Correctly configured incoming MIDI messages can control the Mix bank parameters — EQ and dynamics, aux send levels, pan, fader levels, etc — enabling the automation of the K-Mix from a DAW or a connected MIDI device.

Both the Control Surface and Expander are active in the three remaining banks: MIDI 1, 2 and 3. In a MIDI bank mode, the K-Mix’s faders and ‘rotary’ pads can send MIDI CC numbers, and the switches can transmit any Note number on any MIDI channel except Omni. Individual switches can be set to act either as momentaries or as toggles. Controller and Note numbers can be set individually for each bank, giving the possibility of three sets of completely different CC and Note setups within each preset.

The Editor

Although the K-Mix can be operated without a computer, there are certain functions that are only accessible via the free K-Mix Editor software. This editor has a neat, clutter free, multi-screen interface that, in addition to those parameters that can be controlled from the K-Mix itself, also allows access to additional functionality, both setup and operational.

A complete K-Mix parameter configuration, eg. for a particular track or song, can be saved via the Editor as a preset for instant transmission to the K-Mix. Any number of presets can be stored and a selection of up to 12 of these can be downloaded to the K-Mix for instant recall.

Channel processing in the K-Mix Editor software.

Mixing It Up

As a standalone eight-input/eight-output digital mixer, the K-Mix offers an impressive amount of on-board functionality via its physical user interface. The faders and pads, although they require a definite though light touch, are very responsive, whether you are moving your finger along the surface or simply tapping it to jump to a value.

The position of the faders, the rotary controls being emulated on the circular pads, and the status of the switches, are indicated by the LEDs that can be seen through their semi-translucent surfaces. At present, these LEDs are not particularly bright and their status can often be difficult to discern in strong light, an issue that KMI are actively addressing. To reduce friction between their surface and a user’s fingertips, the faders have a shallow, vertically-ridged scoop in their surface in which a shallow horizontal notch indicates the unity gain point. For me it was the push-buttons that took the most getting used to as, without tactile feedback, my initial tendency was to press too hard and I had to learn to ease off and to use a pressure that was only slightly greater than I’d use on a physical switch.

Navigating around the K-Mix’s surface is relatively simple, the fader and ‘rotary’ pad functionality being based on the chosen operating mode. For example, Main, Aux1, Aux2, Aux3 and input Trim are level-control modes where only the faders are active. In Verb (reverb) mode the faders control the send levels from each channel and the rotaries act on all four available reverb settings, whereas with EQ, Gate, Compressor and Pan (which are essentially sub-modes of the Main mode) the rotary pads allow you to access a core set of the full range of parameter controls that are present in the Editor, whilst the faders continue to act as channel faders. Fader and rotary resolution is more than high enough to satisfy most practical requirements. However, should you need more granular control, the Fine button gives you access to a significantly higher resolution +/- trim function with which to refine your settings.

In Use

This review was carried out with the latest (V1.1 at the time of writing) firmware and Editor software (Mac only), which operated without any crashes or throwing up any bugs during the review process. However, certain global functions listed in the manual — Input Limiter, Backlight On/Off, LED Brightness and Tone Generator — are not yet implemented.

Putting these to one side, operating the K-Mix required very little in the way of a learning curve or specialist knowledge. The opto-tactile control surface — touch it and lights come on or change colour — takes only a few minutes to become accustomed to and the white legending, tiny though it may be, is perfectly readable against its black background.

Fader and rotary pad operation, once I had the required pressures stored in my fingers, was always reliable and smooth. Holding down the Shift button and touching the top or bottom of the channel fader activates Solo and Mute respectively. Multiple channels can be selected to either status, and these are indicated on the surface by changes in fader LED illumination levels and colour changes in the backlight colour of the channel select buttons. It is possible to put channels into Solo Mute status, and this is indicated by a flashing channel select button backlight.

In VU mode, the fader LEDs show the signal level, and touching the fader switches the display, momentarily, to the fader position. Since touching a fader will snap its level to your finger position, the global Pass Thru fader function has to be activated to ensure that the level does not change until your finger passes through the current position. If you’re not one for Pass Thru mode, you can simply toggle VU mode instead.

The one aspect of K-Mix’s physical user interface that took a little getting used to for me personally was the fact that its operational logic is based on assigning a channel to a function, making it impossible to assign a function to a channel. Once I’d changed from my usual ‘channel first, function second’ approach, this ceased to be an issue.

The K-Mix Editor’s aux sends page.

Powerful and comprehensive though its physical control surface is, the K-Mix really comes to life when being operated in conjunction with its Editor software, which gives you on-screen access to all the K-Mix’s functionality. The control surface is always able to control any on-screen parameters to which it has access, whilst the Editor adds simultaneous on-screen control of all these plus additional functionality and control, the combination allowing you to work extremely efficiently.

In addition to all its DSP and control capabilities, the K-Mix also sounds good. The KMI Pre microphone preamplifiers performed extremely well with both dynamic and condenser microphones on a variety of acoustic sources, and the line inputs dealt happily with an electric piano, a guitar preamp and a drum machine. The swept centre frequencies on the treble and bass EQ, in conjunction with the fully parametric mid range, make for a very effective and musical EQ. While the compressor and gate worked effectively, I wasn’t personally all that impressed by the on-board reverb, which I felt would be fine for live use, but wouldn’t quite cut it in the studio despite the flexibility offered by its controls.

Conclusion

KMI’s K-Mix packs a surprising amount of functionality into its diminutive dimensions and, given the enhancements that are currently in the pipeline, it would seem that there’s a lot more to come. Space has restricted the level of operational detail that I’ve been able to go into in this review, so I’d recommend a close reading of the manual (available on the KMI web site) to fully appreciate the K-Mix’s capabilities.

The scope of KMI’s ambition for the K-Mix means that it is currently a work in progress, in which the essential core functionalities of a digital mixing console, audio interface and DAW controller are firmly in place alongside many of the operational enhancements that smooth and accelerate workflows, but where there is still much to come.

As it is, with the current v1.1 Editor and firmware, the K-Mix is an extremely usable, compact console that would be equally at home at the centre of a Mac-based DAW setup, as a PA mixer for a solo artist, duo or small band, or as a submixer in a keyboard or modular synth setup. In the near future, once iOS and PC compatibility is released, functionality is enhanced and mapping becomes available for the major DAW platforms, I have no doubt that the K-Mix will become a very attractive option for many musicians.

I’m not normally an early adopter, but the K-Mix’s combination of capabilities (current and planned) ticks so many boxes for me in terms of what I do and how I work that this one is staying here. If you’re in the market for a small programmable digital console, an audio interface and a DAW controller, the K-Mix offers an attractive value proposition that you should certainly consider, especially once iOS and PC compatibility comes on-line.