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Digidesign M Box

USB Recording Interface For Apple Mac By Sam Inglis
Published June 2002

The most affordable Pro Tools system ever promises trouble-free USB recording, high-quality audio hardware and the freedom to record wherever you want. Is it too good to be true?

Digidesign's TDM digital audio workstations, based around Apple Mac computers with powerful DSP cards, have become something of an industry standard in music recording. Over the years, the company have also introduced a number of more affordable spin-off systems for home-studio use, relying on the native CPU power of the host computer rather than dedicated DSPs. By far the most successful of these systems has been the Digi 001 (reviewed in SOS December 1999), which bundled a multi-channel PCI audio interface with a slightly cut-down version of the company's Pro Tools recording software.

There's no output level control on the M Box: instead, you get a Mix control, which varies the blend of playback and direct-monitored signals at the main and headphone outputs.There's no output level control on the M Box: instead, you get a Mix control, which varies the blend of playback and direct-monitored signals at the main and headphone outputs.This year sees new systems being introduced both at the top of Digidesign's product range, in the shape of the Pro Tools HD workstation reviewed last month, and at the bottom — the M Box under review here. Designed in collaboration with Focusrite, the M Box is a 24-bit USB audio recording interface providing stereo analogue and digital I/O, and comes with a specially adapted version 5.2 of the Pro Tools LE recording software. It's initially available for Mac only; Digidesign say that they are planning a PC version later in the year, but haven't set a date for its release.

A Closer Look

The M Box itself is a smart-looking blue and grey affair, with a tough moulded plastic casing measuring 15.8cm high, 18.3cm deep, and 8.9cm across at its widest point. At 670 grams in weight it's light enough to be easily portable, but not so feather-like that it falls over with the slightest movement of a mic cable. Also supplied are a 1.5m USB cable, an installer CD, a registration card and a short printed Getting Started manual; full documentation is on the CD in the shape of the ubiquitous PDF manual.

It's always pleasant to discover that your sparkly new piece of recording hardware doesn't require an external power supply, but the M Box goes even further than this: no power cable is needed at all. The unit draws all its power from the attached computer via the same USB cable used to transmit data, even though it is capable of supplying two condenser mics with 48V phantom power. This is such a good idea it makes you wonder why no-one (to my knowledge at least) has done it before.

In more detail, the M Box's socketry comprises two XLR/jack combi analogue inputs with Focusrite mic preamps and insert points on TRS jacks, plus co-axial S/PDIF digital I/O, two analogue outputs on jacks and two headphone sockets. Only one of the latter can be used at once, but it's nice to have a choice of mini or full-sized connectors. All the audio sockets are on the back panel apart from the headphone mini-jack, and the USB socket is also tucked away at the rear. It's joined by a button which switches phantom power off and on for both analogue inputs together, and an LED which indicates whether the recording source is set to analogue or S/PDIF (they can't be used at the same time).

This LED is mirrored on the front panel, where there's also a second LED to indicate successful communication with the computer over USB. For each of the two analogue inputs there's a rotary gain control and a momentary button to select mic, line or instrument sources, current status being indicated by three more LEDs. The only concession to hardware metering is a red peak LED on each channel, which lights to indicate that the signal is "just below analogue clipping levels".

The output controls are even simpler. The M Box provides zero-latency monitoring by routing signals from the analogue inputs directly to the analogue outputs (including, naturally, the headphone socket) as well as to the host computer for recording. However, there's no conventional volume control for the main stereo outputs. What you get instead is a rotary control that adjusts the mix balance between the input signal being monitored and the playback signal from Pro Tools. There's also a rotary control for the headphone output level.

The final front-panel control is a dedicated mono button, which acts only on the directly monitored input signals, not on the playback signal from Pro Tools. If the mono button is not used, the two analogue inputs are panned hard left and hard right both in the phones and on the main stereo outputs, so unless you're recording in stereo, you'd probably want to keep it switched on most of the time. It can, of course, also be used to check for phase problems when you are recording with a stereo mic setup.

