In the opening part of this series, we looked at a sound mixer in great detail; here in part two we shall place the mixer in the centre of a hardwired studio system that is typical of many small studios and home set-ups. We have seen how the audio signal travels through a typical mixer's inputs and outputs. Now we shall look more closely at the use of these various ins and outs, the equipment that may possibly be connected to them and the type of cables and plugs needed to do the job.

Hardwired

When talking about signals, studios can be simply divided into two types, hardwired and patching. Within this article we shall deal with the hardwired studio type. 'Patching' obviously refers to a studio that patches its equipment together which may cover all or part of the studio equipment, however, a hardwired studio is one where each piece of equipment is directly wired to another. Both systems have disadvantages and advantages but overall the patching system will offer the greatest creative flexibility, though the hardwired system is far simpler to use and is particularly suited to small home studios and Audio-Visual production.

Figure 1 illustrates the various pieces of equipment that you may connect to a typical mixer.

Multitrack Recorders (1)

Possibly the most important pieces of equipment connected to the mixer are the tape recorders. If you refer to the mixer diagram in the first part of 'Studio Anatomy' you will see that there are two options regarding the connection of the tape recorder playback: namely, via the normal Line input or the Remix input. Mixers differ in design so its worth consulting your particular handbook at this point, however, in general if you only have a line input then obviously you have no choice and that's the one to go for. If you have a Remix input then this is where a quick look at the mixer's manual will help you make a decision.

The Remix input illustrated in the Mixer Output Section diagram (June HSR) shows the Remix input routed to the monitoring section of the mixer. By plugging your tape recorder outputs into these sockets you will be able to monitor the tracks you have recorded. However, in order to actually mix the separate tracks together and produce a master mix, this socket can't be used and you would have to unplug from these Remix inputs and re-plug into the Line inputs. The Remix inputs on some mixers will route your signals through the normal input channel, therefore you're immediately ready to mix the multitrack tape down into a stereo master.

Tape recorder inputs normally come from one of two sources; Group outputs or direct Channel outputs. The Group output would be used when several sounds are being summed together ie. several mics around a drum kit, and will normally have a meter of some sort which will allow you to check the signal level. The direct Channel output will take the sound present in that particular channel and feed it directly to the previously selected track on the multitrack tape recorder. In this situation, you will have to use the multitrack tape recorder's own meters to check the signal level.

Those people who own budget mixers often buy a meter bridge attachment to provide some sort of metering, but this is not always necessary, especially if your multitrack and stereo mastering tape recorders are both within an arms length of the mixer and you can easily see their meters.

Mastering (2)

The tape recorder used for mastering the final stereo mix is normally connected to the stereo tape output and stereo tape input sockets. If your mixer doesn't have a dedicated stereo tape output then use the group outputs, say groups 1 and 2. Whichever you choose, the signals should be wired to the stereo tape recorder inputs, from where it will be recorded. The output from the tape recorder would be plugged into the stereo return input, sometimes known as the 'B' Return input.

This type of system will allow you to mix down onto a stereo tape recorder and then by pressing the stereo tape select button (B Return) you will be able to hear the sound which has been recorded onto the stereo machine, assuming that you have switched the machine into the 'tape' replay mode. This method also allows you to check the quality of the recording as its being made, by flicking between the mix going out of the mixing desk, and the mix that's coming back off the mastering machine's playback head.

Levels

At this point it's worth mentioning the dreaded problem of recording levels. We have spoken about the problems of level matching in sound equipment before, but there is no harm in a quick refresher.

When you combine -10dB equipment with the standard line level 0dB equipment you may run into problems of signal level compatibility. HSR published a small project in the June 1984 issue which outlined the construction and use of a line level attenuator. If you use a mixer of the 0dB or +4dB output type you will need to attenuate the levels before they go into a (-10dB) multitrack tape recorder such as Fostex, Teac, Tascam etc.

Signal Input

Without considering any sound sources this whole article would be a waste of time, so let's look at this situation. When recording with a mixer sound comes from two sources - either the microphone inputs or line inputs. It's fairly obvious which inputs to use when a separate balanced XLR mic input is provided. However, when there is only one input socket this would seem to indicate that you have to use the one socket for both types of input level and in this case it would always be used as a line input or high impedance unbalanced microphone input.

