Alesis M20 Digital Recorder

Its sophisticated full-servo direct-drive transport, and true 20-bit capability brings modular digital multitrack recording up to a world-class level, with finely detailed audio that unquestionably surpasses even the best analogue mastering recorders. The Alesis M20 was engineered for demanding, around-the-clock applications which require the highest standard of audio quality as well as low maintenance, quick response and built-in SMPTE/ EBU time code synchronisation. Using the same S-VHS tape and sample-accurate multi-unit synchronisation that made the Alesis ADAT® the most popular digital multitrack ever made, the M20 will revolutionise professional recording and post-production studios in the same way the original ADAT revolutionised the project studio world.

True 20-bit uncompressed linear encoding: the ADAT Type II format
The Alesis M20 features the new ADAT Type II format, which records eight tracks of true, linear 20-bit digital audio onto tape, without using external converters or multiplexers. No other modular digital multitrack recorder offers this level of audio quality. 20-bit recording offers much greater sonic detail than 16-bit recording since each additional bit doubles the number of values that may be recorded, resulting in an increased dynamic range of up to 6dB. To capture this incredible fidelity, the Alesis M20 employs built-in, high-resolution, oversampling A/D and D/A converters.

The Alesis M20’s ADAT Type II format meets or exceeds the specifications of almost everything else in a professional studio (and goes considerably beyond the specifications of Compact Disc). ADAT Type II recording greatly reduces quantisation distortion, for a pristine, uncoloured, undistorted sound that’s natural sounding even at low recording levels. Unlike some hard disk recorders, the M20 uses a linear recording format, meaning that no data compression of any kind is applied to the signal going to or from tape. Plus, a 60-minute tape recorded in the ADAT Type II format holds over 3 gigabytes of audio data, with no upload or download time required…just pop in a new set of tapes and start recording.

Inside the Format, Part II: The compatibility factor
Part of the advantage for professional studios to employ a M20 recorder is its compatibility with the original Alesis ADAT, the ADAT-XT and other ADAT Type I-format 16-bit recorders. Since the M20 will automatically detect whether an S-VHS tape has been formatted in the ADAT Type II 20-bit format or the original ADAT Type I 16-bit format, commercial studios can provide their high-end services to tracks created at ADAT-based project studios. When it’s time to start a new project, you simply select whether you want the tape to be formatted in 16-bit or 20-bit mode.

The ADAT Optical ports and ADAT Sync jacks on the back of the M20 use the exact same format as all previous ADAT models use, even when in Type II mode, so M20s may be combined in a system with all existing ADAT-format recorders. The M20 will send out 20 bits per track on its ADAT Optical output, and is capable of dithering its 20 bits to 16 bits on the ADAT Optical port for higher fidelity when received by Type I machines. M20s, ADATs, and ADAT-XTs all may be linked together into a single system using the same 9-pin DSUB ADAT Sync input and output cables ADATs have always used. You can record on the M20 in Type II mode at the same time other ADATs in the system are recording in Type I mode. Note, however, that Type II tapes can’t be played back in Type I-only machines.

Built-in SMPTE/EBU time code synchronisation
The Alesis M20 is designed for use in professional time code applications. Time code, MIDI, word clock, and video reference in and out jacks are all built into the back panel, so you don’t need to purchase any optional cards or external boxes for a complete chase-lock system. For location recording and post-production applications, a new read/write SMPTE/EBU time code track allows discontinuous time code to be printed onto a special subcode area of the tape without using up a track, so different sections of tape can be uniquely identified without having to manually change offsets from the built-in sample accurate ABS time code of the ADAT format. The Alesis M20 has a built-in SMPTE/EBU time code reader/generator that can operate at any time code frame rate (30 FPS and 29.97 FPS drop or non-drop, 25 FPS, and 24 FPS) and can synchronise at any of the industry-standard sample rates (48 or 44.1kHz, plus pull-up and pull-down rates).

With this internal chase-lock synchroniser, you need only a set of XLR cables to synchronise the Alesis M20 to time code. You can use the M20’s MIDI IN jack to receive MIDI Machine Control (MMC) commands from a sequencer or other controller without external converter boxes. The M20 can even read and write 100 namable location points to the data section at the head of the tape. Also, any slave ADATs or ADAT-XTs you connect to the M20’s SYNC OUT jack will follow the M20 wherever time code or MMC commands tell it to go: no BRC or AI-2 is needed.

