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Masters Of The Universe

So you wanna record an album? Anyone with a DAT recorder can make what they think is a usable master tape, but it takes a little know-how to do it properly. Mastering engineers Mike Brown and Martin Giles of CTS Studios explain what goes into preparing master tapes for tape, record and CD duplication.


The Cutting edge of technology: a laser 'cutting' machine exposing a light-sensitive glass disc to produce a CD Master.


Recent years have seen a revolution in the technology available to musicians and recording studios. The cost of signal processors and electronic sound sources has fallen dramatically. Happily, this has brought the recording of relatively sophisticated music within the financial reach of many more people. Indeed, there has been a proliferation of 'home studios' based around a sequencer with a few samplers, expanders and drum machines, all synchronised to a small multitrack machine, with a DAT (Digital Audio Tape) recorder to record the final stereo mix. In some cases this has meant 'professional' equipment being used by people with little training or experience in how to get the best out of it. One area where people are quite often ignorant seems to be that of the disc cutting process, the process by which your stereo mix is turned into a master from which vinyl album or CD copies are produced. Perhaps the audio industry itself is at fault... This article has been written in an effort to put this right.

DISC CUTTING



Originally the disc cutting process was the recording. After the optimum positions for the microphone(s) and performers had been agreed the sound was cut directly to disc and that was that. Later, with the development of magnetic tape the disc cutting process became more of an afterthought, almost a formality, albeit an essential one. Certainly classical engineers and producers, especially at Decca and EMI, were aware of how important was the cutting process to getting a good copy of their work into people's homes, but in the early '60s pop engineers and producers rarely gave it much thought. Many a hit single was recorded straight to mono in a 3-hour session from 10am-1pm, the A & B-sides would be chosen over lunch, and the tape sent to the cutting room in the afternoon! Cutting Engineers were thought of as back-room boys. Producers had no interest in attending the cut, much less artists. It was, after all, only a transcription process; their work, including any editing, had already been done by that stage. So, historically, little was known about the art of disc cutting, apart from those few who actually practised it.

During the late '60s and early 70s pop recording developed almost out of all recognition, first 4, then 8, 16, and soon 24-track recording. This meant a whole new approach to recording, because instead of simply recording a performance, songs were built up, layer upon layer, often over quite a considerable time, and maybe at a number of different studios by a number of different engineers. All this meant that more flexibility and creativity was available to producers and artists, who also became much more aware of exactly what was going on technically. This technical awareness also began to extend into the Cutting Room. Producers and artists began to wonder exactly what could be done by the back-room boys who had been left to their own devices for so long.

And so we come to the present day. Technological evolution continues apace, but the role of the Mastering Engineer (as disc cutting engineers have become known) is still just as important and probably just as mysterious as ever.

THE ROLE OF THE MASTERING ENGINEER



In theory, disc cutting should be just a simple transcription process. In practice, however, things are often quite different. Experience has shown that much can go wrong before a tape even reaches the cutting room and that absolutely nothing can be taken for granted. A mastering engineer will first listen to a tape and consider two points immediately. Firstly, is there anything wrong with the tape? (Any faults, drop-outs, crackles etc.) Secondly, is it the right tape? (Does it have the right versions of the right songs?) If we're OK so far then we can start to make more artistic judgements, like whether the tape would benefit most from being transferred 'flat' or whether a little equalisation is called for.

Each tape is considered on its own merits. There are many reasons why a tape may need a little EQ when it is cut or transferred for CD. Often it may be that the sound on tape is not quite what the engineer/producer/artist ultimately wanted, and this may have become apparent since the tape was mixed (especially if the mix was done at four in the morning). In some cases the fresh ear of the cutting engineer may be able to bring out something which those who have been involved more intimately may have overlooked. In the case of an album a little EQ on some tracks may make the subtle difference between a record sounding like an album rather than a collection of individual mixes.

It's probably worth saying at this point that although some people feel that mastering engineers like to give their 'sound' to each record they cut, this is not in fact the case. If, to you, the mastering process is an arcane art practised by 'Magic Disc Cutting Fairies' in dark mysterious rooms, perhaps you should consider attending your next cut to see what goes on and why. It may cost a little more but the knowledge gained will prove invaluable to you in the future.

IN SEARCH OF THE PERFECT TAPE



Suppose you are recording your own album, and want to prepare a master tape from which CDs and records can be mastered and pressed, or tapes duplicated. What is the ideal tape; what is it that mastering engineers expect? Simply, a tape which sounds exactly the way you want it to. Ideally you will have mixed your tape using monitor speakers you know well and understand. You will have taken care with the levels and dynamics, recording each song at a level which does not require any adjustments to be made between songs. After this you will have edited the songs into a final running order with suitable gaps between tracks, as required.

