INTO GEAR

Equipping A Home Studio: Part 4

Published in SOS June 1998
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Technique : Recording/Mixing

EQUIPPING A HOME STUDIO

PART 4: Mastering is the final link in your sonic chain. DAVID MELLOR helps you make sure it's not the weak one...

The most important part of a recording is the fun and satisfaction you get from it. The second most important is the end product -- a tape or disc bearing your finished piece of music.

Mastering, in the recording studio, is the process whereby the final stereo output from the mixing console is recorded onto a stereo medium. This, as far as the recording studio is concerned, is the end product which you might take to a record company A&R executive to try and get a deal. If you already have a deal then the recording, or at least a copy, will be sent to a mastering studio where, applying the term in a slightly different sense, it will be mastered onto a Sony 1630 tape, Exabyte cartridge or PQ-coded recordable CD ready for CD manufacture. This is the last stage at which artistic decisions can be taken on matters such as equalisation, compression, editing and crossfading. After that, manufacturing is a purely technical procedure.

Alternatively, your recording might be mastered onto vinyl, which is still the consumer medium of choice in the dance music market. If you're really big, or really small, your recording could also be transferred onto a master for cassette duplication.

The final stereo master (in the studio sense of the term) is a very important thing, physically small as it may be. Mixing is an incredibly important part of the recording process, and the choice of medium that you mix onto merits very serious consideration. Let's survey the options...

This is the way everyone starts, through force of finances. On this topic I could observe that the technical quality of the cassette medium is so inferior that it shouldn't even be considered for mastering, and that there's no possibility that a master made on cassette could ever be acceptable for release on CD or vinyl, but although these are points you should bear in mind, it isn't necessarily that much of a drawback. If your music is any good, it will be good on whatever medium it is presented, and the fact is that CDs have been made from cassette masters. If the quality of the music is good enough, the listening public will generally accept minor technical imperfections. A lot can be done in a mastering suite to get the best out of a decently recorded cassette and the results can sometimes be surprising, even if some way off being ideal. As a final point on this subject I would say that although it is possible to master onto cassette (and if you have to, you should give your mix as much care and attention as your music deserves -- lots!), you really should be saving your money to move up to the professional bracket, so that your music can be presented at its absolute best.

Top professional engineers still master onto analogue open-reel tape, not because they are behind the times -- all the latest gear is available if they want it -- but because they like the sound. Analogue tape has a frequency response up to 25kHz or more if the recording equipment is well maintained. Many claim these extended high frequencies are audible and have an effect on the way we perceive music, even if audiometric tests show that they are beyond the range of most humans. Digital equipment, with very few exceptions, has a brick-wall filter at around 20kHz, so the high-frequency response ends there.

Even if the end product is to be a digital CD, some will say that it is better to preserve as much high-frequency content as possible, until the last possible moment. Others couldn't care less about frequencies above 20kHz but simply like the sound quality that results from mastering onto an analogue medium -- particularly if the multitrack recording was digital. There's another school of thought that detests the idea that music can be reduced to mere numbers [see our Digital Basics feature on page 204 of this issue for a description of how this happens], and they see the finished anal

"...you can still make a fully professional recording on an analogue recorder..."

ogue master as a one-off perfect end product, of which CDs are only imperfect imitations, like prints made from old master paintings.

Pro engineers will generally use half-inch stereo analogue recorders running at 30 inches per second (ips) -- twice the normal tape speed. This gives an excellent high-frequency response, sweet and clear, although some engineers continue to maintain that the bottom end sounds better at 15ips. Few would have a half-inch machine in their home studio but would be more likely to choose to mix in a commercial studio that had one, so perhaps they are a little beyond the scope of this series, but they're still worth knowing about.

Quarter-inch analogue recorders with a maximum tape speed of 15ips are much more common, and are available very cheaply on the second-hand market. I would say you'd have to be crazy to buy one new, but if no-one does, the manufacturers will go out of business and they will never be made any more! Quarter-inch machines don't really have the aura of their half-inch relatives, but there are reasons why you might choose to use one as your mastering machine rather than one of the digital alternatives:

• Analogue tape has a softer sound, and gently compresses harsh peaks.
• Editing with a razor blade and splicing tape may seem primitive, but it's still a lot cheaper than digital editing. (ADAT tape can't be edited without additional equipment).
• Your master is a 'living, breathing analogue recording' and not 'just a list of numbers'.
• You already have an analogue machine and don't want to spend any more money!

