HARD CHOICES & SOFT OPTIONS

Choosing A Recording Setup: Part 4

Published in SOS October 1998
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Technique : Recording/Mixing

CHOOSING A RECORDING SETUP

PART 4: Just when you thought it was safe to dip your hand in your pocket and buy that ideal studio, PAUL WHITE throws digital mixers into the frame.

Last month, I looked at various combinations of MIDI and recording gear that could be used to set up a studio, and as you've probably gathered by now, it's not a simple question of analogue or digital, but rather picking the best machine for the job in hand. Now we have digital m

SAMPLE RATES Digital studios can occasionally throw up problems when different pieces of gear want to run at different sample rates. For example, if you have the old black-face ADATs that can only work at a 48kHz sampling rate, the rest of your digital studio must be set to run at 48kHz too. But as you can't mix sample rates in the digital domain without a sample rate converter, what then happens if you want to bring in an audio file taken from a sample CD at 44.1kHz? In this case you have three possible options: * bring the signal in via an analogue input; * bring it into a computer that has a sample rate conversion facility; * use a real-time hardware sample asynchronous rate converter such as the now-discontinued Alesis AI-1.

ixers to add to the equation, but what's the right reason to buy one? On close examination, they seem to give with one hand and take away with the other. For example, having dynamic or even snapshot automation of all levels, effects and EQs is appealing, while moving faders look very cute. But it would be a mistake to think that just because a mixer is digital, it must therefore be better than analogue. In fact, the real reason mixers are going digital is because it's now got to the point where it's cheaper to build an automated digital console than an automated analogue console -- and it's the automation that everybody wants.

I've tried out a few low- to mid-price digital mixers, some of which are exceptionally good notwithstanding their ludicrously low price. However, I think I'd be fair in saying that digital EQ currently leaves a lot to be desired when compared with the analogue equivalent, even though the digital model may offer no less than four fully parametric bands. Deficiencies in the EQ department may not worry you if, say, you have a nice outboard unit you can use when the going gets tough. However, this can beg the question of how you plug it in. Low-cost digital mixers are only low-cost because everything is done in the digital domain, and that means few, if any, analogue insert points. And while some low-cost digital desks have insert points on the analogue inputs, so you can patch in effects while recording, these aren't available when you go in digitally.

There's a lot to be said for having a digital multitrack recorder connected to a digital mixer via a fibre-optic bootlace in terms of keeping the signal clean, but you may find you've created a virtually closed system that forces you to use the processors, effects and EQ provided within the mixer rather than giving you the freedom to patch in whatever does the job best, as you could with an analogue desk.

Furthermore, you may have to dig deep into the operating system to adjust all these inbuilt effects and processors. Another of the cost-saving features of digital design is that you have fewer knobs to access a greater number of functions, so most of the time you can find yourself wandering around 'menuland'.

In defence of small digital mixers, the automation is wonderful, not necessarily because you always want to automate every aspect of a mix, but rather because they let you recall a session and get back all the level, pan, EQ and effects settings you had at the time. What's more, the effects built into some of these mixers are pretty serious. When you compare them to the cost of the analogue alternative (even with basic VCA automation), plus a couple of half-decent effects boxes, there's really no contest. As always there are pros and cons. The trick is to use the technology for what it does best and to find ways around its limitations.

One possible approach is to connect the multitrack recorder via a digital desk's analogue inputs, even if the multitrack recorder is digital and has a perfectly acceptable fibre-optic interface compatible with the desk. Rather than connect it directly, you go via a normalised patchbay, which functions as a set of analogue insert points when you're mixing. If you want to add outboard compression or some other process during recording, an

"The trick is to use the technology for what it does best and to find ways around its limitations."

d the desk itself has no insert points, it's a simple matter to use an outboard mic preamp before your compressor, or even go the whole hog and record using a 'voice channel' type of product patched directly into the multitrack's inputs. This may involve a little repatching, but it should produce better results than using the mic preamps and digital processor in a low-budget digital mixer. Figure 1 shows just such a setup. If this unnecessary digital-to-analogue and analogue-to-digital conversion seems sacrilege, there's no reason not to leave your fibre-optic link in place and switch from using analogue to digital inputs when you don't need to insert an external device. Of course, if you're using an analogue recorder such as an open-reel multitrack, then you'll have to go in analogue anyway, but you'll still need the patchbay to give you insert points on mixdown.

