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Is Analogue Multitrack Recording Dead?


Now that affordable digital multitrack recording is available, is your analogue machine fit only for the museum? David Mellor asks, and attempts to answer, this question.


Have you ever seen the TV programme Troubleshooter, currently reincarnated as Troubleshooter 2, in which ex-chairman of ICI Sir John Harvey-Jones visits a company in difficulties and invents a package of rescue measures over a pint of beer in the local? As it happens he came round to see my modest recording establishment recently.

As is his way, he gave my factory and plant the once over and said something along the lines of, "I haven't seen anything as antiquated as this since I last visited Eastern Europe. If you are to compete with the best in the world then you have to have the best equipment." The worst of it was that he was looking at equipment only four years old, which I felt at the time of purchase had cost me an arm and the best part of a leg. Oh yes, and he also criticised my project management and the flow of materials across my factory floor — but he always does that anyway so I wasn't too upset.

I suppose I'd better own up and explain that this was only a dream — but Sir John's tie was just as vivid as real life.

I'll assume, as I always do, that my readers in Sound On Sound are serious about their music, and that if you are not making money out of it already then you one day hope to, perhaps as a career or perhaps simply as an absorbing hobby that pays for itself. Although the Troubleshooter 2 series will be nearly over by the time you read this, the inevitable repeat will make good viewing for anyone who wants to get the best out of any activity. For all his eccentricities, Mr. Harvey-Jones has a knack of hacking his way through to the central issue in any situation, cutting out any dead wood and making sensible plans for the future. Anyone with a personal recording studio would be well advised to consider what his or her objects and ambitions are, and to tailor their production facilities accordingly.

I can imagine three possible scenarios (there may be more):

You want to succeed in music. You decide that a personal studio would help you practise your art and provide the means to produce demo tapes of acceptable quality.

You have already achieved a degree of personal musical success. You have projects planned and you must have the capability of fulfilling these projects.

You operate a studio for hire and want to attract the best quality talent.

Decide which of these scenarios fits you best, and make that the starting point for any decisions you may make about equipment and facilities. I don't think it is productive, in terms of cash or personal satisfaction, to start by acquiring the equipment for its own sake and then deciding what to do with it. Note that I could apply my arguments to any of the equipment in the studio — even to the building of the studio and whether it should have its own coffee making facilities — but here I am going to consider only the multitrack recorder.

Since the invention of multitrack recording we have had, through necessity, to use analogue machines. Now there is one affordable digital multitrack available, the Alesis ADAT, and soon there will be another from Tascam. Next year we will also see Fostex entering the fray. If you have an analogue machine, should you trade it in now, even though it is still giving good service? If you don't have an existing multitrack to worry about, should you invest in digital equipment, or an analogue machine with more tracks for the same price? Let me help you decide...

DIGITAL ADVANTAGES



I don't think anyone is in serious doubt anymore that digital recording is better than analogue. Some people will say that analogue has its own special sound — which is certainly true. These people probably also prefer vinyl records to CD, and black and white television to colour. I would say that while it would be nice to have these old sounds available in an effects rack (along with the gritty distortion of optical sound on film), it is not appropriate, unless you specialise in the musical styles of a bygone era, to apply them to everything you record. 16-bit digital audio is a much more transparent information channel, even if it's not perfect yet.



"Digital recording is not perfect, but it's a damn sight better than any current analogue format other than Dolby SR used on professional equipment."


Even when working at its best, however, 16-bit recording is not always ideal. One day, digital recordings will be made at 24-bit resolution, and be very close to being absolutely linear (free of distortion within the 24-bit limit). For now, 16-bit digital audio is considered perfectly good enough for domestic stereo listening providing all the bits are used. But 16 bits are not quite good enough for mixing to stereo in the studio because you have no margin of error — it's virtually impossible to get full value out of that very last bit and drive the signal all the way up to 1111111111111111 (the highest value a 16-bit number can take) without going over the top at all.