SPECIFIC PROBLEM AREAS



As far as the vinyl disc is concerned there is only one real 'no-go area' and that is out-of-phase bass. When mixing you should try to keep in the centre of the stereo image anything which is likely to contain frequencies below about 200Hz. Any out-of-phase information is cut into the groove vertically, and if it's bass-end it produces a ski-slope of a groove which usually causes the playback stylus to lift out or jump. Another problem are is excessively sibilant vocals, which can also produce a cut which most stylii are unable to track cleanly, resulting in a 'tearing' type of distortion.

MAXIMUM PLAYING TIMES



The questions that mastering engineers are most commonly asked relate to maximum playing times. 7-inch singles can be almost any length. 'Hey Jude' was over seven minutes, but that was The Beatles for you. If you want to get your single played on the radio then it's still a case of 'the shorter, the better'; preferably under three minutes. Anything over 3:45 will probably have to be cut at a slightly lower level to eliminate the possibility of the record jumping on some record decks.

With 12-inch and CD singles almost anything goes, but remember the BPI have stipulated 20 minutes as the maximum total time for an entire single. Any record which runs for more than 20 minutes isn't a single as far as BPI and Gallup are concerned!

Vinyl LPs tend to suffer from level reduction at the cutting stage after the sides exceed about 23 minutes. It's hard to be precise about this because it does depend on the kind of music and the bass content. The restriction here is a physical one defined by the lower dimension limit for LP grooves laid down by the British Standards Institute.

CD albums have an upper time limit of 74:40, according to the spec of the format. Some CD plants may be prepared to manufacture discs lasting up to 79 minutes but may require a disclaimer from you absolving them of any responsibility for playback problems caused by exceeding the Philips CD specification.

Cassette running times can be up to 45 minutes per side (ie. 90 minutes in total) but duplication costs will vary according to length. Note that the two sides should be roughly equal in length, ideally with side 1 slightly longer than side 2.

MASTERING FROM DAT



As mentioned earlier, tapes should be fully edited before being presented for cutting, and this is particularly important in the case of digital tapes. Vinyl records are cut as one continuous groove; once you've started out on a side you can't stop until you get to the end! At CTS Mastering, the vast majority of work now arrives on DAT but there are still a number of very common basic problems in the tapes which present difficulties to disc cutting engineers, for example:

The gaps between the required tracks are not the correct duration.

The gaps between (or before) the required tracks are not silent (contain clicks, hiss, general unwanted sound).

The gaps between the tracks contain unformatted tape.

The required tracks are in the wrong order.

The required tracks are on completely different tapes.

Tracks are digitally compiled from source DATs employing different Sampling Frequencies (i.e. 44.1kHz or 48kHz) or Emphasis states. (This can cause the playback machine to produce momentary noise when it detects the change).

All these problems can be overcome by correctly editing the tracks together, either by using a digital editing system, or by carefully copying to analogue tape and then splicing in the conventional way. Digital editing need not be expensive, and analogue tape need not degrade the quality of the recording. Of course, if the material is also for release on CD, the problems can be solved by preparing the CD Tape Master first, then Cutting from that.

There are a few other 'do's and 'don't's that will help get a better result from DAT:

No music should be recorded on the first minute of the tape. The beginning of a tape is prone to a higher error rate and thus to a higher probability of drop-outs. It's OK for reference tones, however.

Recording levels should be set so that the highest peaks just reach between -3dB and -1dB.

You should always allow a couple of seconds to let the DAT machine settle down in record mode before you start a mix. This will ensure that the start of the music is not 'clipped'. For the same reason, also leave at least a couple of seconds after the end of the previous track when compiling.

Don't leave any unformatted (totally unrecorded) tape at the beginning of the tape or between tracks. If there is unwanted noise between two tracks, it is sometimes possible to 'fake' a quiet gap during cutting by the careful positioning of 'Skip' and 'Start' ID codes on the DAT recorder — the player will skip past the offending section and then immediately play the next track, but only if it is not confused by unformatted tape in the intervening section.

You should always check a DAT recording after you've made it, and double-check a recording before sending (or taking) it to a cut. While the music should be reproduced perfectly, drop-outs can be caused by a substandard section of tape, or by a speck of dirt momentarily passing the heads of the recorder.

It is always helpful if tones for channel identification and reference level are recorded at the beginning of a DAT. This should be accompanied by relevant information on the box or log sheet. Common practice is to record a 1kHz tone for about 30 seconds at the start of the tape, with the tone appearing on the left hand channel first, then equally on both. The reference level can be anywhere between 10 and 20dB below the peak level. -14dB is appropriate, as this equates quite closely to 0VU on the desk, but there is now a trend towards adopting -20dB as a digital reference level. Whatever reference level you choose, the tape box or log sheet should be labelled accordingly.

