Those of us who can afford it probably master to DAT, but for the ADAT user, this isn't necessarily the best option, as Paul White reveals.
DAT has established itself as a standard stereo mastering medium in both the semi‑professional and professional markets, but as any long‑time DAT owner will tell you, most of the cheaper domestic models don't hold up too well to regular studio work, while the more serious DAT machines cost in excess of £1000. For the ADAT user, there's another option, and that is to master to two spare tracks. Most of these techniques apply equally to Tascam's DA88, but because I have more experience with ADATs than DA88s, I'll continue this brief article by referring mainly to ADAT.
Why Do It?
OK, so why is it useful to mix to two ADAT tracks? After all, the sound quality is about the same as you'd get from a good DAT machine. From a practical viewpoint, if you mix directly onto two tracks of your multitrack, the master stereo recording and the original tracks are always in the same physical place so it's easy to keep track of your material. Furthermore, if you have two or more ADATs, when you clone your master tapes for safety purposes, you also clone your masters.
But there's a far better reason, and that's the fact that the Alesis ADAT and Tascam DA88 handle drop‑ins or punch‑ins by creating a very rapid crossfade, which results in a seamless, glitchless transition from one section to the next. In the context of mastering, this means that if you've done a mix and it hasn't all gone according to plan, you don't have to go back to the top and do it all again — you can simply set up your mixer to correct the offending part and then punch in and out at the appropriate places. Most of the time, a manual punch‑in/out will be fine, but if you have the capacity for automated punch in/out, then you can be as surgical as you like.
When you weigh it up, working in this way can help you to achieve the sort of results normally associated with automated mixing — any song can now be mixed in as many different sections as you like. An example of this might be a song where you require a different mixer setup for the choruses and yet another for an instrumental solo. A sensible approach might be to mix the whole song in one pass with the mix set up for the verses, then go through again dropping in all the choruses with the chorus mixer setting. Finally, the solo can be replaced with the correct mix.
DAT Limitations
A serious shortcoming of DAT when it comes to mastering is that you can't easily top and tail songs (erase unwanted material at the start and end), and you can't change the order of the songs or introduce precise spaces between tracks. With digital multitrack, the automatic punch‑in/out (or even manual if you're confident) can be used to record silence right up to the start of the song and again at the end, and if you have two or more multitracks, you can digitally transfer your mixed masters from one machine to the other in any order and with appropriate gaps between tracks. ADAT/BRC users are particularly well catered for when it comes to working this way.
Every silver lining has its cloud, and in the case of both ADAT and DA88, you can't just digitally clone from your pair of tracks to a DAT machine to produce a DAT version for cassette or CD duplication. In my own case, I use the Alesis AI‑1 interface, which not only provides a digital (SPDIF) output of one pair of tracks at a time, it also converts the sample rate to either 48kHz or 44.1 kHz, even if the ADAT has been used in varispeed mode. This makes it easy to get the stereo master either onto DAT or into a hard disk editing system, should you need to do any further work on the material.
Those without an AI‑1 must either employ the services of someone who has such a system to create a DAT clone (and this only has to be done once per album, so it needn't be expensive), or resort to using the analogue outputs. In practice, the loss of quality due to copying once via the analogue domain is usually so slight as to be negligible. You could even go via something like a valve compressor, or other enhancement device, to add a touch of post‑production sweetening.
If you're already mastering to DAT and you're happy with the result, there may be no compelling reason to change, but it's nice to be aware that the option is there when you need it. I was once faced with the task of putting together someone's live album from a multitrack tape, and to make it more complicated, each song flowed into the next with no breaks. I had no automated mixer, so I copied their multitrack analogue tape to my ADAT setup and did exactly as described here. Had I tried to complete the job in a single pass, I'd probably still be mixing it now!