By the way, if you want to see how bad some digital convertors are, record a sine wave tone onto your DAT and slowly reduce the level to zero. Now play the tape back, and as the tone diminishes, increase the monitor level to compensate. If the convertors are good then you will hear a noise building up which is smooth and even in character. On cheaper machines the noise will be harsh and gritty — not very nice at all. If the sine wave itself starts to become harsh then the convertors are not as linear as they ought to be. You'll probably hate digital after you try this!

16-bit multitrack is definitely not good enough, because each time you double the number of tracks you mix together the noise goes up by a theoretical 3dB. This means that 16 tracks of 16-bit recording will mix together to give the equivalent of 14 bits, in the worst case situation. The signal to noise ratio of the mix would in theory be 82dB rather than the 96dB (in theory once again) of each individual track. So, to be compatible with 16-bit stereo standards, a 16-track digital multitrack machine should record to 18-bit resolution.

It should be evident that as far as sound quality is concerned, digital recording is not perfect. But even so, I would still confirm my absolute certainty that it's a damn sight better than any current analogue format other than Dolby SR noise reduction used on machinery of a full professional standard. This last option can give 16-bit digital a fright, but only at a very considerable cost. As I shall be pointing out shortly, a digital multitrack recorder with A-to-D and D-to-A convertors of reasonable quality such as the Alesis ADAT is easily superior in sound quality to narrow gauge analogue machines such as the Fostex G and Tascam MSR models. It's not the fault of the analogue machines or their designers, it's just the way things are.

ANALOGUE FAILINGS



The problems with analogue recorders are too numerous to describe fully, but let me list some of them and explain the most troublesome in more detail. The problems with analogue multitracks include: crosstalk; counter slippage; drop outs; drop out gaps; edge track quality; end of reel runoff; gap scatter; head misalignment; head feedback; high frequency squashing; line up problems; reel scrape; modulation noise; noise; noise reduction problems; phase distortion; print through; record crosstalk; timecode problems; wow and flutter; tape wear.

Is this a long enough list? The biggest problem with analogue recording is, in my opinion, wow and flutter. Wow and flutter — a singular problem with two audible effects — is caused by manufacturing inaccuracies in the tape transport components on a microscopic scale. These inaccuracies cause the speed of the recorder to vary, causing either an audible wobble in pitch (wow) or a general dirtying of the sound (flutter). I once had a problem in this area with my multitrack that took a while to solve, and in the meantime my ears became so attuned to the phenomenon that I can now clearly hear W&F even on machines that measure within their specifications. Sampled piano and acoustic guitar are the worst instruments for showing it up.

The other major problem with analogue is the general dirtiness of the sound, caused by noise, modulation noise (noise that comes and goes according to the level of the signal) and drop outs. I suggested a simple tone test for digital recorders above, so here's one for analogue multitracks: record a 1kHz sine wave tone at 0dB on one of the edge tracks. (On any machine the edge tracks are usually worse than the others because the head to tape contact is not as reliable). Now play it back. The next thing you will do is probably write out an ad for the SOS Free Classifieds section to sell your machine at a knock-down price. Alternatively you could try the test, for comparison purposes, with a new machine.

In fact this will sound dreadful too, and all analogue tape recorders fail this test subjectively — the narrower the track they record upon, the worse will be the result. If you don't have an oscillator to produce the test tone then I'll tell you what it sounds like. The original crystal clear tone becomes muffled and uneven, there is a hissing sound clearly audible behind it, and there is a very obvious 'popping' noise at random intervals. The popping noise is, I believe, caused by very small dropouts which the ear misinterprets as sounds, rather than absences of sound. I have a very thick and expensive book on tape recording which fails to mention this ubiquitous phenomenon, so any more plausible explanations will be welcome.

