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Mackie HUI

Control Surface For DAWs By Mike Collins
Published December 1998

HUI in operation with Digidesign's Pro Tools 24.HUI in operation with Digidesign's Pro Tools 24.

Users of computer‑based recording systems often feel restricted by the limited degree of physical control available when it comes to mixing, especially when compared to a traditional setup centred around a hardware mixer. Mike Collins tries out a new system from Mackie which aims to improve matters.

Mackie's new Human User Interface, first previewed in SOS January '98, was designed to offer a hardware interface for software‑driven digital audio workstations. Digidesign's Pro Tools 4.1 software is the first to support the device, although Mackie intend that other DAWs will eventually also be able to work with the HUI. So what is HUI for? Well, as most SOS readers will know, Pro Tools' onscreen mixer is normally controlled using your computer's mouse. The problem, however, is that a mouse is far from being the ideal device for controlling a mixing console — it is difficult to drag the faders smoothly, and 'turning' knobs on screen can be awkward, to say the least. Consequently, several hardware controllers have been developed as an alternative to software front‑ends over the years, including models from Penny & Giles and JL Cooper: all of these, however, offer only a limited number of controls compared with the HUI, which seeks to give the operator hands‑on control of virtually all of Pro Tools' mixing and editing parameters, as well as a full set of transport and locator controls.

At first glance, the control surface looks rather like a compact digital mixer, with eight assignable faders, associated Select switches, and an electronic 'scribble strip' which picks up the channel names from your Pro Tools project and displays these handily above the faders. This feature alone won my instant approval! The faders are motorised so they move to reflect automatically the positions of Pro Tools' onscreen faders. The HUI also has a built‑in meter bridge with eight pairs of dual LED 'ladders'. With mono Pro Tools tracks, only the left LED 'ladder' lights up, while both are used with stereo channels. Having these meters just where you need them is great, especially if you are using the ADAT Bridge interface, for instance, which, unlike Digidesign's 888 I/O hardware, doesn't have any meters.

For the project studio operator, however, the biggest deal with the HUI may well be that it gives you many of the extra facilities you need to run your Pro Tools system without using an external mixer. With a conventional Pro Tools setup, despite the host of mixing facilities on hand, an external mixer is normally still required in order to provide microphone inputs (the Digidesign I/O interfaces only operate at line level), and to control monitor feeds and headphone foldback mixes for musicians performing overdubs. Additionally, an external mixer will usually be the only means of creating a talkback facility for the engineer/producer to communicate with the musicians in the studio area. The HUI, however, effectively caters for all these basic requirements within its control room section which offers three stereo inputs and three stereo outputs, plus a headphone output, as well as two high‑quality microphone preamplifiers which can provide line‑level feeds into the analogue inputs on an 888 or 882 I/O interface. These mic preamps are similar to those found on Mackie's professional analogue mixers and have plenty of gain, insert patching and phantom power for condenser mics. A third mic preamplifier is available which is intended for use with a remote talkback mic.

The three stereo inputs can be used in a variety of ways — for example, you might just have one stereo pair of outputs from Pro Tools and use the other two pairs to connect a CD player and a cassette or DAT recorder.

Connecting the control side of HUI to the Pro Tools system requires only a couple of MIDI cables running to and from your MIDI interface. If you are using OMS, your system configuration also needs to include the device settings for the HUI. The Pro Tools software has a HUI 'personality' file which can be selected in the Peripherals dialogue — as soon as HUI is selected as a peripheral, the Pro Tools software will start communicating with HUI, which will immediately display timecode if everything is hooked up correctly.

Getting Into The Details

Mackie HUI

Each channel strip has a 100mm, touch‑sensitive motorised fader which can be assigned to control channel level, aux return level, MIDI track level or master fader level. Above each fader is a channel select switch to use when assigning groups and so forth, and a 4‑character LED display where you can display the channel's name, group status, input and output source, send and insert status, or pre/post status for sends. Three buttons above this are provided for muting, soloing and enabling automation, below a Pan/Send 'V‑Pot' and an associated selection switch which can also be used to choose items from scrollable I/O assignment lists or to choose send destinations. 'V‑Pot' is Mackie's jargon for 'virtual potentiometer' — a name chosen to reflect the fact that these pots can perform different functions depending on the software being used with the HUI, a sensible idea given that Mackie's intention is that the HUI will control other software packages in the future.

