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Alesis ADAT Digital Recorder

Article from Music Technology, September 1992

ADAT for all seasons

You've seen the advert, you've read the brochure, you've waited an awful long time... and now, at last, the real thing is here

Eight tracks of 16-bit 48kHz digital audio on an S-VHS video cassette which costs less than £20, recordable on a 3U 19" rack-mountable unit which costs just £3499 including VAT. The kind of statistics guaranteed to set pulses racing in studios across the country. Of course many of these studios, and indeed a number of individual users, may have decided they need more than eight digital tracks with which to ply their trade. For them the good news is that multiple units can be synced together to create a composite multitrack recording system consisting of up to 128 tracks! Welcome to the world of ADAT...

Despite the novelty of recording multitrack audio onto a video cassette, the underlying emphasis in ADAT's design is on familiarity. Rather than opt for the all-in-one-digital recording system approach favoured by some manufacturers, Alesis have designed ADAT to fulfill the role of a traditional multitrack tape machine in the studio. The idea is that you can simply take your existing analogue multitrack out of your recording setup, slot in one or more ADATs in its place, and be up and running as quickly as possible thanks to a minimal learning curve.

And I have to say that Alesis have succeeded admirably in this aim. Even the concept of a front-loading video cassette should be familiar to most people, thanks to the prevalence of video recorders these days. In fact, ADAT is probably easier to use than the average VCR - at least you don't end up with Channel 4 News when you meant to record Coronation Street.

But seriously, ADAT is a cinch to use. All you have to do to be up and running is hook the eight analogue inputs and outputs on the unit's rear panel up to your mixer, switch the machine on, push in a blank S-VHS cassette (there's one supplied with the machine) into the familiar horizontal front-panel cassette slot and follow a simple procedure explained in the manual for formatting the tape with Alesis' proprietary timecode. Then you rewind the tape to the beginning, press one or more of the eight track select buttons to record-enable the track(s), press the Record and Play transport buttons, and begin recording.

Well, that's the theory; in practice, I had a little trouble getting the formatting to go beyond the initial leader/data stage which precedes the writing of timecode, but that soon righted itself - or perhaps it was me that eventually got it right.

Alesis have fitted ADAT with both balanced and unbalanced audio inputs and outputs (the former on a 56-pin ELCO connector) to cater for professional and home studios alike. A sensible move, as ADAT is good enough to be used in pro studios whilst being affordable enough to be found in the better-off home studio too. Perhaps the only distinction between pro and home studios will be how many ADATs are hooked up together.

The timecode which ADAT writes to each S-VHS tape during the formatting procedure is accurate to a single sample ie, 1/48,000th of a second - somewhat more precise than SMPTE! ADAT writes the code to a non-audio track, leaving you with a full eight tracks of audio on each machine. What's more, you don't have to bother with setting levels, or worry about crosstalk (not that crosstalk is a problem on this system anyway).

As Alesis' timecode also forms the basis of synchronisation between multiple ADATs, the units should lock together very tightly and precisely - though, only having one unit for this review, I can't vouch for the how well the syncing works (I can -Ed).

What I can vouch for is how good ADAT sounds - or should I say how well ADAT records. If you had any reservations about the recording medium, the quality of circuitry that Alesis would be providing for the price, or anything else, put them aside. This is no-compromise digital audio and it shows in terms of clarity, dynamic range, punchiness, presence and a well-balanced overall sound - and, of course, silence where silence is meant to be. Also extremely impressive are the seamless punch-ins and punch-outs, which are completely devoid of gaps or glitches, and the glitchless pitch-shifting. If you get one of these units into your system, believe me, you're going to have a hard time getting it out again.

So what exactly do you have to get to grips with in using ADAT? The left half of the unit's front panel is taken up with eight 15-segment bargraph LED meters and associated record and input status LEDs, eight track select/record enable buttons, and the power on/off button. To enable one or more tracks for recording, you just press their track select buttons; they will then accept signals from the relevant inputs on the rear panel.

If you only have jacks plugged into inputs one and two, signals appearing at these inputs are routed to the remaining inputs as well - one goes to three, five and seven, two to four, six and eight - so you can record consecutively on all eight tracks from just two inputs if you want. Plugging a jack into any one of inputs 2-8 automatically overrides this assignment in favour of its own input.

The right half of ADAT's front panel contains the cassette slot, a four-digit real-time tape counter LED showing minutes and seconds, the tape transport controls, and buttons governing input/tape monitoring, tape formatting, pitch shifting, digital input selection, tape autolocation and looping. Virtually all functions are activated from dedicated buttons. Pressing the All Input Monitor button so that its built-in LED lights causes all tracks to monitor their input signals regardless of their record enable status - a useful way of quickly checking all inputs. If you're not hearing anything off tape when you should be, it's probably because this function is enabled.