A problem with the recorded sound itself is something you can learn to accept and ignore — after all, millions of recordings have been made on analogue equipment and sold to a generally satisfied public. It's more difficult to accept operational problems, because they affect your work again and again and you always have to find a way around them.



"Particularly on narrow gauge multitracks, crosstalk is evident between adjacent tracks and most noticeable at bass frequencies. It is reduced by noise reduction but not eliminated."


This isn't day-to-day line up, as would be done in a professional studio on an analogue multitrack. This is something a qualified service engineer would do on a regular, perhaps six monthly, basis. Probably the biggest alignment worry on an analogue machine is in ensuring that the heads are orientated at exactly 90 degrees to the direction of tape travel. Get this wrong and you wreak havoc with the frequency response. On a rotary head digital recorder the azimuth, as it is called, of each record/playback element is fixed at manufacture, and small discrepancies would not affect performance anyway.

Of course, a digital machine needs to be aligned too, but the meaning of the word is subtly different. This is because the digital machine records numbers onto the tape as a series of ones and zeroes, rather than recording a continuously variable signal. If these numbers can be read successfully then, within the limits of the sampling rate and resolution, the sound will be perfect. Look at it this way: 1234 has the value same as 1234, 1234 or 1234. Alignment in a digital machine involves setting the parameters of the control electronics for the rotary head so that the head follows the track accurately to give the best chance of retrieving all the numbers.

One of the most serious problems is caused by the need to align the recorder. Aligning the recorder simply ensures that the heads and electronics are matched to a standard test tape produced in carefully controlled conditions, the reason being that if you want to play on another machine a tape produced on your multitrack, you will want it to sound exactly the same. In the professional world, line-up is vitally important, as projects started in one studio will frequently pass through others along the way to the mix which will almost certainly be in the best mixing studio the producer can afford, within the budget. If the sound quality changes from one multitrack to another then problems — arguments even — are very likely to occur. In the personal studio, perhaps line-up isn't quite so important since the multitrack tape may never pass out of the studio door. Nevertheless, the performance of the machine will drift with time, and a tape recorded today may not sound the same in six month's time unless you have the machine realigned. (Note that the provision of alignment controls is in itself a cause of misalignment.)

CROSSTALK



When the conversation comes round to crosstalk, most engineers will recall an experience when they or the producer decided that one track of the recording wasn't really working and it could be dispensed with. The first move would be to pull the fader down — but the offending instrument, particularly if it was some kind of percussion, could clearly be heard in the background. It was then erased from the tape, but the result was no better — the sound was present at low level on other tracks.

Recorded crosstalk like this is one of the worst problems you can get, and if it occurs on your mixer then you need a new mixer which will make things a bit better. If it occurs on your analogue multitrack then you need to switch to digital, because crosstalk doesn't happen at all (apart from a minute amount in the electronics of the machine rather than the digits). Particularly on narrow gauge multitracks, crosstalk is evident between adjacent tracks and most noticeable at bass frequencies. It is reduced by noise reduction but not eliminated.

There is another kind of crosstalk that occurs in the record/playback head as you are recording. This appears predominantly at high frequencies and, although it doesn't affect the recording, it makes life more difficult for you by changing the frequency balance of the mix as you record. Obviously, recording a new part, artistically speaking, is all about the interaction between the instrumentalist and the parts already recorded on the tape. If the previously recorded tracks sound different to the way they should then this will inevitably affect the way the musician plays his part. Another point to mention is that if you try to bounce a recording onto an adjacent track, this type of crosstalk may cause howlround (feedback) in the head itself, which manifests itself as a high frequency tone of tweeter-blowing magnitude.

TIMECODE



If I may continue with the subject of crosstalk for a moment, anyone who has used timecode to synchronise a MIDI sequencer to tape will know that this awful sound tends to leak anywhere and everywhere, so a digital system which is not susceptible to crosstalk should be of great benefit. Timecode also causes 2-way crosstalk problems with the adjacent track — track 7, 15 or 23, depending on the scale of your facility. The first way is obviously that the timecode may bleed through to the adjacent track and appear in your mix. The other is that high level signals, particularly bass, may leak into the timecode and interfere with synchronisation. If your sequencer grinds to a halt when you try to record on the penultimate track, this is the cause of the problem.