To the left of the channel strips are several groupings of buttons. From the bottom up, the first group of eight buttons lets you control a number of frequently used keyboard commands, such as Command, Shift, Undo and Save. Above this, six buttons are provided to let you select the various windows in Pro Tools — Edit, Mix, Transport and so forth. Next up is a pair of channel switches and a pair of bank select switches, which you can use to bring single faders or banks of eight faders (if you are using more than eight channels in Pro Tools) up on the channel strips. The top group of control switches includes the input/output assign switches, a Suspend switch which lets you temporarily disable the automation globally (a neat idea), a Default switch which lets you set selected channels back to their original settings (another neat idea!), and the Select/Assign switches which you use to choose what a track's V‑Pot will control. The default setting is Pan, but you can also assign the V‑Pots to control any of up to five auxiliary sends, Mute or Shift. The last couple of switches at the top are for Record/Ready toggling (ie. to enable or disable all the tracks for recording) and for Bypass (which lets you bypass any channel inserts, whether hardware or DSP plug‑ins, on any selected channels).

To the right of the channel strips are five main groupings of controls — the DSP Edit/Assign section, the Switch Matrix section, the Control Room section, the Talkback section and the Transport section. The DSP Edit/Assign block is at the top right, and sits beneath a 40‑character, two‑line fluorescent display which shows up to four plug‑ins or up to eight plug‑in parameters, and is also used to display general HUI text information. The DSP Edit/Assign controls include an Assign switch which allocates plug‑ins to channel strips, a Compare button which lets you compare the current DSP parameter setting with the previous one, and a Bypass switch to disable the plug‑in parameters or any plug‑in assigned to the channel, as applicable. The Insert/Parameter switch lets you toggle the display between the plug‑in assigned to a particular insert and the plug‑in parameters for editing. A rotary Scroll control is used in conjunction with this, either to toggle the display between Inserts 1‑4 and Insert 5, or to scroll through control parameter pages for the currently active plug‑in. There are also four assignable rotary controls with associated Select switches, which you use to assign plug‑ins and edit plug‑in parameters corresponding to the HUI display and Pro Tools software screen displays.

Whether you use it on its own or with another mixer, the HUI hardware controller undoubtedly makes a superb partner for the Pro Tools system.

The Switch Matrix section contains controls for global information enabling, mode selection, group creation and so forth. There are eight Function (F) keys which let you access special HUI features. F1 clears clip and peak holds from the meter; F2 activates Relay Outputs 1 and 2 which let you remotely control Play and Record functions on other equipment using HUI's Play and Record buttons; F3 lets you disable the audible click function for the V‑Pots below the fluorescent display; F4 displays the version number of the HUI 'personality' file currently installed in the host computer; F5, 6 and 7 are reserved for future expansion, and F8 acts as an escape switch to cancel any assignment mode or onscreen dialogue. Underneath the F‑keys are four groups of switches. The first group, labelled Auto Enable, includes fader, mute, pan, send, plug‑in and send mute switches to let you globally enable these functions. The next group of switches, labelled Auto Mode, lets you enable, disable, record or edit automation on individual channels or channel groups. Options include Read, Touch, Latch, Write, Trim and Off. Next are the Status/Group switches which are used to query automation, monitor and group status, and to create or change groups. The last group of controls lets you perform standard editing functions including Capture, Separate, Cut, Copy, Paste and Delete. Below these is a display which shows the current time location in timecode, feet or beats, or simply in minutes and seconds, and to the right of this you will find a numeric keypad which can be used to control the locate feature.

Underneath the timecode display, the Control Room section lets you control your input and output sources and the Master Volume. The input source switches choose between monitor inputs 1, 2 and 3, and a Mono button is also provided to sum all the signals via the Master Volume control. There are individual output level controls for the three stereo output pairs, along with switches to mute them individually or simultaneously, and a Dim switch is provided which lowers the monitor output level by a set amount, the default being 20dB. Below these controls is a talkback enable switch and an associated talkback level control, along with the built‑in talkback mic.

Finally, the Transport controls are situated at the lower right of the control surface. Large buttons let you control Pro Tools' Rewind, Fast Forward, Stop, Play and Record functions, and switches are provided to let you set the In and Out points for punch‑ins, audition the section you've selected, and set the Pre‑ and Post‑roll amounts before and after the punch‑in. Another row of switches is provided to let you Return to zero, go to the End, put Pro Tools Online, engage Loop playback, or enable the Quickpunch feature. A further set of four switches is available to let you navigate, zoom, and make selections in the waveform display — an associated mode switch lets you choose whether these switches will act as horizontal/vertical view expanders/contractors or whether they can be used to locate the cursor, as an alternative to using the tab and arrow keys on your computer keyboard. There is also a large jog wheel with a pair of associated buttons to switch this between Scrub and Shuttle modes.