Although there are very many factors that would lead you to go the digital route and avoid analogue, you can still make a fully professional recording on an analogue recorder, so it's still a viable option. If you're buying second hand, there's no reason to accept anything less than a machine in excellent condition -- there are so many being offered for sale at the moment. Look at the heads: when they're new they have gently curving surfaces. If there are flat spots much more than 4mm wide, this is a sign that the heads will probably need replacing soon. Allow funds in your budget to have the machine aligned by an expert (several advertise in the back pages of SOS).

The great thing about DAT, besides the fact that it has the same sound quality as a CD, is that there are DAT machines everywhere on the planet. You should always be able to play your archive of DAT tapes, even after the format passes into manufacturing history, as long as they remain in good condition. Likewise, if an opportunity to release product into the Chilean market arises, they have DAT machines there, as well as in China, Hawaii, Alaska, the South Island of New Zealand and just about everywhere else you can post a padded envelope to. A DAT machine really is obligatory in just about every studio, since even if you prefer to master to another format, people will bring DAT tapes to you with samples, mixes and miscellaneous bits of audio they want to work with. It's also convenient to give your collaborators or customers DAT tapes of work in progress for them to listen to at home -- although some commercial studio owners are careful about who they give DAT copies to before the session has been paid for; you wouldn't want to master from a cassette, but there are no problems mastering from DAT!

There are a number of factors to consider when choosing a DAT recorder. Firstly, it's now fairly well known that a DAT tape recorded on one machine will sometimes not play properly on another, almost always because of faulty alignment of one of the machines. Obviously, the more you pay for a machine, the more likely it is to be set up properly, and it's also true that the more expensive machines, particularly those that feature varispeed capability, are more tolerant of tapes that are slightly iffy than cheaper machines that require things to be just so. The answer is to buy from a reputable dealer who regards DAT machines as bread-and-butter income; they're more likely to help you with any problems you come across, and they're likely to have inside knowledge on which machines visit the service bench most often.

The features of DAT machines tend to be very similar between makes and models. Here's a short list you should consider:

• Digital inputs and outputs: S/PDIF phono connectors are more common than optical, and therefore more useful.
• The ability to record at 44.1kHz sampling rate as well as 48kHz: CDs are always recorded at 44.1kHz, and it's better to record at this frequency to avoid the need for conversion.
• Lack of SCMS copy protection: SCMS doesn't protect you; it doesn't protect anybody -- it just prevents rightful copyright owners making digital copies of their own work. If a machine does feature SCMS, make sure that it can be switched off (and leave it switched off!).

You should also consider factors such as ease-of-use and robustness, and possibly portability. Sound quality tends not to be such an issue with DAT, and in fact with most digital equipment. If you can hear differences between different DAT machines, they are very, very small, and won't make the slightest difference to the marketability of your product. There have, in the past, been certain models with noisy A-D convertors, necessitating the application of pre-emphasis, which is an option in the fundamental DAT specification. Pre-emphasis boosts high frequencies on record, then de-emphasis cuts them back on replay, and in doing so cuts back high-frequency noise too. All DAT machines, as far as I know, can play back a pre-emphasised tape correctly, but hard disk editing systems may not recognise and correct the high-frequency boost, which is a problem.

Some DAT machines have features such as 'Super Bit Mapping', where the dither noise introduced into the signal as a necessary stage in the digital recording process is subtly manipulated to give better than the theoretical 16-bit performance. This is good for a first-generation recording or clone copy, but if the data is modified in any way, as it almost certainly will be somewhere along the line, the benefits are lost.

There is a school of thought that suggests that DAT is on the way out and recordable CD is the new trend in mastering. There are pros and cons either way, but recordable CD, or CD-R, is certainly well worth considering, though it is, I think, possible to be seduced by the 'pro' aura of CD.

It's the dream of many musicians to get their music onto CD, and CD-R is one way of doing it. There are two strands to recordable CDs: one is the stand-alone CD recorder which looks similar to a DAT machine. Those who like traditional equipment will feel well at home with this. The other is the computer peripheral CD-ROM writer which, with the appropriate software, can be used to generate audio CDs. I'll look at CD recorders first and save CD writers for after I've considered mastering to hard disk.

