This month, Paul White takes us over to the Master section of our hypothetical mixing console and discovers the reasoning behind some of its less obvious functions.

While the input channels of a mixing console at least benefit from being the same, the Master section of a console is actually a collection of different functions and facilities, which can make it difficult to understand, especially for those who haven't used multitrack mixers before. Even so, it can be broken down into logical groups which, in isolation, are all pretty straightforward in concept.

Whether a console has In-Line or Split monitoring has a great bearing on the complexity of the Master section; in a Split console, the monitor level, pan and aux controls are usually located above the Group faders, often in two rows. This takes up quite a lot of space and can result in the Master section being both large and cramped. Furthermore, useful extras such as several sets of stereo aux returns may have to be sacrificed in order to conserve space. Because of the need to be compact and to provide the maximum number of inputs at mixdown, the vast majority of new consoles aimed at the private recording market use In-Line monitoring, which is presented as a part of the channel strip, as described last month. Regardless of the type of console, the Sub-Grouping and routing arrangements tend to follow very similar lines.

Groups

On an 8-buss console, which is what last month's description was based upon, the Master section will include eight Group faders which serve to control the level of the signals being sent to the multitrack tape machine via the Group Output sockets. Like the channels, the Groups may be fitted with PFL and Mute buttons, and the metering section of the desk should include eight Group meters. Sometimes these meters may be switched so that they can monitor either the Group output or the multitrack tape returns, but because of the sophisticated monitoring arrangements provided by modern multitrack recorders, it is often adequate simply to monitor the multitrack outputs (console tape returns) at all times. For this reason, some budget consoles dispense with the switching and both the meters and the monitor section are permanently connected to the console's multitrack tape returns.

Because it is often desirable to be able to process a Group signal (or a Sub-Group when mixing), the Group outputs are invariably fitted with insert points allowing such devices as compressors, equalisers and enhancers to be connected.

Once the tracks of the multitrack tape have been filled up and it is time to mix, the channel routing buttons and Group faders may be used to create Sub-Groups of logical groups of instruments or voices, but we need some way of feeding these Sub-Groups into the stereo mix. The most common method is to use a button called 'Groups to L/R', or something similar, which routes the signal from the Group fader into the main stereo mix. The usual protocol is to route all odd-numbered Groups to the left of the stereo mix and all even-numbered Groups to the right. That way, if you want to create a stereo subgroup, the channels concerned may be routed to Groups 1,2 / 3,4 / 5,6 or 7,8 and then the channel Pan pot used to move the channel signal to the desired left/right position. The Sub-Group level will then be controlled by an adjacent pair of Group faders.

More elaborate consoles may have individual pan pots for each of the Group faders, which offers a little more flexibility in that it allows mono Sub-Groups to be created and then panned to any position in the stereo mix.

Aux Sends And Returns

Each Aux buss will have a master level control located in the Master section. If pre-fade Aux sends are being used to set up a cue mix, then the Aux Master provides overall level control of the cue mix. Similarly, if a post-fade send is being used to feed an effects unit, the Aux Master will set the level being fed to the effects unit. In effect, this performs the same job as the input level control on the effects unit.

As stated in the second part of this series (February '93 issue) the Aux Returns are really no more than simplified input channels; on a very simple multitrack console they may be routed directly to the stereo mix, but on most models, they have the same routing arrangements as the input channels. The main difference between the Aux Return and a main input channel is that there's no mic input and the EQ is likely to be simplified to a simple High/Low system. The Aux Returns may well have one or two Aux Send controls of their own, allowing effects to be fed into the cue mix without necessarily being recorded to tape. This is very important, as most singers perform better with a generous helping of reverb in their cans!

Because of the number of effects units with stereo outputs, it is not uncommon to find that some or even all of the returns on a modern mixer are stereo.

"Whether a console has in-line or split monitoring has a great bearing on the complexity of the Master section."

Master Faders

The main faders control the level of the stereo signal which is ultimately fed to the stereo mastering recorder. Under normal circumstances, the left and right faders should be set to the same position, and as a consequence, some desks opt to use a single, stereo fader instead. This has the advantage that manual fades are always even, but it does prevent the master faders from being used to balance up a mix that is slightly left or right heavy. Associated with the stereo faders are the stereo meters, which show the signal level at the main stereo output. These are invariably arranged so that they switch to showing true PFL/AFL signal levels when a PFL or AFL button is used.

The stereo output should also be fitted with insert points, and these are connected before the stereo faders. This allows whole mixes to be processed, for example, by compressors, enhancers or single-ended noise reduction units. It is important that these are connected before the faders, otherwise their operation would be affected during fade-outs.

Talkback

In a studio where the artists are in one room and the recording equipment in another, there has to be some way for the engineer to communicate with the artists. That's where the console Talkback system comes in, as it allows the engineer's mic to be routed into the Cue mix feeding the performers' headphones. The current trend is to have a small mic capsule built into the console to save having to connect an external mic, and — very importantly — the Talkback button is invariably non-latching so that you can't leave it on by mistake when you're making rude comments about the drummer! It is normal for the Talkback button to mute or attenuate the control room monitoring system so that the engineer doesn't have to shout over the mix.

The Talkback mic may also have a facility allowing it to be routed to the Group outputs. This is known as Slate mode and is a simple way of putting information such as song titles on all tracks of the multitrack tape before recording commences.

Oscillator

Test oscillators come in various formats, from a single tone to a full set of calibration tones for analogue multitrack alignment. Few budget desks offer a (minimum) full set of 100Hz, 1kHz and 10kHz tones, but most have the facility to provide a 1 kHz tone which can be routed to the Group and main outputs. Even a basic tone is a useful way of checking that all your Groups are getting as far as the multitrack tape machine, and recording a 0VU level tone on all tracks and then playing it back gives a rough and ready indication that the recorder is working. A long burst of 1 kHz tone at a prescribed level is also used at the start of master recordings to enable the cutting house or duplication plant to optimise their recording level.

Test tones are also useful for tracking down any breaks in a signal chain, typical examples being dirty patchbay jacks or dodgy console insert points.

Control Room Monitoring

Under normal circumstances, the control room monitor speakers will be fed from the stereo mix buss of the console; during recording, this will carry the monitor mix and when mixing, it will carry the final stereo mix made up of Input Channel signals (now fed from the multitrack outputs), Aux Returns and the Monitor channels (now free for use as additional line inputs). However, once the stereo mix has been committed to tape, you need to be able to play that tape back without repatching everything, which is why there's a 2-Track select button which switches the monitoring to the output of the master stereo recorder. More advanced desks may even offer a choice of two 2-Track machines, allowing you to switch between, for example, open reel and DAT master recorders. But there are occasions when it would be nice to check out other signal paths, such as individual Aux Sends, so some of the larger consoles include buttons which can select these signals to be heard in isolation over the monitoring system. This is particularly useful when you want to know what the cue mix which the musicians are getting sounds like — though to be fair, if you have a desk fitted with AFL and PFL buttons in all the right places, you can check most things. Regardless of what is selected on the console's control room monitor output, the main stereo output should always carry the stereo mix buss signal and shouldn't be affected if PFL or AFL buttons are operated. There's usually a level control for the PFL signal somewhere in the master section, as well as a master PFL/AFL LED that shows if one or more PFL/AFL buttons have been left on.

A level control in the form of a rotary pot is used to set the control room monitoring level, and this may be accompanied by a Dim switch which reduces the level when pushed, allowing questions to be answered or phone calls taken without having to change the monitor level control setting. Most mixers are fitted with a simple headphone output which provides a copy of the control room monitor signal and has its own level control.