The normal status for recording is to have the Auto Input function set to off: all record-enabled tracks monitor the input signal, while all other tracks monitor the taped signal. If you need to do punch-ins, you'll want to have Auto Input on, as ADAT will then monitor the taped signal for a record-enabled track up until you enter Record mode, at which point it will switch to the input signal. When you drop out of record, it will revert to the taped signal.

ADAT also allows you to set three auto-locate points. Locate 0 is effectively a return-to-zero function in its default setting, in that it indicates absolute time 00:00; however, you can also Set Locate 0 to any location on the tape - if, for instance the song you're working on begins at a point several minutes into the tape. Locate 1 and Locate 2 reference absolute times always, and are best used to 'pick out' a section of a song on which you want to work.

Enabling ADAT's Auto 2>1 function (again available from a dedicated button) causes ADAT to automatically return to the Locate 1 point after it has reached the Locate 2 point. If the Auto Play function is also enabled, ADAT will automatically enter Play mode whenever any auto-location procedure is completed. Locate points are defined on the fly by pressing and holding the Set Locate button and then pressing the required Locate button at the appropriate time during Play. You can use Locate 1 to define a start point for recording and Locate 2 to define a punch-out point. If Auto Play is enabled, ADAT will rewind to the Locate 1 point from Locate 2 and play back through the section you've just recorded.

In addition to the balanced and unbalanced audio connections mentioned earlier, ADAT's rear panel provides optical I/O connections for digital transfer of all eight audio tracks using Alesis' ADAT Proprietary Multichannel Optical Digital Interface protocol. There is also a socket for connecting, up an RMB 32-channel Remote Meter Bridge (due towards the end of the year), two 9-pin D connector sockets for sync I/O using Alesis' ADAT Proprietary Synchronisation Interface protocol, and a jack socket for footswitch-activated punching in and out.

A further jack input is provided for connection of the LRC Remote Control unit which comes supplied with each ADAT, and lastly there's a mains input socket. The compact LRC unit (which comes with an eight foot cable attached), simply provides remote control of ADAT's tape transport controls together with its monitor select and tape autolocate functions.

"This is no-compromise digital audio and it shows in terms of clarity, dynamic range, punchiness, presence and a well-balanced overall sound"

Alesis haven't stopped development of the ADAT system. Planned for release towards the end of the year are three units which will expand the functionality of ADAT in various ways and degrees. The aforementioned RMB Remote Meter Bridge will provide 32 channels of remote LED monitoring for a multiple ADAT system, while the AI-1 ADAT To AES/EBU And S/PDIF Digital Interface will allow two channels of digital audio data to be transferred in the digital domain (so no degradation of audio quality) between ADAT and a range of digital audio products including CD players, DAT machines, digital samplers and disk-based digital audio recording systems. The AI-1 will also provide sample rate conversion, allowing ADAT to record digitally from, say, 44.1kHz sources such as CDs.

But it's perhaps the BRC Master Remote Control unit that will most enhance the flexibility of ADAT. This will allow you to bounce tracks back and forth between multiple ADAT units, and also, if you have two or more ADATs, to perform cut-and-paste editing and assembly of tracks - a feature more usually associated with disk-based digital audio systems. Again, this is done in the digital domain for perfect reproduction, using the optical connections mentioned earlier.

Digital connections can be made to the BRC, the AI-1 or, of course, another ADAT. In fact, with two ADAT units hooked up digitally you can make perfect copies of your tapes in real time, whether for backup purposes or to send to a musical collaborator. The S-120 S-VHS tapes which ADAT uses provide 40 minutes of recording time.

Apparently, the BRC will also take advantage of the precision location provided by Alesis' proprietary timecode to allow you to cut and paste, autolocate and punch in and out to individual sample resolution - providing as fine a degree of control as you'll get from a disk-based system.

ADAT will no doubt find itself co-existing with a MIDI sequencer in a lot of studios, so what are the options for synchronisation with MIDI? Well, the simplest and the cheapest option if you're already using a SMPTE/MIDI synchroniser is to stripe an audio track with SMPTE code - just as you would on an analogue multitrack. You can do this while the S-VHS tape is being formatted with Alesis' own code, as ADAT allows you to record audio during the formatting process.

Alternatively, you could invest in a forthcoming inexpensive unit called Datasync being produced by JL Cooper, which will read the sync data from ADAT's rear-panel sync output socket and convert it to MIDI Time Code data, thus bypassing the need for a SMPTE code track. Apparently, Datasync will also be able to generate MIDI Machine Control deferred play, pause, record, rewind, fast forward and search commands. The BRC remote unit will remove the need for SMPTE to be striped on tape, as its features will include the ability to generate SMPTE, MTC and standard MIDI clock sync - referenced, presumably, to internally-generated Alesis sync code.

