couple of years ago, Digidesign made Pro Tools affordable by introducing the Digi 001. When combined with Pro Tools LE, that relatively inexpensive I/O

couple of years ago, Digidesign made Pro Tools affordable by introducing the Digi 001. When combined with Pro Tools LE, that relatively inexpensive I/O box made it possible for just about anyone to make music the Pro Tools way, albeit without the power of the bigger TDM-based systems.

Digidesign has now extended its line of affordable front-end solutions with the debut of the Mbox (see Fig. 1). The Mbox is a 2-channel, 24-bit, USB-based digital audio interface for Pro Tools LE. When combined with a laptop such as the Apple iBook, the unit becomes an inexpensive 24-track mixing and recording system that can easily fit into a book bag.


The compact Mbox stands upright on plastic feet and is designed to be placed within easy reach of the user. All the adjustment knobs are on the front panel, and all the jacks (except one of the two headphone jacks) are in the back (see Fig. 2). The overall design is simple and straightforward with flowing, curved lines that add a bit of style. (For a look at a matching hard drive, see the sidebar “Designer Drives.”) The light plastic case, however, is not as rugged as the metal housings on some I/O boxes (such as the Sound Devices USBPre), which might be better able to withstand the rigors of portable recording.

A phantom-power indicator LED sits at the top of the front panel above controls for the pair of input channels. A Source button selects between mic, line, and instrument level inputs for each channel with corresponding LEDs showing the current selection. Gain knobs adjust the input, and a single peak LED indicator for each channel helps you set your levels.

The S/PDIF LED lights when the digital inputs are active, and a USB indicator shows when there is communication between the Mbox and your computer. A Mix knob blends the input signal with the playback signal, and the result is passed to the outputs. At the bottom of the front panel, a Headphone knob controls the level of the front (⅛-inch) and rear (¼-inch) headphone jacks, and a Mono button lets you center a mono input in the headphones, so it isn't panned hard left or right when overdubbing. (It doesn't mono the output.)

The top of the rear panel sports a 48V phantom-power button, a ¼-inch headphone jack, a USB port, and 24-bit S/PDIF coaxial I/O. The Mbox always sends its analog output signal to the digital outputs as well, which is great for monitoring with speakers while recording to a DAT machine, for example.

The ¼-inch analog outputs can handle balanced (TRS) or unbalanced (TS) plugs; the 24-bit D/A converters are clean and quiet. Two ¼-inch insert jacks are provided for adding an external processor in to your input signal chain. However, you can only use the hardware inserts on the input signals before they are converted to digital signals and recorded into Pro Tools LE. You can't use the jacks as aux sends or returns within Pro Tools, which would be much more useful (although latency could become an issue with that kind of configuration). The two Neutrik combo input jacks at the bottom of the rear panel can accept ¼-inch or XLR plugs, allowing you to connect line, mic, or instrument inputs without adapters.


The Mbox comes with Pro Tools LE 5.2 — a trimmed down version of the software used by the TDM-based systems. Pro Tools LE supports up to 128 tracks of MIDI and 24 tracks of audio with 16- or 24-bit resolution and sampling rates of 44.1 or 48 kHz. The software also supports the AudioSuite and Real Time AudioSuite (RTAS) plug-in formats.

On my midrange iBook, I was able to get 24 channels of audio running off the internal drive with a limiter plug-in strapped across the main insert of a stereo master fader and with EQ and compression plug-ins on every channel. It was a little creaky around the edges, and I couldn't add any additional buses with reverb plug-ins, but it basically worked.

Digidesign has purposely left a few features out of Pro Tools LE, such as support for SMPTE time code and Feet/Frames displays (most useful in post-production) as well as the time-saving single-keystroke macros for many common functions. Nevertheless, the most essential tools are available and easily accessible.


Though I own my own studio, I am often called to do sound-design projects at other facilities. I also do a good deal of field recording for film. As a result, I have often thought about creating a portable Pro Tools rig. Recently, a post facility called, asking me to design the sound for a game onsite. I had one week to put together a system to do the job, so I decided to take the plunge.

I purchased a new Apple 600 MHz iBook laptop and grabbed the Mbox that I had been sent for review. To the basic system I added a couple of old-school synthesizers, a FireWire drive, and a pair of Mackie HR824 monitors. I was up, running, and churning out laser blasts by the end of the day. And though the system has some quirks (more on that later), it still performs like a workhorse, allowing me to consistently produce at the same pace and quality level that I normally do on my big, expensive Pro Tools system.

I wouldn't try to mix a film with my Mbox setup, and the lack of time code in Pro Tools LE precludes the possibility of editing serious post-production projects. But for the creation of individual sound-design elements and for mixing short animated projects, it can't be beat.