Rear Panel

Mackie HUI

On the back panel is a standard IEC connector next to a power on/off switch. To the right of these is a pair of MIDI sockets and two pairs of Apple Desktop bus connectors, to let you feed your computer's mouse and keyboard connectors via the HUI. A couple of 9‑pin connectors are provided to allow connection to other external devices, one of which is switchable between RS232 and RS422 operation. A pair of quarter‑inch jack sockets is provided for footswitches to control functions such as play or record. Six quarter‑inch jacks feed balanced or unbalanced line‑level signals into the monitor section, and another six quarter‑inch jacks provide balanced or unbalanced line‑level outputs for monitoring or other purposes. Beneath these is a single stereo headphone output jack.

At the far right of the rear panel are three microphone input channels, all with XLR sockets, +48V phantom powering and trim controls to cater for a wide (60dB) range of input signals. The first of these is intended for use with an external talkback microphone, and a 'trigger' jack input/output is also provided for activating the HUI's talkback function remotely from another console, or using a footswitch. The other two input channels are intended for microphones or instruments that you wish to record into Pro Tools. Both of these have quarter‑inch TRS insert points so you can connect signal processors such as compressors across the channels. Each of these two mic channels also has a quarter‑inch jack socket which will normally be used to let you feed unbalanced or balanced signals to a Pro Tools interface. The microphone preamplifiers are definitely up to Mackie's usual high standard, and provide an excellent way of connecting low‑level signals to a Pro Tools 888 interface.


The HUI's monitoring facilities are particularly flexible, supporting up to six discrete channels of surround sound — in stereo monitor mode, with the Discrete switch turned off, any of the three stereo input sources can feed any of the three stereo output pairs, and all the outputs can be active at once, so you could send outputs to various combinations of monitor speakers or to external recorders such as cassette machines. Keep in mind, however, that these outputs are designed for monitoring purposes only — not for mixing. When the Discrete switch is engaged, the control room section becomes a discrete surround matrix capable of either standard 4.1 (L/C/R/S plus subwoofer) or 5.1 (L/LS/C/R/RS plus subwoofer) surround operation. With this setup, you can connect up to three pairs of stereo 'stem' outputs from the Pro Tools audio interface to the HUI's monitor inputs and feed these to the three output pairs, whereupon the level controls for the three HUI outputs can be used to trim the output levels of the respective mix stems. These surround monitoring features make the HUI particularly suited to post‑production work for video or DVD which increasingly use surround formats.

The Bottom Line

There is no comparison between using a mouse to control Pro Tools and using the HUI; with the latter, everything simply works so much more efficiently. The jog wheel is much smoother in action, the faders feel much better, and if you want to hit a Solo or Mute you just have to reach out and touch the button! Also, being able to see plug‑ins' parameters displayed numerically and control them using the V‑Pots lets you run your session much more effectively than when you have to mouse around the graphical plug‑in displays on the Mac screen.

Whether or not I would be prepared to recommend using a 'HUI Pro Tools' without an external mixer of any kind would largely depend on what kind of work it was expected to do. With the latest Pro Tools MixPlus system, which has much more DSP available for plug‑ins, or with an expanded Pro Tools system with plenty of extra DSP Farms, you can now have enough signal processing available to make very sophisticated and ambitious mixes with Pro Tools alone. And if you only need to record or overdub instruments in mono or stereo, then the pair of mic preamps in the HUI should be fine.

My own setup, however, consists of a standard Pro Tools 24 system with just one DSP Farm, and will only let me use one plug‑in, or just a few EQs or compressors, when I have 32 tracks of audio in a mix session — nowhere near enough signal processing for a decent mix. Consequently, I normally use my Pro Tools alongside a Yamaha 02R mixer, with 16 separate outputs connected to the 02R's 16 'tape' returns. This allows me to EQ, compress or add reverb or delay effects from the 02R without needing to use plug‑ins. I also do some recording and overdubbing, and can occasionally need to record up to four or more instruments at once. However, if my work was mostly post‑production and editing, with only occasional overdubs using just one or two mics, then I think the HUI certainly could be said to offer a viable alternative to using an additional external mixer, provided that you have sufficient DSP in the system to cater for all your mixing requirements. But whether you use it on its own or with another mixer, the HUI hardware controller undoubtedly makes a superb partner for the Pro Tools system, making the system significantly easier to operate for both the project music studio and the smaller post‑production studio working with surround sound.

Demo Mode

Like most hi‑tech studio equipment, the HUI has a self‑demo mode which runs through the features while displaying explanatory comments. The meters light up in bright red, green and yellow; the faders whizz around; then the buttons light up while their functions are described in the display. Finally, at the end of the demo, the display cheekily announces "I need a nice home with someone like you. Won't you buy me please!"


  • Makes Pro Tools much easier to use, giving you real hardware controls and faders.
  • Could mean you don't need another mixer.
  • Flexible monitoring options.


  • You'll still need lots of DSP to perform complex mixes in Pro Tools.


The HUI really unlocks the power of Pro Tools' integrated mixing capabilities, but costs as much as some fully‑featured digital mixers.