If you have an AI-1 and either a BRC or a Datasync, you'll be able to transfer two tracks of digital audio between disk-based recording systems like Sound Tools and Pro Tools and an ADAT unit and have them synced up at the same time. If Alesis succeed in getting their multitrack audio transfer protocol accepted and implemented by manufacturers of multitrack disk-based recording systems, a whole new era of harmonious coexistence between tape-based and disk-based digital recording systems could begin. Apparently the company are already in discussion with various manufacturers wth a view to getting their protocol accepted more widely. Another possibility under discussion, it seems, is remote control of ADAT functions implemented on mixing consoles. And while we're looking ahead, a computer-based graphic front end for the BRC is a possibility at some stage - though considering the BRC has yet to reach the market, let's not get too far ahead of ourselves.

ADAT has the potential to be widely accepted by recording musicians, and to exist in a symbiotic relationship with disk-based systems for some time to come. When you consider that one inexpensive and readily-transportable 40-minute S-VHS tape can store up to 1.8Gb of digital audio data in playable form, and compare that to disk-based storage media, it's apparent that digital tape has a lot going for it.

At the same time, the operational simplicity and functional familiarity of ADAT, not to mention its affordability and, of course, its recording quality, should ensure that plenty of studios and musicians who wouldn't consider disk-based systems will be only too happy to go for digital tape.

However, Alesis may not have it all their own way. Tascam will apparently be launching a comparable system in the Autumn, though how it will compare unit-on-unit and whether it will be able to compete with the larger 'ADAT system' remains to be seen. No doubt other manufacturers are beavering away on their own systems, because the market is potentially huge as musicians begin to cross over from analogue to digital multitrack tape recording. Will Alesis steal a march on their competitors, or are they destined to be forgotten pioneers? Only time will tell, but I'd say they're in with a strong chance of making ADAT the standard against which other systems are measured.

Transport & Audio Systems

  • Recording format: ADAT (Alesis Digital Audio Tape) rotary-head digital recording using S-VHS tape
  • Recording time: 40 minutes typical per S-120 cassette
  • Fast Forward/Rewind Rate: Approx. 20 x play speed unwrapped. 10 x play speed wrapped.
  • Fast Audio Scan Rate: Approx. 3 x play speed.
  • Number of Audio Channels: Eight
  • A/D Conversion: 16-bit linear audio. Delta-Sigma 64 x oversampling, single converter per channel
  • D/A Conversion: 18-bit linear, single converter per channel
  • Sample Rate: 48kHz nominal: user-variable from 40.4 - 50.8 kHz (-3... +1 semitone)
  • Frequency Response: 20Hz - 20kHz, +/-0.5dB
  • Dynamic Range: Greater than 92dB from 20Hz -20kHz, A: weighted
  • Distortion: 0.009 Total Harmonic Distortion + Noise at 1kHz, 0.5dB below maximum output, A weighted
  • Channel Crosstalk: Better than -90dB at 1kHz
  • Wow and Flutter: Unmeasurable

Inputs, Outputs & Sync


  • Balanced: Single 56-pin ELCO connector block
  • Unbalanced: Sixteen quarter-inch jacks (eight input, eight output)


  • Connectors: Two EIAJ fibre-optic jacks (one input, one output)
  • Communications Protocol: ADAT Proprietary Multichannel Optical Digital Interface


  • Connectors: Two 9-pin D-Sub connectors (sync in and sync out)
  • Capability: Automatic master/slave syncing of up to 16 ADATs (128 audio tracks), with single-sample accuracy, using ADAT Proprietary Synchronisation Interface

  • ADAT Digital Audio Recorder £3499
  • BRC Master Remote Control £2000-2500 (TBA)
  • RMB Remote Meter Bridge £TBA
  • AI-1 ADAT to AES/EBU and S/PDIF Interface c.£1000 (TBA)
  • ADAT S-VHS Mastering Audio Cassette £17.99
  • JL Cooper Datasync c.£300 (TBA)
  • Pro-Co ADAT balanced (+4dBu) I/O cables, 56-pin Elco connector to either 16 XLR or 16 quarter-inch jack plugs: 5' £243.40, 10' £260.17, 15' £276.96, 20' £293.75 Pro-Co ADAT unbalanced (-10dBV) I/O cables, quarter-inch jack plugs to either 16 RCA phono or 16 quarter-inch jack plugs: 5' £82.24, 10' £90.64, 15' £99.03, 20' £107.43.
  • All prices include VAT.

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Getting It Off Pat

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MIDI By Example

Publisher: Music Technology - Music Maker Publications (UK), Future Publishing.

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Music Technology - Sep 1992

Gear in this article:

Digital Tape Deck (Multitrack) > Alesis > ADAT

Review by Simon Trask

Previous article in this issue:

> Getting It Off Pat

Next article in this issue:

> MIDI By Example

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