The other problems caused by using timecode on a multitrack recorder include the loss of a valuable audio track and the fact that drop outs can cause the timecode to be intermittent. If you have suffered from intermittent timecode then you will know how unpleasant it is. One moment you are happily recording onto your sequencer, then it emits a rapid stutter of metronome clicks and stops. Since sequencers have, for some unaccountable reason, been designed to respond only to perfect timecode (or timecode translated into perfect MTC) you have a problem. The answer to this problem is to buy a synchroniser which will ride over any bumps in the code until good code emerges once again from the tape.

Now you have the problem that each time you want to stop the tape, the sequencer carries on for another couple of bars, because the synchroniser thinks it is compensating for a big drop-out! If you record timecode on a digital recorder as you would on analogue then not only will you be immune to crosstalk problems, drop outs do not exist (unless the machine is badly out of alignment or the tape is in an exceptionally bad condition).



"Other analogue advantages you will lose include spot erase, for ferreting out those unwanted clicks, and the ability to do real reverse reverb by turning the tape over and recording backwards."


EXTRAS



Should you decide to go digital, then at the moment you have two options: buy an Alesis ADAT now or wait a month or so for the Tascam DA88 near-equivalent. Now isn't the time to advise which to go for, but either way you will encounter a whole new set of circumstances. All of the analogue problems that I have mentioned and discussed will have gone completely out of the window, but will life now be perfect? Don't bet on it.

You will undoubtedly have noticed that the two affordable digital multitracks are both 8-track machines. In this day and age eight tracks are not considered to be nearly enough, and you may want to synchronise two to get 16 tracks or three for 24. With the ADAT, and apparently with the DA88, synchronisation between machines does not require any lost tracks for timecode. To its credit the ADAT synchronising is very quick and efficient compared to other systems I have seen and used. However, having said that it's quick, it is not instantaneous, and using two ADATs is definitely not the equivalent of operating a single machine. Tascam's product may be better on this point but it's too early to know. On the upside, using two 8-tracks synced together means that you have the ability to use one cassette for backing tracks and maybe several cassettes for overdubs, compiling the best overdubs later onto one cassette for mixdown. Remember that digital copying involves no quality loss.

Other analogue advantages you will lose include spot erase, for ferreting out those unwanted clicks, and the ability to do real reverse reverb by turning the tape over and recording backwards. Spot erase on the Alesis ADAT is hit and miss (although the forthcoming BRC controller may improve this) and if you need to record anything backwards, then it's back to analogue I'm afraid.

DIGITAL DOWNSIDE



If you want to use the Alesis ADAT or Tascam DA88 with timecode as they stand, then you will lose a track, which is a bit of a problem if you only have eight to start with. Fortunately all is not lost — Tascam are promising a reasonably-priced synchroniser card which will allow you to take full advantage of all eight digital tracks and have SMPTE at the same time, and with the ADAT you can either invest in Alesis' own BRC (which offers extensive facilities for multi-machine control) or a new budget sync box from JL Cooper. The latter translates Alesis' proprietary timecode, which emerges from the multipin connector on the rear panel, to MTC.

A CASE FOR CHANGE?



This is the big question. If you have an analogue multitrack now, do you trade it in for a digital multitrack, or a pair or threesome of them? In short I can't answer this question for you personally, but I can give you some food for thought:

"If it ain't broke, don't fix it", is an old and useful adage. If something is working well enough, then it's better not to tamper with it or change it because you might create problems you that don't have now. The problem with this way of thinking is that making progress is always going to be an emergency measure. You're going to have to wait until your analogue machine gives up the ghost and make the move into digital as a panic measure.