I also decided to try out the Mbox in some live recording situations. I took my setup to a gig and put the iBook and the Mbox right on top of my Hohner Clavinet. I connected a pair of Neumann KM 184s in an XY configuration in front of the band and recorded into Pro Tools LE. I adjusted the input level a bit as we started playing, and away we went.

I recorded three hours of music directly onto the internal drive, with the iBook's battery powering the computer, the Mbox, and the microphones. Everything went perfectly — no crashes, no problems. The resulting recording sounded fine. I wouldn't sell off my Millennia Media or Grace Design mic preamps in favor of the Focusrite preamps in the Mbox, but admittedly, they're in a completely different league and price range. Once the gig was over, I bounced the recording to disk with a bit of compression and EQ, then burned it straight to CD using the iBook's internal CD writer.

When I was asked to record the Foley for the film Adaptation, I decided to take a chance and use the Mbox on location instead of recording the tracks in my studio. I compressed the movie to a 320×240 QuickTime file and opened the movie in Pro Tools LE along with the original production recording and several open audio tracks for takes. Next, I attached a portable LCD monitor to the external video output of an Apple Titanium PowerBook and held the display so that the Foley artist could mimic the onscreen movement while wading hip-deep in a lake. We recorded the sounds of her movement directly into Pro Tools LE; the process worked beautifully, the system was stable, and the sound quality was excellent.


Although the Mbox is great for live recording, sound design, mixing, and general audio use, I have reservations about using it as a primary unit for overdub-style multitracking. The problem is latency. As with all host-based recording systems, there is a discernable time lag between the audio coming into and the audio going out of the system. The time lag sounds like a slapback echo, and on my G3/600 MHz it felt like somewhere between 40 and 80 ms. That makes recording tracks over a rhythmic bed a dicey proposition. Your internal musical timing can get confused, making it really tough to nail a part.

The Mix knob that affects the balance between the input and the playback is meant to alleviate the problem somewhat by allowing you to focus to a greater or lesser degree on the new part or the background tracks. But mixing a blend of the incoming signal with the same signal going out in sync with the backing tracks makes everything coming in sound flammed.

Moving the Mix knob all the way to the playback position lets you hear only your audio as it is being recorded relative to the backing tracks. But then there is a disconnect between your fingers playing the instrument and the resultant sound emanating from the box. (Digidesign recommends lowering the volume on the record-enabled track in Pro Tools LE to prevent the delayed signal from coming back into the headphones.)


Though the Mbox and Pro Tools LE are designed to work together, the Mbox is capable of serving as a general-purpose audio front end for other applications. The DigiSystem extension makes the Mbox selectable as the sound-output device through the Sound Manager, making it easy to play back files from such applications as BIAS Peak or Norman Franke's SoundApp.

Getting sound into third-party applications through the Mbox is a more complicated matter: different applications require different drivers, not all of which have been thoroughly tested. If you're planning to use the Mbox with a primary application other than Pro Tools LE, be sure to check with the manufacturer to make sure that the appropriate drivers are available. (Digital Performer 3 is confirmed to be fully compatible with the Mbox through the Digidesign Direct I/O driver.) In addition, because Direct I/O only allows one client to talk to it at a time, switching back and forth between Pro Tools LE and other audio applications can be a headache if the other programs route their signal through the Mbox.


The problem with new products is that they often suffer from problems that more mature products have already worked out. The Mbox suffers from a number of hardware and software problems that range from mildly irritating to thoroughly annoying.

The first issue is that there is no master volume control for the analog outputs. There's a headphone volume knob, but it doesn't control the line outputs. As I mentioned earlier, the input/playback Mix knob blends the relative levels of the incoming signal with the internal playback signal and then routes the mix to the outputs. If there is no input signal, the knob works as a volume control because it is mixing between the playback signal and silence. But if you have any input, such as an open mic in the room, that approach doesn't work. I understand the desire to create new paradigms, but an output volume control is an essential feature for most audio devices.

Another welcome feature would have been MIDI In and Out. I assume that there would not have been enough bandwidth on the USB bus to accommodate it, but it sure would be a useful addition.

The Mbox also suffers from a series of hardware and software glitches. To start with, the box outputs noise and ticks when it's powered up but before the Digidesign extensions have loaded. That means you have to turn off your audio monitors every time you reboot. In addition, upon first powering up, the Mbox often outputs silence or distortion rather than a normal signal; the problem occurs with Pro Tools LE as well as with other audio software. My work-around is to boot up with the Mbox connected to my Mac and then disconnect and reconnect the unit before starting to work.