The M Box's rear-panel layout is upside-down compared to its front panel, but the TRS inserts on both analogue input channels are a welcome feature.The M Box's rear-panel layout is upside-down compared to its front panel, but the TRS inserts on both analogue input channels are a welcome feature.Curiously, the layout of the back-panel socketry is upside-down with respect to the front-panel controls — for instance, the controls for input 1 are at the top of the front panel, with those for input 2 beneath them, but the socket for input 1 is at the bottom of the back panel, with input 2 above it. This takes a little getting used to, but at least it's easy to pick up the M Box and peek round the back if you get confused.


The Getting Started guide lays down quite precise instructions for installing the Pro Tools LE forM Box software, including specific settings for the likes of Disk Cache and system fonts. It also insists that you choose the base set of extensions for your version of Mac OS and restart before beginning the installation process. Despite following these instructions to the letter, I found that the installed software refused to run straight away, but the problem was easily rectified by turning on the extensions relating to my third-party USB card and restarting. Users of newer Macs with built-in USB hardware are unlikely to experience this problem.

The M Box requires Mac OS 9.1 or upwards, but can't currently be used with OS X. A minimum of 128MB RAM is specified, and both QuickTime 5 and OMS 2.3.8 are required and supplied on the CD. Digidesign also insist, sensibly enough, that the M Box has a USB port to itself, and say that it can't be run from a USB hub.

Using The System

The bundled Pro Tools LE for M Box software is a tried and tested MIDI + Audio sequencing package.The bundled Pro Tools LE for M Box software is a tried and tested MIDI + Audio sequencing package.The supplied software is basically the latest version of Digidesign's familiar Pro Tools MIDI + Audio sequencer, as found in all Digi systems from HD downwards, so I won't provide a detailed description of it here. Those wishing to know more should consult Simon Price's introduction to Pro Tools (SOS February 2001 to April 2001) and ongoing Pro Tools Notes columns. The principal new feature in version 5.2 is support for DigiStudio, which allows users to collaborate remotely on Pro Tools projects via the Internet.

As well as a selection of AudioSuite off-line processing tools, Pro Tools LE is bundled with the Digi-rack collection of RTAS real-time plug-ins, which covers most of the basics including EQ, dynamics, reverb, de-essing, gating, dithering and delays. Unlike some audio applications, Pro Tools makes it easy to key gates and dynamics from other tracks. The success of Digi 001 has meant that there's also a decent range of third-party plug-ins out there, although the RTAS format still lags behind VST in the popularity stakes.

Using Pro Tools with the M Box is straightforward enough, although I feel that Digidesign could have made better use of the unit's zero-latency monitoring facilities. To record audio from one of the M Box's inputs, you create an audio Track and choose the relevant input from a drop-down list. If you want to use the M Box's direct monitoring, however, you'll want to mute the relevant Pro Tools mixer channel, and there's no way of either doing this automatically when Record is pressed, or globally turning off software input monitoring. Instead, you have to mute the mixer channel manually when you want to record, and then unmute it when you want to hear what you've recorded. This arrangement is particularly annoying if you want to drop in on existing tracks. Other software packages allow you to monitor the recorded track up until the drop-in point, but mute the software input so you hear only the directly monitored signal. This isn't possible in Pro Tools LE: if you're dropping in on a track you'll always hear your input routed through Pro Tools, whether you're also monitoring directly or not.

The Hardware Setup dialogue allows you to change buffer sizes and sample rates, and to choose analogue or digital recording sources.The Hardware Setup dialogue allows you to change buffer sizes and sample rates, and to choose analogue or digital recording sources.Another (minor) irritation is that Pro Tools' metronome only produces a MIDI click, not an audio one, so it's necessary to set up a synth or soft synth if you want to hear it. You can't use the analogue and S/PDIF inputs simultaneously, but it's a matter of moments to switch between them in the Hardware Setup dialogue. The analogue input monitor signal is always present at the outputs unless you have the Mix control turned hard right, even when you're recording via S/PDIF. There's no zero-latency monitoring on the digital input, but users with fast computers will probably find that the latency is not disastrous in any case. Three input buffer sizes are available, and buffer size can easily changed without quitting the Pro Tools application. The default setting is 512 samples, at which latency is felt as a slight but noticeable delay on instruments played through the M Box. Reducing this to the minimum 256 samples brought latency down to an almost imperceptible level, but resulted in occasional audio glitches on my system. The default setting was usable on my machine, but produced occasional warning messages about CPU overloads, and if I left an input active for a long time, the computer would sometimes descend into a frenzy of clicking. When this happened, simply opening up the Hardware Setup dialogue restored proper working, and I had no problems with the 1024-sample buffer size.

