ADAT, ADAS or ADAP? - You could be forgiven for being confused by the choice of digital audio systems currently available. Vic Lennard attempts to shed a little light...

The appearance of ADAT in January 1991 at the Los Angeles NAMM Show, and the subsequent reports on its specification and capabilities, caused quite a stir in the music industry. For less than the price of a 16-track analogue multitrack recorder, here was an 8-track digital machine running on low-cost S-VHS tape. And there's been no secret about Tascam's intention to launch a similar recorder - at a not dissimilar price - but using the Video-8 tape format.

On the other side of the coin there is currently a variety of direct to disk systems running on the PC, ST and Apple Mac as well as freestanding units such as the Akai DD1000, Plasmec ADAS, Roland DM-80 and Yamaha CBX-D5. Clearly, there's never been a better time to start thinking about going digital - but how do you decide which system is best for you?

TAPE-BASED SYSTEMS

Digital multitrack recorders have been available for some years - at a price. When Akai launched A-DAM, a 12-track 'budget' unit using Video-8 tape, it broke a number of barriers at £20,000 when balanced against comparative recorders from Sony and Mitsubishi. ADAT from Alesis is the first of the next generation of price-breaking digital recorders, costing around £3,500.

Compared with a direct to disk system, the tape-based recorder has the immediate advantage of price. Part of this is down to the relatively cheap medium of tape and the fact that the system works without the aid of a computer, monitor and hard drive. In terms of pure audio quality, there should be little to choose; although the tape is used, it is handled in a similar way to DAT and therefore should generate no tape noise.

However, the fallibility of tape has to be considered, as flaws can occur in spite of rigorous quality control checks, and such faults will not be heard until playback.

When it comes to comparing the audio quality of a digital recorder with that of an analogue machine at this end of the market - you simply can't. The budget 8- and 16-track machines from Tascam and Fostex are undoubtedly excellent value for money, but their sonic quality is certainly coloured in the low and high frequency ranges. While Dolby S has gone a long way to improving the inaccuracies of both dbx and Dolby C, a multitrack digital recorder should be capable of exhibiting a far superior audio performance.

At current prices, eight tracks on ADAT is a little cheaper than 16 tracks on a Tascam or Fostex analogue recorder. But then, your decision may not come down to audio quality; it may be a simple fact of life that you need 16 tracks for recording. This is still possible using two (or more) ADATs synced together, but of course, at double the price. I suspect, however, that many ADAT recorders (and the Tascam equivalent when it surfaces) will find their way into MIDI-based studios whose primary requirement is for the recording of high quality vocal and acoustic instrument tracks to accompany the virtual tracks played back via sequencers.

It also has to be remembered that the maximum recording time is restricted to the tape capacity - though in the case of S-VHS this is not likely to be a problem. However, the use of any tape means that cueing to a particular part of a song does take time, but, of course, this will be less on a small 'cassette' based system such as S-VHS than it is on a reel-to-reel machine.

DIRECT TO DISK

In the last year or so, it has become commonplace to see direct to disk recording systems as an extension to sequencing programs on a computer. Studio Vision, Digital Performer and Cubase Audio all require an Apple Macintosh with a sampling board, (based around a Digital Signal Processor DSP) installed in the computer. Standard is two tracks of audio, but by using special sampling boards, this can be increased to eight tracks and beyond. Digidesign's Protools is a good example of a true multitrack system, but eight tracks will cost about £14,000 - in addition to the cost of the Macintosh and hard drive(s).

The main advantage of such a system is that to all intents and purposes, the digital audio is simply another track (or pair of tracks if you're working in stereo) on-screen. These can be viewed and treated in many ways like those containing MIDI information. By opening up an Edit window for a digital audio track, you are presented with the audio waveform instead of a list of MIDI events, and it is possible to carry out cut, copy and paste routines from there. Using this system, you could record a vocal part, trim off the beginning and end and cut up the remainder to precisely fit the MIDI data recorded on the same sequencer. This highly visual approach is not to be underestimated - but remember, digital audio cannot be mixed and then unmixed in the way that MIDI data can.