"I owe it to myself to have the latest equipment". Yes you do, but is it going to give you a tangible benefit? Many users of two-inch 24-track recorders haven't invested in Dolby A or SR noise reduction, even though it undoubtedly offers better performance, simply because they decided it wouldn't show any advantage on their bottom line, ie. how much profit the studio could make.

"I'm going to wait and see what happens in the next few months". Good idea, but will you ever stop waiting?

I can only speak for myself, but here is my serious and considered opinion on whether digital multitrack would be good for my personal studio: I fully intend to hang onto my existing multitrack for another three years. I only use it for my own projects, and it is still showing only a very low mileage. Digital multitrack may have an edge on sound quality, but that would mainly show up in terms of user convenience, rather than in the quality of the finished product, so long as I'm careful. That's my carefully considered opinion, but on the other hand, I have used a pair of ADATs and I have to say that I really liked them. I've set myself a goal of getting another three year's use out of my analogue multitrack, but how long will it be before the temptation to go digital is too much to endure? I'll tell you when it happens!

DO EIGHT DIGITAL TRACKS BEAT 16 ANALOGUE TRACKS?

Check out the prices: for the cost of an 8-track Alesis ADAT or Tascam DA88 you can have a Fostex G16 or Tascam MSR16, give or take a little. If you don't have a multitrack already then you have to choose: eight digital tracks or 16 analogue. Alternatively, if you trade in your existing 16-track analogue for an 8-track digital recorder, how are you going to manage?

Let's first of all assume that timecode is not a problem, either because you are not going to use it, or because you have adopted one of the solutions to the lost track problem outlined in the main text. You will have eight clear tracks of digital audio to compete with 15 or 16 analogue. For most of us these days, eight tracks are not enough for a finished recording so we are going to have to bounce down. If you were going to bounce on an analogue 8-track then you would record six tracks, then mix them to two, and then erase the original six tracks to clear them for your overdubs. This has obvious disadvantages because you lose quality in the bounce and you burn your bridges — there is no way of going back and correcting a track. With a digital machine, you could mix eight tracks into stereo on a DAT, then transfer them back to a clean section of the tape. The quality loss would be minimal, you can always go back if you really need to, and you get two extra tracks before you bounce.

Maybe this is not an ideal way of working, but it is certainly possible. I would say that it is worth serious consideration before deciding whether to go for 16 analogue tracks or eight digital.


THE DIGITAL FUTURE?

Be warned that what I am about to say is mere speculation. I don't have any 'inside' knowledge other than an interest in what might or might not, be technically possible in the not-too-distant future.

The Alesis ADAT uses a large S-VHS tape to record about 40 minutes of 8-track audio. The Tascam DA88 uses a smaller Hi-8 cassette to record 100 minutes of 8-track. The discrepancy in sizes and playing times indicates to me that there is room for more tracks in both of these formats. I would speculate that Alesis will produce, maybe in 18 months or two years time, a 16-track ADAT recorder. What's more - if they have taken a hint from Sony's upgrading of their much more expensive 24 track digital recorder to 48 tracks on the same tape with 2-way compatibility — you will be able to play existing 8-track ADAT tapes on their 16-track machine and record the other eight tracks in the gaps. And when you have finished doing that you will still be able to play the original eight tracks on your 8-track machine.

As for Tascam, I doubt whether this type of compatibility will be possible given the smaller size of the tape. I imagine that they will produce a 16-track machine that uses the same tape to record for half the 8-track duration, ie. 50 minutes. It will of course be able to play and record to the 8-track standard as well.

I hope you find these speculations interesting, but please remember that this is all they are. I don't have a crystal ball and there's certainly no way anyone at Alesis or Tascam would let me into secrets of this magnitude.


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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - Feb 1993

Feature by David Mellor

Previous article in this issue:

> Small But Perfectly Formed

Next article in this issue:

> Yamaha RM50


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