You can record at 16-bit or 24-bit, and at either 44.1 or 48kHz. The analogue inputs provide plenty of gain for microphones and electric guitars (on the 'instrument' setting), and the quality of both the converters and the analogue circuitry seems well up to scratch. Audio played back through the main stereo outputs sounded crisp and clear, and I rarely needed to have the headphone level set beyond halfway. All the microphones I tried performed perfectly well with the M Box's phantom powering arrangement, the preamps sounded very good, and the insert points behaved as expected. If you do use the insert points, the directly monitored signal is heard with the insert processing.

Using M Box With Other Sequencers

The M Box installer CD places two drivers on your hard disk. One is the Digidesign Audio Engine used by the bundled Pro Tools software, while the other is a Sound Manager driver. This allows you to use simple applications such as SoundApp to play back audio, and to hear your system sounds through the M Box.

Other recording applications must communicate with the M Box via Digidesign's Direct I/O system, a possibility which depends on the availability of a compatible Direct I/O driver (or, in the case of Steinberg software, an ASIO-to-Direct I/O driver). At the time of writing, no sequencers other than the bundled Pro Tools LE are officially approved or supported by Digidesign for use with the M Box. However, the success of the well-established Digi 001 system led all the major sequencer manufacturers to develop Direct I/O drivers, and in some cases these appear to work with the M Box as well. Initial reports suggest that Cubase and Digital Performer users have been pretty successful in using the M Box in this way, but that Logic users will need to wait for an update from Emagic.

I downloaded the Steinberg ASIO-to-Direct I/O driver, developed for use with the Digi 001. With this installed, Cubase and the M Box worked together on my system, although you don't get the option to set an audio buffer size. Cubase's Audio System Setup dialogue reported the fixed latency as 34.8ms, which was high enough to be a problem when playing electric guitar via a digitally connected Johnson J Station. Since the zero-latency monitoring is a hardware feature of the M Box, however, you can still hear your analogue inputs with no delay.

The long-term prospects for using the M Box with software other than the bundled Pro Tools LE are good, but the bottom line is that until Digidesign complete their tests of other sequencers and declare them officially compatible, users of those sequencers can expect no guarantees. For the time being, therefore, it's probably a unit that should be bought only by those who are happy to use Pro Tools LE.

A Couple Of Gripes...

My main criticisms of the M Box's design concern its monitoring arrangements. I've already mentioned the lack of a global software monitoring disable function, which limits the usefulness of the zero-latency facility, and there's another issue which can be problematic in some monitoring situations. Since the headphone socket is the only output with a level control, the only way of changing the level of the main analogue and digital outputs is by adjusting levels or muting within the Pro Tools software. Because the headphone output simply mirrors the main stereo outputs, however, there's no way of monitoring over headphones while muting the other outputs. This is less than ideal if you want to record acoustic sources via microphones, yet listen to your playback over monitor speakers in the same room. The only way to do so is to physically mute your monitoring system itself while you're recording, then bring the volume back up on playback. If you're driving your speakers from a power amp, or if you're routing the output through a mixer or stereo recorder, this might not be too much trouble. If, however, you're connecting the M Box's outputs directly to powered monitors, it's a complete nuisance — and since portability is high on the unit's agenda, this is probably what many users will want to do.

I was also slightly disappointed to discover that like the version of Pro Tools bundled with Digi 001, Pro Tools LE for M Box is limited to 24 (mono) tracks. Modern Macs are capable of handling far greater track counts if the software supports them, and even the entry-level versions of other applications such as Cubase and Logic now offer unlimited audio tracks. Admittedly, many people will never need more than 24, but others will find it very irritating, especially those who record a lot in stereo, as each stereo track uses up two of the total 24. I can't imagine that Digidesign really need this sort of restriction to maintain the feature gap between the M Box and their much more expensive HD and TDM systems, so it seems a little arbitrary. Digidesign told me that 'improvements' are planned for Pro Tools LE soon, but wouldn't reveal what they are.