Total control from the front panel
The M20 supports all of the features engineers have come to expect from the ADAT, ADAT-XT, and BRC Master Remote Control. Individual M20s in a system may be offset from each other by any amount with single sample accuracy using the onboard 10-key pad, or by various methods of capturing an existing offset, allowing digital copy-and-paste editing from tape to tape.

Individual tracks may be delayed up to 170 milliseconds at 48kHz (or 185ms at the 44.1kHz sampling rate). Auto Punch-In and Out with Pre-Roll and Post-Roll are supported, as is Rehearse mode. Auto Play and Auto Return are used in conjunction with any of the 100 locate points in the Alesis M20’s memory, and all of the locate points can be given an 8-character alphanumeric title and stored to the data header at the front of the tape. Onboard digital routing allows you to copy from track to track within the same machine, or between any tracks of other ADATs in a system. The M20 also offers front-panel control for pitch adjustment from 39.289kHz (-200 cents at 44.1kHz) to 50.854kHz (+100 cents at 48kHz).

Unprecedented flexibility and first-time features
The M20 also has features never before offered on an ADAT-format recorder. These include individual input select switches on each track, so you can monitor source or tape through the machine’s electronics at any time without disturbing other tracks. You can even record from a digital input on one track at the same time you record from an analog input on another track. The back panel of the M20 features both XLR inputs and outputs and an ELCO-type multipin connector, both at the professional +4 dBu level, for easy connection to any system.

For professionals who want to set their own nominal input/output level reference, there are internal input/output trimpots allowing you to calibrate the M20 to anywhere from -20 dBFS to -10 dBFS for a +4 dBu input. A special fine display metering mode for the front-panel display allows you to set levels with 0.2 dB accuracy. The Alesis M20’s larger physical design (4 standard rack spaces) allowed Alesis engineers to add a secondary vacuum fluorescent display that displays metering and tape status data separately from tape counter, time code and synchronisation information. An optional accessory for the M20 is a rolling rack slider assembly for quick, easy access from broadcast-type rack systems.

Since 1991, the name Alesis has become synonymous with digital multitrack recording. With almost 100,000 units in use worldwide, the award-winning Alesis ADAT® 8 Track Digital Audio Recorder has become the most popular digital recorder ever made. In fact, the immense popularity of ADAT has been responsible for the formation of a whole new recording environment…the professional project studio.

The ADAT Type I format, used in the original ADAT as well as the ADAT-XT, records eight tracks of 16-bit linear digital audio onto standard S-VHS cassettes. This inexpensive, readily-available recording medium allows recording times of over an hour. It employs a modular design that allows you to use it as a stand-alone 8-track device, or to link units to form a digital recording system from 16 to 128 tracks, allowing project studios to expand their capabilities in increments that meet their needs and their budget.

With the introduction of the M20, professional studios can use the advantages of the new ADAT Type II format to their benefit. The ADAT Type II format keeps all of the great features that made the original ADAT format perfect for project studio recording…S-VHS tape media, modular design, and sample-accurate synchronisation. The world of twenty-bit recording – with up to 115 dB of dynamic range possible with the M20’s built-in A/D converters – no longer requires a jumble of outboard converters or confusing multiplexers.

Yet, backwards compatibility with the huge base of existing ADAT 16-bit recorders is maintained, with the added benefits of built-in time code, jog/shuttle capability, analog Aux track, 100 onboard locates, and a slew of other features that professionals will appreciate. For pro studios looking to update their main recording device, three M20s constitute a 24-track, 20-bit digital recording system with built-in time code synchronisation, all for less than the price of a 2″ 24-track analog deck, with over 30dB more dynamic range and dramatically lower tape costs. There’s no longer a reason for any facility to stay on the sidelines of the modular digital multitrack revolution.

