ADAT: Power User's Guide

Armed with a bunch of Alesis technical papers, Paul White unravels the mysteries of those inscrutable error messages, the secret button combinations and the finer points of ADAT tape care.

Digital multitrack is a wonderful concept, but because it is digital, there's a tendency to expect it to be bomb proof — and of course, nothing is. ADAT's format is very robust but, like most digital audio systems, it has an error‑correction system which is so powerful that you may never notice things are going wrong until you hit a major problem such as an irretrievable dropout. Aside from keeping your kids from using your ADATs as repositories for partly‑eaten toast, you can ensure your system runs smoothly and reliably just by observing a few tape care rules and learning what the error messages actually mean.

Like any piece of precision electro‑mechanical equipment, ADATs need to be treated with respect. It helps to cover your ADATs with a dust sheet when they're not in use, and if they're rack mounted, leave ventilation spaces to prevent the units from overheating. Those taking ADATs on the road should ensure that they don't get jolted around by using suitably designed crating, and measures should be taken to prevent the ingress of dust or damp.

Most of the time, your ADAT should behave perfectly, but just once in a while, you might see the tape position display being replaced by an error message. Hopefully, this will be an infrequent occurence, but if an error message should appear, what does it actually mean and what, if anything should you do about it?

( ‑du‑ ): This signifies excess humidity, which may be caused by condensation when, for example, moving the machine from a cold vehicle into a warm room. If this error is present, the tape will not thread into the machine and the ADAT cannot be used.

Action: Wait for ADAT to dry out.

( ER 2 ): Signifies a tape‑threading problem.

Action: The tape will‑self eject when Error 2 shows, so check that it is not damaged and try again.

( ER5 ): Usually appears when the ADAT is being asked to run outside its permitted speed range when sync'ed to an external source via an AI‑2 or BRC. This can happen, for example, if the ADAT is sync'ed from a U‑matic video via a BRC and the video is played at slow speed for editing purposes.

Action: The error message will disappear when code within the specified speed range is fed to the BRC. If this error appears when no external sync source is being used, refer to Error 8.

( ER7 ): Signifies that the ADAT's error correction system is having to correct an unusually large number of errors. The first sign of excessive error correction activity is a blinking decimal point in the right of the display window, and when the situation becomes more serious, Error 7 puts in an appearance. If this happens infrequently, it may be due to a drop‑out on tape. If the message appears more frequently, there is a possibility that the tape is faulty or damaged, and it would be prudent to clone it to a new tape, using a second ADAT, before it deteriorates to the point where it may not play back reliably. The error correction software from the master machine will allow the copy to be as good as the original.

This type of error may also show if the ADAT's heads have become contaminated with dirt or oxide shed from the tape. Do not open the machine or attempt to clean the heads, as there is a high risk of damaging them. Similarly, don't run conventional head‑cleaning tapes. The Black Watch cleaning tape from 3M may be used in the machine, but this shouldn't be run any more than necessary — that is, when an error message indicates that cleaning may be required.

Action: If error message is persistent, try the machine with a different tape. If the message disappears, the chances are that the original tape is giving problems and needs to be cloned without delay. If the message appears with all tapes, run the 3M Black Watch head cleaning tape for just 10 seconds and then try again.

( ER8 ): Shows when the ADAT loses sync, or the sync read head is unable to read sync information from the tape. This may be due to a variety of causes, including poor connections between machines or between ADATs and BRC, bad sync cables or bad tape.

Action: If this message only shows occasionally, there's nothing to worry about, but if it becomes a regular feature, try the following: check that the system works OK with a different tape. If it does, suspect tape problems and clone your original as soon as possible. If the fault persists, try running the Black Watch head cleaner tape for 10 seconds. If you're still not out of trouble, check over the wiring, particularly the sync cables. Some home‑made sync (9‑pin) cables seem to cause problems, so if in doubt, buy some genuine ADAT sync cables. All sync cables should be screened, with the screen connected to the D‑plug chassis at both ends of the lead. The plugs are wired pin 1 to pin 1, pin 2 to pin 2 and so on.

ADAT And Tape

When ADAT was first launched, Ampex 489 S‑VHS tapes were strongly recommended for use in the machine. This is because other brands may produce higher error rates or may be prone to shedding oxide onto the tape heads, but further research has seen a few other brands added to the approved tape list. While Ampex 489 is still the 'official' ADAT tape, it's also OK to use:

• Ampex 289
• Maxell XR‑S Black
• JVC XZ
• TDK SP.

I've also used 3M Master Broadcast S‑VHS tapes for some time with no problem, and I've heard good reports about Zonal SE180.

A 180‑minute (PAL) tape gives around 40 minutes of recording time, but what you may not know is that up to 58 minutes of recording time may be obtained by using a 240‑minute (PAL) tape. Maxell's XR‑S 240 tapes seem to be fine for this job, but life isn't as simple as putting in a longer tape and hoping for the best. If you do, you run the risk of drop‑outs, as the tape tension will be incorrect — your ADAT needs to be told that it's being fed a 240‑minute tape.

To set up an ADAT to work with a 240 tape, press the Set Locate and Format buttons simultaneously before formatting the tape. This selects T160 mode as opposed to STD, but as the machine defaults to standard mode on power up, you need to remember to select this mode every time you switch on intending to use long tapes. You should also bear in mind that long tapes are unlikely to be quite so reliable as 180s. Under no circumstances should 'cheapo' tapes of either length be used, as these may well clog up the heads, and note that you can't format a video tape that has already been used to record video material — it's strictly virgin tapes only.

Just because video tapes come in cassettes doesn't mean they can be treated casually. Dropping the tapes can damage them, as can leaving them exposed to dust, heat or damp. Never leave any type of tape exposed to direct sunlight, especially behind glass, and always rewind the tapes at the end of a session, before packing them away in their protective boxes. You should also store tapes away from strong magnetic fields, but the last time I experimented with a video tape and a tape head demagnetiser, I was unable to affect the recording in any way, so unless you plan to take your tapes into an MR scanner with you, you shouldn't have to worry unduly on this score.

Lock‑Up Time

Some users complain of the apparent long lock‑up time when two or more ADATs are used together, though in fairness, this is comparable with the lock‑up time of two analogue multitracks. With version 3.06 ADAT software, the lock‑up time should be about 1.5 to 2 seconds, though not all machines in a multi‑machine system will lock up at exactly the same time, as they're all locking independently. Sometimes it can take longer to re‑establish sync after winding a long way through the tape, and you may notice that some ADATs appear to be fast winding rather faster than others. This is generally due to a difference in tapes, but if you take certain basic precautions, these differences can be minimised.

Firstly, it makes sense to use the same brand and length of tape in each ADAT. Furthermore, before switching off at the end of a session, all tapes should be fast‑forwarded right to the end before being fully rewound to the start. This encourages the tape to spool properly, which is important, because in a real‑life recording session, you may be shuttling back and forth over the same piece of tape many times; this promotes an uneven wind, resulting in increased winding friction and longer wind times.