The fact that a CD recorder can produce a very high-quality master is not in dispute. Any disadvantages of CD recorders stem from the fact that CD was never intended to be a recordable medium: it was designed to be manufactured in quantity in a factory on heavy-duty presses. The CD-R medium is different from a standard CD in that it has a sensitive coating which can be written to by a laser, to produce a pattern of dots which look to any CD player just like the pits in the aluminium layer of a conventional CD. The problem area is that the CD standard calls for each CD to have a table of contents which describes to the player the tracks on the disc and where they are to be found. The table of contents, or TOC, fairly obviously can't be finalised until all the tracks have been copied, and therefore a CD-R can't be played on a conventional CD player until the disc has been 'fixed up' or 'finalised' and the TOC written. Up to that point additional tracks can be added, but afterwards no more tracks can be added even if only a few minutes of audio have been recorded. CD recorders can, of course, play partially recorded discs before the TOC has been generated.

Although a CD recorder may seem like a very attractive option, there are further drawbacks. Firstly, unless you have other equipment with which you can edit your audio, your finished stereo CD masters will be untidy round the edges, even though the main content will be OK. For instance, when you're recording using microphones, every track will be prefaced by noise, hum, clicks, breaths, chat, count-in -- all sounds that you wouldn't want your listening public to hear. If you're going to take your work to a mastering studio this isn't a problem, just an irritation (which, it must be said, also applies to DAT). Also, it's common when mixing that, even after many rehearsals, several attempts at recording are necessary to get level changes and fades right. Since a standard CD-R blank can't be erased, all of these failed attempts will be stored for posterity. Again, it isn't a problem if you're goin

"The most important part of a recording is the fun and satisfaction you get from it."

g onto a mastering studio, and have kept a note of which was the best version of the mix. Another point to bear in mind is that if you add tracks to a CD one at a time, the fact that the recording laser is switched on and off during the course of the disc means that you might hear clicks when the disc is played back on a normal CD player. It really is best to compile all the tracks on another medium and then copy them onto CD. This is the best way to optimise the performance and minimise the drawbacks of a CD recorder.

There are some CD recorders available now at comparatively low prices. Bear in mind, though, that the lower cost recorders demand that special audio CD blanks are used. and these are rather more expensive than standard CD-R media.

Another option is the CD-RW, or rewritable CD recorder. If you make a mistake in your mix, you simply erase it and have another go! You might imagine that any track on a disc can be erased at any time, but this is not the case. You can only erase the most recently recorded tracks, starting from the last track and working back towards the beginning. This is no different to DAT, where, although you can erase earlier tracks, hardly anyone ever does. It would be really nice if you could make up a compilation on a rewritable CD and then put it in your normal CD player so that you can make a copy, or copies, on the very much cheaper CD-R discs but, unfortunately, standard CD players don't currently recognise CD-RW discs, even after they are finalised.

It's a little-known fact that it is not only possible to master to ADAT [see our feature on this very subject in SOS February 1995], but there are also good reasons why it's desirable to do so. I have to say that I'm thinking about people who have multiple ADAT machines (or Tascam DTRS-format machines) who usually have tracks to spare. If you only have eight tracks, you'll probably use them all in multitracking.

The advantages of mixing onto the same tape as you used for multitracking are these:

• You only have one set of transport buttons to think about.
• You never have to worry about recording onto the wrong part of the stereo tape and erasing something else that you want to keep.
• You can mix in sections.

Mixing in sections is a very useful technique which gives a lot of the advantages of automation without the expense. A simple example would be where the verses and the choruses of a song need different fader levels for certain instruments. Often more changes are necessary than can be performed in real time with one pair of hands. With an ADAT, you can mix all the verses and then go back and punch in the choruses. (After you've done the verses it's a good plan to make a clone copy of the tape, in case you make a mistake on the punch-ins.) ADATs punch in beautifully, and nearly always absolutely seamlessly, with four selectable crossfade times -- better than hardware hard disk recorders that only give one fixed crossfade time, virtually a butt edit.

Another advantage of ADATs (not DTRS this time) is that 20-bit ADAT machines are now available at very attractive prices. So if you mix onto ADAT your master has, in theory, a signal-to-noise ratio which is 24dB better than DAT or CD. In practice the advantage will be a little less, but still worth having. The tricky bit will be transferring this onto CD in the digital domain; it's early days to recommend a reliable solution that will definitely work and allow the best possible 16-bit copy to be made, but at least you know that your master is future-proof.