Though combining analogue with digital may seem an odd way to go, I think most studios will use a mixture of the two technologies for the foreseeable future. There's a lot to be said for using an analogue tape machine with a digital mixer or even a digital tape machine with an analogue mixer, since an all-digital signal chain still tends to sound over-clinical, especially to those people brought up on the sound of analogue tape and recordings made in analogue studios.

Indeed, the main benefit of putting together an all-digital system linked exclusively by digital means is not necessarily the sound quality, even though keeping everything in the digital domain is technically neater. Almost of equal importance is the fact that using fibre optic links cuts down on wiring, and if you're satisfied with the effects and processors inside your digital desk, then you can set up a very compact, tidy system that is immensely powerful.

A digital mixer used as part of an otherwise all-analogue system may be configured in much the same way as a normal analogue console. As soon as you add one or more pieces of digital equipment connected in the digital domain, there's the issue of synchronisation to consider. For digital systems to work together, not only must their sample rates be the same, they must also be synchronise

"There's no single 'right' technology, but rather an array of choices, and the best solution for one user may not be the best solution for another."

d to the same sample clock, otherwise there will be audible ticks and glitches as the sample rates of the two devices drift relative to each other (this subject is addressed in far greater detail in Hugh Robjohns' Digital Basics article on page 232). However, the basic rule is that only one device can function as a master and all the others become slaves set to external sync mode as in Figure 2 (Yamaha have tried to simplify this by making mixers such as their 03D capable of working out for themselves whether they should be master or slave). In a system comprising a digital multitrack recorder and an external digital signal processor connected to the mixer via a digital link, the recorder would normally be the master, with the mixer and effects processor functioning as slaves.

In more complex systems, clocking errors can occur from daisy-chaining too many pieces of gear together, in the same way as MIDI instruments misbehave if connected to the end of a long Thru chain. In such a system, it's better to use equipment that can sync to word clock and then feed word clock to each from a master generator, such as an Alesis BRC, as shown in Figure 3, right. Unfortunately, not all the equipment used in a typical project studio has the facility to work with word clock, so it may be necessary to adopt a hybrid approach.

COMPUTER-ADAT LINKS If you have a system based on ADATs or ADAT-compatible recorders along with a computer running audio software, it's most definitely worth considering adding a computer interface that can transfer data from the ADAT to the computer and vice versa in the digital domain via a fibre-optic Toslink cable. This really brings you the best of both tape and computer worlds by allowing you to move material from tape, edit it, and then return it to tape exactly where you want it.

To synchronise a sequencer to a conventional analogue tape machine, it's necessary to use one track of the analogue tape to record timecode via a sync interface that converts the timecode into a form that can be recorded as an audio signal on tape. The two common sync formats are SMPTE and MIDI Clock, though most interfaces now convert SMPTE to MTC (MIDI Time Code), which is supported by the majority of serious modern sequencers. MIDI Clock is still used on some budget equipment, but providing the sync interface exploits MIDI Song Position Pointers, it works perfectly well. Without SPPs, the song must be started from the beginning each time the tape is stopped.

In theory, you could record timecode on to one track of a digital disk or tape recorder in exactly the same way, but that's seldom necessary. More often, a dedicated interface is used to convert the timing sub-code from the recorder to SMPTE, MTC or MIDI Clock so that a sequencer can be locked up without having to waste an audio track. Indeed, some dedicated hard disk recorders have MTC output as standard and can also chase lock to MTC. Unfortunately, the manufacturers of digital multitrack tape recorders rarely include an MTC output, so some form of additional interface or card is necessary. With the Alesis ADAT for example, equipment such as the Alesis BRC (or a third-party interface) utilises the data from the nine-pin sync socket on the back of the tape machine to derive the required timecode.

Hopefully this series has helped you put the various recording options into perspective. As I said at the beginning, there's no single 'right' technology, but rather an array of choices, and the best solution for one user may not be the best solution for another. What you need to do is think carefully about what you want to achieve and how you best like to work, then choose your system components on that basis.

Next month, I'm going to describe a system that I put together combining hard disk recording, digital tape and both analogue and digital mixers. Some of the things I've done are slightly out of the ordinary, and I'm sure that some changes and additions will be made before I'm finally happy with it, but at least it might provide a useful case study that gets you thinking in different directions.

Recording Options: Choosing A Studio Setup Part 1

Recording Options: Choosing A Studio Setup Part 2

Recording Options: Choosing A Studio Setup Part 3

Recording Options: Choosing A Studio Setup Part 4

Recording Options: Choosing A Studio Setup Part 5