The Mbox is also persnickety when it comes to switching back and forth between Pro Tools LE and other audio software. Problems even occur when using a program like Peak; if I quit Peak and then launch Pro Tools LE I might on occasion only get silence instead of an audio signal. The issue involves using the Digidesign sound drivers to output non — Pro Tools audio from the Mbox. The work-around is to output all other audio through the Mac's headphone output, which involves adding a mixer to the situation, taking away from the simple, portable aspect of using the Mbox in the first place. You may often need to unplug the Mbox from the USB connection and then plug it back in to clear hardware glitches, so you'll want to keep the Mbox close at hand when you're using it.

When Digidesign learned about the problems that I was having, it promptly shipped out a new Mbox. When I installed revision 20 of the firmware, Digidesign USB driver 1.0.1, and Pro Tools LE 5.2.1, a number of other problems that I had been experiencing disappeared. The problems that I've just described, however, remained.


The age of the truly portable recording studio is upon us, and Digidesign's Mbox is helping to make it a reality. By offering two channels of high-quality, USB-powered, 24-bit analog and digital I/O, the Mbox delivers an affordable and compact front end for Pro Tools software. It is, however, a terrific idea that is marred by some hardware and software glitches and by the absence of a couple of important features.

In spite of its shortcomings, the Mbox offers a great-sounding digital recording studio that you can carry around in a briefcase. For live stereo recording, sound design, and general-purpose audio work, the Mbox has a lot to offer at a very reasonable price.

Nick Peckcreates sound for film and games and is currently working on the film Adaptation. You can e-mail him atnick@perceptivesound.com

Minimum System Requirements

Mbox (with Pro Tools LE)
Any Mac CPU with a built-in USB port; Mac OS 9.1 through 9.2.2 (9.2.2 recommended); 192 MB RAM (256 MB recommended); OMS 2.3.8 (included)


If you're the type of person who likes to match your shoes to your belt (hey, I do; I even have matching purple road cases for my keyboard rig), then you'll be happy to know that Glyph Technologies (www.glyphtech.com) has released the Companion, a high-quality FireWire hard drive for the Mbox (see Fig. A).

The Companion comes in 40, 80, and 120 GB flavors ($549, $599, and $799 respectively), allowing up to 7 hours of 24-track, 24-bit, 48 kHz recording. It features a high-quality AC- and DC-filtered power supply and an advanced cooling system that kicks up the fans when the drive gets hot. The ATA drives run at 7,200 rpm with a sustained data-transfer rate of greater than 30 MB per second. In addition, the ATA-to-FireWire bridge circuitry uses the high-bandwidth Oxford 911 chip Glyph chose in conjunction with Digidesign for use with Pro Tools systems.

The Companion's case is quite rugged (much more so than the Mbox's) to better withstand abuse by musicians. All of the drive's components have been assembled to minimize acoustic vibrations and resonance (although I didn't find the drive to be any quieter than a run-of-the-mill Maxtor FireWire unit). The Companion is heavier than you'd expect, but high-quality power supplies and fans weigh more than the normal versions.

Glyph has successfully marketed a variety of storage devices that visually coordinate with popular audio interfaces, and the Companion continues that trend. The case is designed to sit right next to the Mbox, with a similar shape and a matching powder-blue curved faceplate. Although a hard drive should be evaluated for how it performs, not by how it looks, the Companion's matching case is a nice touch.

Mbox Specifications

Analog Inputs(2) ¼"/XLR Neutrik combo connectorsAnalog Outputs(2) ¼" balanced/unbalanced TRSAnalog Inserts(2) balanced ¼" TRS, pre-A/D onlyDigital I/Ostereo 24-bit S/PDIF (RCA jacks)Headphone Outputs(1) ⅛" on front panel; (1) ¼" on rear panelResolution16- and 24-bitSample Rate44.1 and 48 kHzDynamic Range(Analog Outputs) 103 dBATotal Harmonic Distortion(Analog Outputs) 0.004%Frequency Response20 Hz-20 kHz (±0.5 dB)Dimensions3.52" (W) × 6.24" (H) × 7.20" (D)Weight1.475 lb.


USB audio interface


PROS: Small, simple, and powerful. Decent-sounding mic preamps and A/D converters. Supplies +48V phantom power from the USB port. S/PDIF in and out.

CONS: Hardware and software still glitchy. No master volume control. No MIDI I/O. Hardware inserts are prerecording only. Loud noise from outputs when powering up or rebooting computer.

Digidesign, Inc.
tel. (650) 731-6300
e-mail info@digidesign.com
Web www.digidesign.com