The Alice Soundtech Series A broadcast desk

This is often called the mixer, which is actually a bit of a misnomer since it is more of a selector. Its main function is to enable you to choose which of a variety of sources of sound you want to send to your listener.

It is divided into sections:

1. On the far left, the monitor and output section

2. On the right, stereo channels

3. In the middle, the phone and IRN channels

4. On the near left, mono microphone channels

Monitor and output section

The output section is dominated by two black meters. These normally show the output left and right but are also used for checking cue levels - more on this in a moment. The volume of the DJ headphones and also the loudspeakers is controlled by a couple of knobs which are coloured blue (upper knob - speaker, lower knob - headphones). You adjust these to suit yourself - they do not affect what is broadcast.

To monitor accurately it is essential to have a consistent volume in the speakers. Thus, when you start your shift/programme, set the speaker volume at a comfortable level and then leave it. If you need to reduce volume (eg when answering phone), use the 'dim' button so you don't lose your reference level.

Also on the output section are the oscillator, talkback controls, limiters, off-air button and the aux line output controls (for aux lines see later).


The desk is provided with a variable-frequency oscillator (tone generator). This is designed to assist technical staff in setting up levels, but is also useful if you want to set the record level when you aren't on air.

Turn on oscillator (button above the green 'osc' knob) and feed it to mixer output by pressing the uppermost of the four buttons just below osc knob. (Similarly, a tone can be fed to aux 1 or aux 2. Do not press 'mixer' button if on air.) Adjust the level of the tone now assaulting your ears till it shows 4 on the output meter. (The frequency of the oscillator can be varied by changing the positions of the two buttons just above the osc button.) Set input gain to read 0 on recording machine. Turn off oscillator.


Pressing this enables communication between studios using the little goose-neck mic. Incoming and outgoing volume of talkback depend on the settings of TB and RTB (‘talkback’ and ‘return talkback’) and incoming talkback will only be heard if RTB button is pressed.


These are safety devices to ensure the transmitters are not overloaded. However if the limiters do start cutting in (as shown by the LEDs flashing) then you are probably driving things too hard.

The two knobs controlling the limiters are usually fully clockwise, both 'enable' buttons are down and the 'link' button is down. Link is used so that whichever channel starts to limit the other will follow it, otherwise you would get stereo image shifting, admittedly not much of a problem in mono.

Off-air button

It is in fact taken from the feed to the transmitters, not 'off air'. It is used to check station output whilst changing over from desk to Xfm.

Individual channels

Since many of the functions are common to all channels, try simply looking at one channel and it will make the desk seem simpler.

Three little buttons at the top

On the stereo channels these are 'left', 'right' and 'RIAA'. For a normal stereo input both left and right buttons are up but if for any reason there is no input on one channel ('the signal has gone one-legged'), then push the button relevant to the channel that is still working in order to share that signal between both channels with no loss of level.

The third button selects between one of two possible inputs. On the gram channels it is labelled ‘line/RIAA’ but has only one function and should be left down. On other channels it selects line 1 or line 2.

What does RIAA mean? When being manufactured vinyl is cut with reduced bass to make sure the needle doesn’t jump out of the groove on loud bits! The bass is then boosted when the record is played. This boosting follows a special curve optimised by the Radio Institute Association of America (RIAA) and is used when feeding a record deck directly in to the desk.

On the microphone channels these three buttons have different functions. From the top:

  1. The pad reduces the input level, and is only normally used if the desk is used as a stage mixer, so we don't need it.
  2. Local/remote mutes the speakers when the microphone is used otherwise there is the possibility of feedback or 'ring- round' - not a nice noise. If our guests were in a separate studio we could listen to them on the speakers which gives better results for the person doing the mixing, but is not possible (yet).
  3. Mic/line enables each channel to choose between either the microphone assigned to that channel (colour-coded to reduce confusion) or a line input. When using a line input ensure the EQ section is switched out by using the EQ button below the lowest blue EQ knob.

Whenever a microphone, especially a capacitor mic, is used close up there is a danger of 'popping' on 'p' sounds. The filter button marked 80Hz is a 'high pass' (or low frequency) filter and helps prevent popping. It also reduces any motor noise that might be picked up through the mic stand. (The on button near the top of the fader is used if the desk is used as a stage mixer, in assocation with the 'peak' lamp just by it, to help kill feedback quickly and is left 'on'.)

In addition, on the stereo channels only, there is a button marked +14dB, just below the gain control. This boosts the input gain by three-quarters of a turn and can be helpful if your signal is otherwise unusable.


Equalisation/tone controls

All the desk channels have gain and fader; most other functions differ. The most obvious difference is the tone control or equalisation (EQ) section. No tone controls are fitted to line input channels. This is because line inputs are assumed to be fully equalised (tonally neutral) and pre-amplified to a level of 0dB. Microphone channels however are much more complicated partly because of the much lower output of a microphone which necessitates further amplification to reach 0dB; also tone controls are fitted.

A cardioid microphone (as used at Xpression), used at a distance of about 1 to 2 feet, only needs to be amplified to reach 0dB. However, when used closer, the behaviour varies. When used very close (less than 2 inches), it emphasises bass frequencies. Voices also vary and for clarity it may be better to slightly emphasise the higher frequencies.