LABELLING



Many DAT cassettes are presented to cutting rooms with little or no information about the recordings on them and how they are to be cut. The following information should always be included on the cassette insert or an accompanying log sheet:

The client's name.

The artist's name.

The catalogue number (if known).

The format of the disc(s) to be cut, ie. 12745.

The title, duration, and start time (or ID number) of each track and side to be cut.

The running order of the disc(s) to be cut.

The sampling frequency and emphasis state of the recording.

Details of any line-up tones provided. (see above).

Any other details or comments which may be appropriate or helpful.

In addition to this, some kind of information should always be put on the body of the DAT cassette itself in case it becomes separated from its paperwork at any time.

DIGITAL EDITING



The cheapest way of editing a recording uses the good old-fashioned razor blade, but if you have made a digital recording you may feel that transferring it to analogue tape for editing is not an acceptable solution. If that is the case there are now a number of ways you can do the job digitally.

The most popular digital editing system in current use is Digidesign's Sound Tools. This is a software/hardware package which is available in versions for the Apple Macintosh and (less commonly) Atari ST computers. Sonic Solutions' SonicSystem is another Mac-based hard disk editor. The basic principal of this kind of editing is that the audio is first loaded into the computer and stored as a file or files on the hard disk. The software is then used to determine how the audio is played back — you could simply choose a running order and fine tune the gaps between tracks, or go in for some heavy-duty editing and remove clicks and pops, or chop out whole sections of tracks to change their length. The result is then recorded back onto tape afterwards. Some systems, such as SonicSystem, also offers facilities specifically designed with CD mastering in mind.

The AMS Audiofile was the original hard disk editing system, and it is still a useful tool, though one which is normally only used for more specific applications such as digital editing to picture for TV & film post-production.

You can also perform digital editing on tape rather than disk. Based on video editing systems, the Sony DAE 3000 tape editor (and its predecessor the DAE 1100) works by copy-compiling from one digital tape to another. In most cases this means that your recording must be on a PCM1630 3/4-inch U-matic tape before it can be edited, although the DAE 3000 can be modified to edit directly from the latest Sony PCM7000 series DAT machines.

CD MASTERING



A CD master is 'cut' from a CD Tape Master, a digital recording on U-matic tape with timecode and the subcode data that the CD format requires. This tape is in turn produced from a CD Master Tape, which is identical apart from the lack of subcode. This Master Tape can be compiled from any tape format.

If you are using DAT you should record at the 44.1 kHz sampling frequency as this will enable the recording to be transferred digitally without the use of additional analogue circuitry or sampling frequency convertors. Mastering rooms are in some cases now receiving DAT master tapes which have already been fully edited for CD. This will obviously save some time and expense in the production of the final CD tape master, but not, perhaps, as much as you would think. The reason is that if you edit without a 30 frames per second SMPTE timecode reference then all the index points (start and end times etc.) have to be located retrospectively, whereas if you edit using timecode these points can be located and marked as an integral part of the editing process. If the job involves a lot of music editing then you will probably win by doing your editing 'off-line', so to speak, but if the job is just simple compilation then you will almost certainly be better off giving the whole job to a CD Mastering Engineer. You should also bear in mind that if the gaps, fades, etc are not exactly as you want them then this will have to be attended to in mastering.

The final stage of CD Mastering is known as PQ coding. This process takes the timecode locations of all the index points and turns it into a digital data burst which is recorded at the start of the CD Tape Master. At this point the location of the index points must be confirmed to within one frame of timecode (a 30th of a second) otherwise the PQ code will be inaccurate, CD players will not locate or programme individual tracks correctly, and the CD will be deemed to be faulty!

At present it is only possible for CD plants to manufacture from PQ-coded NTSC U-matic masters from Sony PCM 1610 or 1630 systems. It is not yet possible to manufacture directly from DAT, even if your DAT has timecode or Absolute Time. It is possible that this situation may change in the future as timecoded DAT becomes more of a standard than it is at present.

CASSETTES



At the time of writing the good old cassette is still the most popular format in terms of album sales, and with the continued demise of vinyl, cassette singles have become more popular. If you are having tapes duplicated, do not send an original master tape to a cassette plant, but send them a copy. Ideally this will be an EQ'd production master, usually a DAT clone of the CD Master Tape or DAT copy made at the time of disc cutting, as appropriate. Obviously if the cassette is to have a different running order make sure that the copy is made in that sequence. Always state the durations of each side on the cassette production master.

If your music has a wide dynamic range you should discuss with the mastering engineer the advisability of producing a cassette production master with a modified dynamic range. What suits CD and vinyl does not always suit cassette.