An all-new direct drive transport design
The transport used in the M20 is un-surpassed for the ultimate in tape speed and handling. Manufactured for Alesis by Matsushita, the “IQ” transport has seen millions of hours of hard industrial service in top-of-the-line professional VTRs and duplication systems. Adapted by Alesis engineers for use with the ADAT format, the transport features:

• Direct-drive capstan (for faster sync from stop and greater control in jog/shuttle mode)
• Direct-drive full-servo reel motors (no idler wheel to clean or replace, and no brake adjustments required)
• Tension sensor arms (so the deck’s internal control software can constantly monitor and adjust tape tension)
• Twin tachometer output (so software can more precisely monitor the reel motor status)
• Automatic head cleaning wand (reducing the need for maintenance)

The improvement in transport speed, feel and control for professional audio recording facilities is quite dramatic. For post-production applications, the M20’s world-class transport can be trusted for your most crucial projects.

The Jog/Shuttle wheel and the Aux track
Because of the editing-quality transport, Alesis engineers were able to incorporate a true jog/shuttle wheel into the transport design for the M20. Similar to those found on high-end video editing decks, the wheel has two modes: jog (allowing you to “scrub” back and forth to find a particular point, similar to “rocking the reels” on an analog deck), and shuttle (a deluxe multispeed forward and reverse control allowing any speed from 1/4 speed to 10x speed). To help engineers find precise cue points quickly and efficiently, the M20 adds an analog Aux track, which acts as a “ninth track” to be used for this purpose. The Aux track has its own XLR input and output, and is recorded on a linear track near the top edge of the tape in the same manner that linear audio tracks are recorded on a VTR.

In addition, the M20 has an internal mixer that can record the output of any combination of tracks to the Aux track whenever needed. Simply select which tracks you want to copy, arm the Aux track, and press RECORD. Engineers can then creep the transport forward and backward to find exactly the start or edit point they need. The Aux track may also be used for slating and note taking, or as a click track. By combining the powers of the jog/shuttle wheel with the Aux track, the Alesis M20 provides all the advantages of digital recording with the convenience and control provided by analog tape and mag film… the best of both worlds.

New optional AES/EBU interface card
For facilities needing a digital interconnect besides the ADAT Optical port, the Alesis M20 features a slot on its back panel for installation of an optional AES/EBU interface card. This relatively inexpensive plug-in features eight XLR connectors: four stereo pair AES/EBU inputs, and four stereo pair AES/EBU outputs. These may be connected to digital video decks, digital mixing consoles, or external converters which use the AES/EBU standard.

The Alesis M20’s direct-drive transport is designed to provide the ultimate in tape speed and handling. Above is the reel motor assembly which handles the tape with servo-controlled care in all transport modes. Direct-drive capstan and full-servo reel motors, tension sensors, twin tach output and automatic head cleaning are a few of the drastic improvements offered by this robust transport mechanism.

A new remote/autolocator and meter display for professional applications
An entirely new remote control system has been developed for the M20. The CADI (Controller Autolocator Desktop Interface) offers capabilities that specifically cater to the needs of the recording professional. All the front panel controls of the M20, including the jog/shuttle wheel, are available on the CADI’s front panel. A bright, clear vacuum-fluorescent display shows machine status, and alphanumeric information such as the names of location points. The CADI can directly control up to eight Alesis M20s from its front panel, for a total of 64 tracks (plus time code and eight Aux tracks). Individual M20s may be taken offline from the remote, and individual LOCKED LEDs show when all machines in a system are in sample-accurate sync.

Unlike the BRC Master Remote Control used for the ADAT and ADAT-XT, the Alesis M20’s remote is not necessary for synchronisation to external SMPTE/EBU time code; CADI does not have an ADAT Sync 9-pin interface, or any other SMPTE or MIDI connection of its own. Instead, it connects to the M20 via a standard RJ-45 connector cable, the same type used for large computer networks. This new interface allows much longer cable runs between the remote and the recorders, so you can control M20s even if they’re in a machine room hundreds of yards away.

The same RJ-45 connection cable used for the remote also carries all the meter information back to a new optional digital remote meter display for the M20 system. This meter display has 32 meters, monitoring four M20s simultaneously, and its Peak Mode and Peak Clear mode may be set from the front panel of the Alesis M20, or from the CADI. In addition, eight LEDs on the front panel warn of any error conditions or tape problems