Probably the biggest disadvantage of Digidesign's Pro Tools and similar computer-based digital audio workstations is that they lack the hands-on physical

Probably the biggest disadvantage of Digidesign's Pro Tools and similar computer-based digital audio workstations is that they lack the hands-on physical controls of a conventional mixing desk. Various manufacturers have attempted to address this problem by coming up with inexpensive, largely generic hardware fader packs, but these generally have serious drawbacks. To begin with, most, if not all, use standard 7-bit MIDI-controller resolution, making them unsuitable for fine adjustments. Also, they usually lack the ability to address product-specific features other than simple level changes.

At the other end of the price spectrum, Digidesign offers one option for Pro Tools users: Pro Control. It has pretty much everything you need for powerful control of a Pro Tools system, but its price tag of roughly $12,000 puts it out of most users' reach.

Mackie Designs' Human User Interface, or HUI, provides a middle ground. Similar in concept to Pro Control, it provides many of the same functions (with certain important exceptions) at approximately one-fourth the cost. A MIDI-based control surface, HUI provides simultaneous real-time control over eight channels of Pro Tools' mixer, eliminating a lot of mousing.

If you are thinking about using the HUI as a general-purpose MIDI controller, however, forget it. The HUI sends combinations of MIDI controllers designed specifically for Pro Tools, and its higher resolution will not translate into better response in a sequencer or other MIDI product that uses 7-bit messages. For practical purposes, this is strictly a Pro Tools controller.

BASIC DESIGNThe HUI has eight "channel strips," each of which has a touch-sensitive, moving fader; Auto, Solo, and Mute keys; a V-Pot (a programmable soft knob that can perform whatever function you assign it); and Rec/Ready, Insert, and Select switches (see Fig. 1). Dedicated sections of keys access various Pro Tools windows, Mac keyboard shortcuts, Pro Tools automation functions, and a set of transport controls that mimic Pro Tools' transport window. In short, pretty much all the functions you're likely to need while working in Pro Tools are covered by dedicated keys on the HUI.

Other interface features include four V-Pots for automating TDM plug-in parameters, a locate/numerics keypad for number entry, LED channel "meters" and global time-code displays, and a status/parameter LCD. A prominent Scrub/Shuttle wheel and an onboard talkback section complete the main controls.

A built-in mixer allows you to set a control-room monitor mix. To this end, the rear panel has three stereo pairs of audio monitor inputs and outputs, two mic inputs with preamps, two inserts, and stereo main ins and outs (see Fig. 2).

MIDI In, Out, and Thru are also located on the rear panel. A pair of 11/44-inch Relay outputs let you toggle electrical switches, allowing you to control solo lights, recording lights, and so on. ADB ports let you extend the distance between your computer CPU and the keyboard and mouse, but they do not offer control over the HUI. You get a switchable RS-232/422 port for connection to a DAW, and a similar 9-pin expansion jack for accommodating as-yet-unspecified external control devices.

GETTING STARTEDSetting up the HUI is impressively simple. All that's required is a computer with a correctly installed Pro Tools system (version 4.1 or higher) and a MIDI interface. I connected the HUI MIDI In and Out ports to my MIDI interface, defined the HUI in Pro Tools' Peripherals dialog box, and the HUI sprang to life, the faders moving to the positions of the first eight channels in my open Pro Tools session.

The HUI's Scribble Strips (the four-character, green LCDs above each fader) also came on, showing abbreviations of the channel names. The four-character limit on names quickly became annoying, as my tracks needed longer descriptions than "kik," "snr," or "hat." For instance, what if a track is called "filtered echo melody bits" or "Lo Chorus Harm Vox Dbl"? Shortening these to "FEMB" or "LCVD" doesn't help much, especially when you're dealing with a large session.

Assuming you are familiar with Pro Tools, getting started mixing with the HUI is mainly a matter of learning which HUI controls access the various Pro Tools functions. The rest is easy.

Since the HUI has only eight channel faders, you will need to switch banks when you have a session with more than eight channels. Using the left and right Bank Switch keys, you can scroll through banks of eight channels in your current Pro Tools session; this scrolls through the Pro Tools Mix window display at the same time. The theory is that most people won't need to manipulate more than eight faders at any given moment, so why add costly additional hardware faders when you can use the same eight and switch banks? Digidesign's Pro Control also is designed around that principle, and-although I think a minimum of 16 faders would make the HUI a lot more viable as a real mixer-it does have some validity. After all, these products are already costly, and besides, HUI isn't designed to emulate an entire mixing console.

I had no problems with the functioning of the faders. They are smooth and have capacitance-sensitive caps, a feature usually found only in high-end automation systems such as Flying Faders. You start writing channel automation by simply touching the fader cap. The fader travel length (100 mm) is comparable to that of many audio mixers, and it's adequate for use in Pro Tools.