Wall Boxes (3)

When you are wiring up a studio and you have decided where you would like your mixer to be sited and your decision puts it next to a wall, it may not be desirable or ideal to have to keep on pulling your mixer out from the wall in order to insert a mic or line input. This can lead to cables becoming strained and eventually breaking. In this situation a better solution is to buy, or build yourself, a wall box which is fitted with the type of sockets your mics or other equipment are wired up for. By placing this box in an easily accessible position somewhere in the room and wiring the other end to the mixer inputs, you will be able to plug in instruments and mics without disturbing the mixer's main wiring.

Signal Processors (4)

The number of effects and signal processors found in any single studio will vary from one to another, but one thing you can be sure of is that once you have them you'll probably want to use them all the time. Fundamental devices such as reverb and echo can be permanently plugged into the auxiliary send (echo send) section of the mixer and depending on the number of auxiliaries, it may be possible to hook up other effects like flangers. If you do run out of auxiliaries then you could resort to using the mixer foldback section.

One small problem which you may once again encounter when linking effects to your mixer is that of level matching. This problem rarely occurs with effects devices, though if the mixer is of the -10dB output type and the effects unit you are using has no input gain control you could be in trouble. If this happens you can only resort to buying a line matching amplifier to boost the signal up to the normal 0dB operating level.

Insert Points (5)

Other devices such as noise gates and compressors would normally be plugged into the channel insert points on the mixer. The reason for doing this is that a device like a noise gate is only going to be used to act upon one particular signal, say that of a snare drum. By connecting it to the insert point on the snare drum mic channel, you can dedicate the noise gate to that channel and still leave the auxiliaries free for further signal processing by other devices. A similar situation would be true for a compressor, where, for example, it could be used on a bass guitar.

If your mixer lacks insert points you won't have this sort of luxury but it doesn't mean you can't use such devices. Two other methods of use exist. Line level and unbalanced high impedance microphone signals can be plugged straight into the processing device and then out of the unit and into the mixer; you can also take the group outputs in and out of these devices prior to going into any tape recorders. The last suggestion would be true for sounds which have originated from balanced mics, as these would first of all have to go into the mixer to boost their levels before being routed through the group output.

Cables

All cables used to connect studio equipment should be screened cable, the only exception being loudspeaker cable. It is particularly important to ensure that your cables all have good screens and that the screen is continuously connected throughout the studio's wiring. If it isn't, noise and radio frequency breakthrough may contaminate your signals.

Many large professional studios install what is called a balanced line system, which keeps electrical noise pick-up down to a minimum and other than building the whole studio inside a metal box it provides the most economic solution to electrical noise problems. However, most semi-pro studio equipment isn't designed for balanced line operation so you will have to take particular care over your screening.

Cables should always be of the best quality and where possible the screen should be woven rather than lapped. In permanent installations, all common cables should be laced together for neatness and labelled for easy identification. Connecting plugs, whether phonos, jacks or XLR, should all be of good quality and in order to retain a good screen they should be of the all-metal type, with no plastic outer cases.

When cables are going to be permanently plugged into equipment and rarely removed, such as the connections to tape recorders, you could use the cheaper metal plugs, but with cables that are being plugged in and out quite often, you should use the best plugs you can afford and make sure that they have good provision for gripping the cable. This type of plug will last longer than others but only if they have been correctly wired up. For details on the wiring of all the popular plug connectors, see the series Interconnect in previous issues of HSR.

Loudspeaker connections normally utilise heavy duty two-core cable: the QED type if you read Hi-Fi magazines, or just standard three-core mains cable of six amps or more rating if you're not worried about impressing your friends! You should not use thin bell wire so often passed off in those so-called High Street audio shops.

Colour

If you are wiring up a studio properly, its worth considering using coloured cables for the different types of signals. The following is an example of different coloured cables which are readily available from electronics shops. All line level signals could be one colour eg. grey; microphone cables could be black and loudspeaker cables orange or white. If you can afford it you could buy a variety of different coloured mic cables which will save yourself valuable time in the studio when trying to trace a faulty cable. Once upon a time coloured cables were almost unobtainable on the open market and would change hands for high prices, today the world is a better place and you can buy around ten different colours of cable all in a variety of widths and lengths from almost any decent shop that sells recording equipment.