If EQ is fitted, use it very sparingly, if at all. You may find, for example, you are pushing out ppm6 but if you take the bass away (which does not help clarity anyway) it may go down to 3, if you see what I mean. Most sound engineers rely on the mic itself to give them the result they seek and use minimal EQ. If you must, just a tiny bit of treble boost (to about 1 or 2 o’clock).

The human voice has a frequency range of about 300Hz to 3KHz. Beware of too much bass if male or treble if female. Bass can make you sound woolly; treble too thin and nasal.

Be especially wary of the centre two controls - the swept equaliser (variable frequency) section. This is mostly used when a mixer is used for PA; it is a means of tuning out feedback at a certain frequency, and can sound decidedly odd on radio if care isn't taken.

Pre-fade listen

Remembering that the fader will put whatever is on that channel out on air, leave the fader down. To prepare a channel for broadcast first press the relevant PFL button. This will mute whatever else was coming through your speakers and headphones and what you now hear is whatever is on your chosen channel, but in mono. The two meters to your left will also show your chosen channel, also in mono. Start your source of sound and check level (4½). Re-cue and release PFL.

When opening channel DO NOT bring fader to the top. STOP at the ‘0’ mark.

Cueing and remote starts

Cueing in radio terms is to set up an input so it is ready to start at your chosen point when you call for it - usually this call is by closing a switch. PFL is to check level before presenting signal to air. Whenever prefading, remember the fader stays down!

Remote start on gram channels is either via button or fader; CDs start via button plus fader. On CD channel, leaving ON button down will lock all CD controls – useful to prevent inadvertent eject etc of CD being played on air but may be confusing at first. No remote start on computer as yet.

Telephone channel (also used for the IRN news)

This looks similar to the others, but differs almost totally. Its function is twofold (threefold if you count its line input capability):

  1. It enables a person on the telephone to talk on the air.
  2. It gives the caller the output of the station while they are waiting, so they know what's happening.

In practice this is what happens. A telephone call is received and either you hear the ring outside or you may see the little lamp just above the main fader flash in sympathy with the ring. You answer the call, when possible, and if you choose to put the caller on the air you tell them to stand by. Press the third small button from the top - the one marked 'Tel/line' - to the up position. Doing this is the equivalent of answering the phone and transfers the caller from the telephone to the mixer and 'holds' the call. You may now hang up the phone.

Using the desk as a telephone

Depressing PFL now enables you to listen to your caller - who can't hear you; all they can hear is whatever the desk is putting out. In order to talk to them, press the second button from the top - COMM (short for communicate). This cuts off the feed and instead the caller will hear your microphone, allowing two-way communication so you can set their level. Note that COMM has no function of its own; it only works in conjunction with PFL. You don’t need to touch the DJ mic channel - this is all done automatically. At this point what you should say is, 'Stand by please. You'll hear the programme over the telephone handset. When I speak to you you'll be live on air.’ This cumbersome spiel is a legal requirement as laid down by the British Telecom code of practice for broadcasters, but on smaller stations is as common as the dodo. However never put anyone on air without their knowledge. Note that there is no profanity delay, so pre-record calls if you think there might be a need.

Take off COMM and PFL. The caller again hears 'desk output'. Introduce caller and bring up fader. Converse as desired; bring down fader. If you wish to talk further off air with your caller, either use PFL and COMM as before or pick up the phone and release the call by pushing phone/line. Either way at the end of the call be absolutely sure the phone/line button is back in the 'line' position. To be certain, lift the phone - you should hear the dialling tone. If you don't, no call can come in, and if you initiated the call the phone meter will go on clocking up. Professional stations have failed to check this and given themselves huge bills, and Xpression pays its own phone bill.

The tone knobs will not be needed for the phone, but the filter button at the top of the EQ section is useful. It is called a 'bell' filter because of the shape of its frequency; filters are normally 'shelving'. It is only for use with the phone (not IRN) and since its frequency response is the same as that of a phone line it can help clean up a noisy phone call (crackles and clicks etc). (This is dependent on obtaining a new ‘hybrid’ for this desk…watch this space!)


Aux lines

The Alice Soundtech desk is also usable as a stage mixer (a manufacturer's ploy since there is only a small market for broadcast desks). This means that certain features are not normally applicable to a radio studio, but one very useful feature is the aux line, which usually provides an on-stage mix.

Normally the only output is via the faders, fed (eventually) to the transmitter. There are also other outputs which are fed via two master levels controls, and may be either pre- or post- fade.

Aux 1, 'under the desk', can be used to feed alternative inputs on recording machines. Aux 2 has no function.

To use aux 1 to record from any channel (except telephone) while desk is being used 'on air', proceed as follows. (This feature is subject to availability)

Start the signal, turn up the aux 1 knob on that channel to approximately three-quarters full. Press the little button just below this knob - it is marked PRE and ensures that the output will not depend on the fader being up. (Make sure also that the PRE button on all other channels is off and all other aux knobs at a minimum.)

Now turn to the knob on the output section marked 'aux 1 send', having pressed the AFL (after-fade listen) button next to it, and turn it up till your desired level is reached - 4½ to 6 depending on type of material. Take off AFL as soon as possible to avoid annoying the on-air presenter.

Now record etc and when finished return all knobs/switches to zero/up