"Most of us would love to have an 8-or 16-track direct to disk system with full random access of tracks, and cut, copy and paste facilities - but is it something we actually need?"

Yamaha launched the CBX-D5, a 4-track digital recorder at the Frankfurt Show this March and in doing so introduced an interesting idea. The system requires a computer-based program to provide a remote control facility and both Steinberg (with Cubase Audio) and Mark Of The Unicorn (with Digital Performer) are providing the necessary software for the ST and Macintosh respectively. Other companies may well follow suit, especially with the launch of the Atari Falcon (see last month's Newsdesk) which has an in-built DSP - and an extremely low price tag.

With the use of a hard drive to record data, the maximum time allowed is directly proportional to the size of the drive itself - with approximately 10 Mbytes being required per minute per track of stereo (16-bit audio, recorded at 44.1 kHz). Of course, hard drives are now available with capacities measured in Gigabytes - or thousands of Megabytes - so maximum recording time isn't a problem, although price is!

There are also various stand-alone systems which work with or without a host computer. The Plasmec ADAS system is now multi-platform, and as such, can be used on the ST, PC, Mac and as a freestanding unit. It only provides a 2-track system, which is fine for editing or spooling-in vocals etc, but cannot be used for multitracking purposes.

Other similar offerings come from Hybrid Arts, with ADAP and Digital Master on the ST, and Digidesign, who produce Soundtools on the Mac. Such systems may be capable of using removable Syquest cartridges - a relatively low-cost alternative to the fixed hard drive. The standard capacity is 44 Mbytes which allows a little more than four minutes stereo recording at CD quality and 88 Mbyte cartridges are now becoming available. Typical price for a Syquest drive is around £350-400, with cartridges retailing at about £50.

Another possibility is to use a Magneto-Optical (MO) drive which utilises a CD-style cartridge. The standard version has a capacity of 650 Mbytes, but uses a single-sided drive which means that the cartridge has to be turned over when one side is full. Still, this gives around 30 minutes of stereo, CD-quality digital audio per side, the drives costing around £2,500 and the disks about £200.

Roland's DM80 is a true, multitrack direct to disk recorder with the 8-track version costing just under £8,700 - including the remote controller and two 100 Mbyte hard disks as standard. The system is aimed squarely at the high-end professional user and Roland have now developed software for the Macintosh which acts as a remote control system.

Akai are currently developing the HDR100, a 4-track system which can be expanded to 16 tracks. The starting price for four tracks will be around £1,400, but this does not include a controller or the hard drives. Other Akai products include the evergreen DD1000 - which can record on two tracks and playback on four and uses an MO drive - and the version 2.0 software for the Akai S1100 sampler which allows for 2-track digital recording thanks to the S1100's onboard DSP.

Balancing the pros and cons of a stand alone unit and a computer-based system is difficult. While direct to disk recording via a computer has the advantage of easy incorporation into a sequencing program (and so very little extra to learn), it has the disadvantage of the fallibility associated with a non-dedicated system. For instance, the Apple Macintosh has its operating system installed onto hard drive and so can be damaged by system crashes - often without the user realising it. This can lead to programs freezing, or locking up, a situation which is far less likely to occur in a stand-alone unit. A further disadvantage is the need to regularly clear the hard drive by dumping data to a tape based medium such as DAT.

The cost involved in multitrack direct to disk systems also needs to be taken into consideration and would preclude their use by all but a select handful. However, many of the 2-track systems are affordable, especially if they run on your existing computer. Like many things, it is very much a question of need versus desire. Most of us would love to have an 8- or 16-track direct to disk system with full random access of tracks, and cut, copy and paste facilities. But is it something we actually need?

With the advances in MIDI, many studios use their multitrack recorders less and less. These days even backing vocals can be recorded onto a sampler and triggered from a sequencer, thereby cut out a generation of signal degradation. The release of ADAT is likely to make many of us consider the option of recording all of our various instruments onto eight tracks doing any tracks, bouncing as and when necessary. On the other hand, the fact that up to 16 ADAT recorders can be linked together to give a maximum of 128 tracks is also interesting...