USEFUL CONTROLSI appreciated the inclusion of a Save button, which performs the standard Mac File-menu Save command when pushed twice. It's very convenient. I also like the Shift key, which turns the main faders into effects-send controls, making it much easier to automate the sends. The Scrub/Shuttle wheel also came in handy, easily beating out the mouse in the ergonomics sweepstakes. The same goes for the Edit Mode toggle key, which switches between Pro Tools editing tools, and the Mode switch/arrow keys, which allow either scrolling around the Edit window onscreen or zooming in and out.

Among the more useful controllers are the V-Pots, assignable "soft knobs" (encoders) that emulate the action of real knobs but can perform whatever function you assign them. With the channel-strip V-Pots, these functions include panning and effects-send levels. As you would think, plug-in automation V-Pots control assignable plug-in parameters.

A nice feature of these controls (as well as of the HUI's keys) is the ability to engage a soft "clicking" sound generated by the HUI when they are adjusted, letting you know you did something. This function can be disabled, but I found that it made HUI's overall interface feel more solid.

ERGONOMICSOn a device that contains this many dedicated function keys, good layout and easy accessibility to frequently used functions are critically important. Therefore, it's hard to see why Mackie decided to place the bank-switching keys up in the middle left section of the unit, where they require a deliberate effort to get to them, instead of at the lower left or right corner, where they could be accessed by touch and without having to reach across the HUI.

Another example of problematic layout is the placement of Mute and Solo keys for each channel. Rather than residing directly above the tops of the faders, where they are found on most consoles, they are above the Scribble Strips, which is nonintuitive. A better idea might have been to place the Select keys (which are not that frequently used) below the faders, where they would also be more visible, and put Mute and Solo where most people expect them to be. Similarly, most of the automation control keys are in the upper right half of the unit, instead of down next to the faders where they'd be convenient and expected.

The audio inputs and outputs provide a convenient control-room mix with three stereo inputs, three stereo outputs, and a headphone out. Although the audio ports are of good quality, monitor mixing is not the main point of the HUI. So one would think the controls for the audio section would be placed out of the way of the main automation and control functions. Instead, the less-important controls governing the HUI's audio inputs are easily reached at the right center of the panel, while the plug-in automation V-Pots are at the extreme upper right, making them a pain to use.

SLOW HANDThe HUI relies on MIDI continuous controllers to transmit its commands to Pro Tools. But reliance on MIDI presents problems because MIDI is an almost laughably slow serial interface, fundamentally unchanged since the original version 1.0 specification.

What does this mean in real life? Basically, it means that there's going to be lag, folks, and the more automation involved, the more this will be apparent. This lag is not normally a problem for sessions with light- to medium-density automation, but if you start doing moves involving most of the HUI's faders simultaneously, you will definitely notice that the onscreen faders in the Pro Tools Mix window aren't precisely keeping pace with your HUI's fader moves.

The degree to which this is a drawback depends entirely on the type of work you do. If you are using HUI for moves involving one or two faders at a time, it's not an issue. If, however, you expect HUI to leap to attention like an SSL or Flying Faders system, you're likely to be disappointed.

The HUI's reliance on MIDI is a more obvious problem where the metering is concerned. Continuous controllers are also used for transmitting channel-level meter data back to HUI for display, and the meter response is coarse, "chunky," and at times borderline unusable. I sincerely wish another solution had been chosen for this task, since precise metering is quite important if one is to rely on the HUI and not have to look at Pro Tools' onscreen meters.

According to Mackie, when the HUI is used with more modern (faster than 1 MHz) interfaces, it can take advantage of the extra speed and handle the metering data faster. However, after initially testing the unit using an old 1 MHz Opcode Studio 3, I switched to a faster Studio 4, and in my judgment, the improvement was insignificant.

I wish Mackie had used a high-speed ethernet interface instead of, or in addition to, MIDI. Digidesign chose ethernet for Pro Control, and it is far better equipped to rapidly transfer large amounts of data. The HUI has an RS-232/422 control port, but that interface is not compatible with products most HUI users would have. In contrast, ethernet is available for (or comes as standard stock with) most Macs and PCs, and ethernet gear is easily cabled and networked.

HUI AND YOU AND IThere is no comparison between using HUI and using a mouse or even a generic fader box for doing automation in Pro Tools. Initially, I thought I'd be able to use HUI to free myself entirely from looking at the Mac screen during mixing, but perhaps that wasn't realistic. After a while, I relied on the HUI mostly for moves that would have been awkward or impossible with the mouse, and for these it was extremely useful. The unit never crashed or displayed weirdness. I can't excuse the control layout, though.

As much as I'd like to have more faders, flawless high-speed response, and real metering, this unit represents the best and most comprehensive control surface solution that's even vaguely affordable. Ultimately, if you are a Pro Tools user and are sick of struggling with the mouse when you mix, chances are excellent that the HUI will do the trick in almost any Pro Tools session.

Peter Freeman is a freelance bassist, synthesist, and composer living in New York City.