WHAT HAPPENS NEXT — MANUFACTURING



There are two ways to approach the business of getting your CDs/records/tapes manufactured. The first way is to simply hand your tape over to a 'broker' or a manufacturer who can arrange the whole process for you. Alternatively, you can go it alone and arrange all the individual steps yourself. If you do this you will need to consider all the individual elements that go into records and tapes for release, including artwork and the printing of sleeves and labels.

The first thing you will need to organise is a catalogue number. This number identifies all the component parts of the record all the way through manufacture and will also be used by distributors, wholesalers and retailers. The number has to be unique and should be registered with Gallup and MCPS. You should also apply for a barcode (many retailers will now accept only discs and tapes with barcodes).

Next you need camera-ready artwork for labels and sleeves. Always proof-read your artwork carefully and thoroughly! It is worth bearing in mind that if you have a barcode it should appear on the label of a vinyl record as well as the sleeve, and should be printed in black on a very pale background, preferably white. Labels for vinyl records must be printed by a specialist record label punter as the specifications for both paper and ink are very stringent (due to the heat and pressure that are part of the pressing process).

Sleeve printing is less specialised but once printed, sleeves have to be folded and glued and this is best done by a specialist sleeve printer. Always get proofs when having artwork printed, and if the printing involves several colours ask for a Cromalin proof to avoid having expensive printing plates made up which then turn out to be unsatisfactory. Remember that if you specify Pantone colours (which guarantee that, for example, the orange you've chosen for your band name is exactly the right orange) this will probably turn out to be more expensive.

THE COSTS



Prices vary for all stages and processes described above, and of course you should shop around, but make sure you know what you're getting for your money. As always the professionals are there to help you, not rip you off. Don't be afraid to ask their advice, particularly if you're not sure about the cheapest way of doing something.

You should be able to cut a 7-inch single for around £100, a 12-inch for about £125 and an album for under £200. Processing lacquers (which is what a cutting facility actually, physically cuts) to stampers (from which records are pressed) can cost between £40-60 per side. Disc labels cost about £100 per thousand. 7-inch pressings can cost around 25-35p each. 12-inch pressings from 40-60p each.

Glass mastering for CD from PQ encoded U-matic tape and camera-ready label film costs about £350. CD pressings cost between 85-95p each. Minimum quantities: usually 1,000 but some manufacturers may be prepared to produce runs of 500 at a higher unit-cost.

Cassette duplication involves first the production of a bin-master, a long loop of tape with both sides of the album recorded in the exact same format as the final tapes. The cost for bin-mastering will be about £40 per title. Once again the unit cost of duplication varies with quantity, but for a C-50 (up to 25 mins per side) you might expect to pay something like 45-55p for each cassette.

Sleeve, inlay and booklet printing costs vary enormously according to the number of colours, pages etc. and are beyond the scope of this brief guide but you'll find a fully comprehensive guide to printers, manufacturers, mastering rooms and many other music business facilities in the Kemps International Music Book.

Both Mike Brown and Martin Giles have worked for many years in the music industry, previously as recording engineers and now as Mastering Engineers at CTS studios in Wembley.

FURTHER READING

Kemps International Music Book (£25)
Kemps Publishing Group, (Contact Details).

The Compact Disc (£30) by Ken Pohlman
SOS Bookshop, (Contact Details).

CD MANUFACTURING

Producing CD masters is considerably more complex and hi-tech than the vinyl-age gouging out of grooves in a piece of soft lacquer. Actually, that's not entirely true, as CD masters can be produced by Direct Metal Mastering, in which a diamond-tipped piezoelectric cutting stylus digs away at a thin layer of copper on a glass disk. Most CD mastering, however, uses the photoresist method, which goes like this...

The 'cutting' machine uses a laser to expose a thin coating of photoresist carried by a 'blank' glass disc. The laser's intensity is modulated by the data stream from the CD Tape Master, as the disc spins at between 200 and 500rpm (the rotational speed of a CD varies in order to maintain a constant bit-rate of 4.3218MHz). When the photoresist is developed, pits are etched into the photoresist where the laser intensity was highest, and a fine coating of metal evaporated onto the photoresist layer. This master is then used to produce, via an electroforming process, several nickel mould matrices which stamp CDs from polycarbonate plastic.

Clean air is critical to the CD production process, as CD pits are among the smallest manmade structures (1-3µm in length, around a 50th the thickness of a human hair). The air in a CD mastering lathe is typically specified to be Class 100, meaning that there must be no more than 100 particles between 0.5 and 5µm in diameter per cubic foot of air per minute. That's clean!


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Hands On: Yamaha SPX90

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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 - Dec 1991

Donated by: Bert Jansch / Adam Jansch

Previous article in this issue:

> Hands On: Yamaha SPX90

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