Hard disk mastering is a tempting option for many. If you have a computer and multitrack audio recording software it's usually possible to mix into stereo completely within the computer. The procedure would be to get your recording sounding as good as possible with levels, EQ and effects (possibly automated) and then select the function commonly known as 'create file' or 'bounce'. This can be used to make a mono or stereo mix of the track as you've just heard it, but faster than real time, so you don't actually have to play the track through. Another point worth a mention is that there is also software available for mastering onto disk without multitrack recording or CD-writing facilities.

The advantages of mastering directly onto hard disk are several, besides its cost effectiveness. Firstly, you can do further work on your stereo master, such as editing, EQ and compression, assuming that your software has these capabilities. Secondly, when you have several mixes on disk you can sequence them and see what they would sound like as an album. You will almost certainly find subjective level discrepancies between tracks, even if you've taken care to make them all peak at the same level. There may be clashes between the EQ balance of adjacent tracks which need evening out. In the worst case, the vocal on one track may be very much louder than the vocal on the next, making them both seem incorrect. Compare this with having all your mixes scattered over several DAT tapes. Without at the very least having another DAT machine to compile onto, how can you know that your album is going to hang together properly?

The disadvantage of mastering onto disk is that the end product is not always portable from one system to another. What you should aim for is a mix in a standard format, created as a continuous file without edits. On the Macintosh, AIFF and Sound Designer II are the most common formats, and if you can transfer to a Zip or Jaz cartridge you'll find a reasonably large community of people with the right equipment to import and play your files. On the PC, the WAV format is ubiquitous and similarly portable. Whether AIFF, Sound Designer II or WAV, you should mix to a stereo file rather than the linked mono files that are sometimes possible. Stereo files are more commonly used for mastering and can always be split later on if need be.

CD Writer is the term generally given to a CD-recording device attached to a computer and normally used for making CD-ROMs. However, with the correct type of writer and the right software you can just as easily make audio CDs, on standard CD-R media (not the special audio kind) and sometimes CD-RW. Choosing a CD writer isn't all that easy, since they're often sold under brand names that conceal the true manufacturer of the CD-writing mechanism inside. One essential feature you will need is 'disc at once' recording, which means that the whole disc can be recorded in a single pass. If disc at once recording is not supported then the disc will be written 'track at once', which means that the laser writes a run-out section after each track. If the disc is to be a CD-ROM this is of little consequence, but on an audio CD it could result in clicks on playback.

Another feature you should look at in a CD writer is its speed. CD writers commonly come in 2x and 4x writing speed which means that a 74-minute disc (the maximum duration) can be written in 37 minutes or 18.5 minutes respectively (plus a little 'housekeeping' overhead). Reading speed is obviously not relevant unless you wish to use the CD writer as a conventional CD-ROM too. CD rewriters are also available which take advantage of the CD-RW media.

To use a CD writer you must already have audio recording software that will generate an AIFF, Sound Designer II or WAV file. In addition you'll need CD-writing software. You may find that when you buy your CD writer it comes with such software included in the price. Although this software will probably offer basic audio CD-writing functions, you'd be much better off with specialised audio CD-writing software that will allow you to set any length of pause between tracks, track levels, crossfades, copy protect, pre-emphasis and ISRC codes. In fact, you should aim to be able to make a fully Red Book-compliant CD (see SOS January '98 for info on the various CD standards), which can be sent directly to a CD manufacturer, bypassing the mastering studio.

The last option that I will mention briefly mastering to Minidisc. The sound quality of Minidisc isn't perfect but most people would say that it is certainly very good, and stereo Minidisc recorders can be bought at a very much lower cost than DAT or CD recorders, which makes them a practical option for many. They also have basic editing facilities that allow compilation of tracks, but not really editing within a track.

So that's it for Into Gear. I have been impressed by two things during my research. Firstly, there's such an immense amount of gear available, compared with when I first started writing for Sound On Sound. We're so lucky, but we still want more! Secondly, I can finish an article at the last possible moment before the deadline, email it to the editorial office where it is put into the issue which will be rushed onto the news stand in a matter of days -- and what I write is still out of date already by the time you read it! Such is the pace of change in sound and music technology. It's a little bit frightening, but don't forget that if you choose your equipment wisely now, whatever changes occur over the next year or two, your equipment will still be delivering the goods. You won't need to trade it in and update, but you can add to it whatever is latest and best. Recording may be an expensive hobby, but it's value for money in terms of the fun that you can get from it. And who knows, your first hit may be just around the corner and you can start planning a bigger and better studio all over again!