Some potential buyers might be disappointed by the M Box's lack of MIDI I/O, and this does keep it from being a complete all-in-one system. However, there are plenty of good USB MIDI interfaces around, and laptop users may find it more convenient to use a keyboard that can interface directly to the computer, such as Midiman's Oxygen8 (reviewed SOS June 2002).

USP: Phantom Power & USB

If the M Box has a USP (Unique Selling Point), then it is surely the ability to phantom power two condenser mics without itself requiring a separate mains power supply. Clever design allows it to derive the full 48V phantom supply from a computer's powered USB socket, and Digidesign say that they haven't yet come across a mic that won't work with the M Box.

Aside from sheer neatness, the obvious advantage of this arrangement is that you can use the M Box with a laptop to create a completely portable system for recording where mains power is completely unavailable. Digidesign don't give exact figures, but warn that the M Box does place a significant drain on laptop batteries when used to power condenser mics, so you should probably budget for spare batteries if this is your aim.


Digidesign say that they're selling M Boxes faster than they can make them, and it's not hard to see why. For one thing, it's the most affordable Pro Tools system yet, and opens up this industry standard to a new market. For another, it seems to represent the coming of age of USB as an audio protocol. Many people have been put off other USB devices by glitches, latency problems, poor sound quality or indifferent driver support, and the availability of an integrated, robust, good-sounding setup is very welcome. Although the M Box still doesn't convince me that USB is as suitable for audio work as other protocols such as PCI or FireWire, it's the closest thing I've seen yet to a 'professional' USB interface. PC owners and those who need to use other sequencers face a frustrating wait, but as a system, the Mac/ M Box/ Pro Tools LE combination works now and it works well.


As far as I'm aware, there are no competing products with exactly the same feature set as the M Box, though there are certainly alternatives. Perhaps the closest USB options are Edirol's UA5 (reviewed in SOS March 2002) and M‑Audio's forthcoming USB Audio Duo, both of which are much cheaper than the M Box at £249. Both ship with ASIO drivers for wider compatibility and provide stereo analogue I/O with mic preamps, 96kHz support, direct monitoring and a digital output, while the UA5 adds full digital I/O in optical and co-axial formats. However, they lack the M Box's insert points and its unique ability to provide phantom power without a mains supply; nor do you get Pro Tools LE or comparable software with them..

Laptop owners could also look to PCMCIA units such as the Echo Mona Laptop (reviewed SOS June 2002). Although this is much more expensive and doesn't ship with recording software, Mona does offer good sound quality along with more analogue I/O and additional features such as word clock and ADAT-format digital I/O. To my mind, though, the most attractive alternative is MOTU's excellent 828 FireWire interface: as well as good-sounding dual mic preamps, this provides eight-channel analogue and digital I/O and superb low-latency operation with most software packages. Like the M Box, the 828 can be used with both desktop and laptop machines. Like the Mona Laptop, however, it's almost double the price of the M Box.

As far as I'm aware, there's no other unit that can currently boast the M Box's ability to supply phantom power to condenser mics without itself requiring a mains power supply. This makes it uniquely suitable for portable and field recording rigs, and will make it an automatic choice for those needing to record in situations where mains power is not available. Even those who don't will be tempted by its combination of good sound quality, portability and convenience. USB will probably never be the standard of choice for professional audio recording, but the M Box goes a long way towards making it respectable.


  • Good performance with the bundled Pro Tools LE software.
  • Good sound quality.
  • Doesn't need a mains supply, even when delivering phantom power.
  • Insert points and zero-latency monitoring on analogue inputs.
  • Ideal for use with laptops.


  • The lack of an output level control is annoying.
  • Pro Tools LE is still limited to 24 tracks.
  • The zero-latency feature would be more useful if you could globally disable software input monitoring in Pro Tools.
  • No official support yet for audio applications other than Pro Tools.
  • USB is still USB.


The M Box is a good-sounding and, in most respects, well-thought-out recording interface. It brings Pro Tools to a new price point, and is particularly suitable for portable recording setups.


£445.33 including VAT.

Digidesign UK +44 (0)1753 655999.

test spec

  • Digidesign Pro Tools LE for M Box v5.2.
  • Beige 300MHz Apple Mac G3 with 192Mb RAM and third-party PCI USB card, running Mac OS 9.1.
  • Tested with: Steinberg Cubase VST v5.0.