UNIT 65:TECHNICAL STAGE OPERATIONS

By Joe Miri

SOUND

Sound source(CD player, microphone, iPod, etc…)

Sound desk Amp(Only needed if using passive speakers)

Speakers:(active or passive)

Speakers:(active or passive)

Basic diagram of how a P.A. system works

Sound Source

A sound source is anything that can be plugged into the sound desk that produces the sound that eventually comes out of the speakers.This includes: microphones, CD players, iPods, Phones and laptops.

Sound desk

The sound desk is used to control the level of sound coming into it from the sound source and how it sounds coming out of the speakers. That can be by changing the frequency or just changing

the volume. It can also pan the sound to different speakers if its using a stereo (stereo means that the sound can be split to left and right speakers) sound source; this is usually a CD player, laptop or iPod.

Microphones however can’t be stereo as they’re only a mono (mono means that the sound coming through can’t be split into different sections such as drums guitar and singing from a CD player) sound source but they can be sound source but they can be panned to certain speakers.

On the back or sometimes on the top of smaller sound desks you can find the channel inputs and sound desk outputs. On this particular desk they are all on the

back. You will also find the power input.On this desk there are 24 channels each with two ¼ inch jack input and one XLR input.

If you put two ¼ inch jacks into one channel from one sound source the sound would come out mono as the song would be split but because its all going into one channel it would just merge back together and come out of two speakers making the same sounds in each. To make it stereo you would need a cable splitting at the end into two ¼ inch jacks and you would put one in the first channels and one in a second channel to split the sound.

An XLR input would be used if plugging a mic straight into the desk.

This desk has three output:One is a mono output were the sound will come out merged together.The other two are stereo output that split the sound the sound of to right and left speakers

Here is the desks power input and power button.

Controlling the deskThese are the knobs and faders used to

control the sound desk.Gain

E.Q

Channel volume fader

P.F.L

Channel on

button

Master volume

Peak monitor

Pan

Reverb & Delay

AUX

Gain – is the white knob that sets the threshold for how much sound can come into the desk from the sound sourcePeak monitor – this shows you how much sound is going into the desk when using gain and the channel is on with PFL. Green is good and this should be the ideal level to keep the sound at on the desk otherwise the sound may sound distorted. It’s okay for it to flicker into orange a little but red is BAD and the sound shouldn’t be hitting red on the peak monitor.P.F.L (pre fade listen) – this cuts out all other noise going to the peak monitor and allows you to control how much sound is coming through the channel via the gain button.Channel on button - this button turns the channel on allowing sound to go through it without pressing this button it won’t play sound through it and the PFL for that channel will also not work. On some desks it will be a mute button not an on button.

Channel volume fader – controls how loud the sound is coming out of the channel.Master volume – this is the main volume and is set to the number 0 on its fader so that you get a clear sound coming through the desk. If it isn’t up then the sound won’t play through the desk from any channel.Pan – the pan knob allows you to pick which speakers the sound will come from. For example if you had two speakers and you plugged one into the left stereo output and the other into the right you can pick which speaker the sound from each channel will come from, if you turn the pan knob fully to the right then all the sound will come from the speaker plugged into the right output and if you turn the pan fully to the left then all the sound will come from the speaker that’s plugged into the left output on the desk. If the pan is placed in the middle then the sound will come from both speakers.

E.Q (equalizer) – the EQ are four green knobs on the sound desk that are used to manipulate the sound to make it sound natural. The four knobs manipulate three sound frequencies one that controls high, two that control middle and one that controls low (sometimes called bass)• High – either boosts or cuts the high frequency • Medium top – selects the frequency • Medium bottom – boosts or cuts the chosen

frequency on the medium top.• Low – boosts or cuts the low/bass frequency.• To boost the frequency the knob must be

turned to the right and to cut the frequency the knob must be turned to the left.

This would be used during a sound test for a band to make sure the singers voice and instruments sound as they do in real life.

Reverb – controls how much the sound is echoed and gives nice acoustics to a sound.Delay – changes the amount of delay on a sound making it seem like a sound source is further away and making a venue seem larger.Aux (auxiliary) – this is used for added devices such as staged wedges to control the level of sound coming out of them.

Active speakersThese speakers have a built in amp meaning that an amp isn’t needed and therefore less equipment is needed to be transported, this would be help for a restaurant singer or a pub singer as it is less equipment they need to carry and bring with them and set up.On the back of the speaker there are dials to control the level of sound produced and how clear it is so from this the aim is to make it as clear as possible as it can be made louder from the desk.This needs to be pugged into a power source.

Passive speakersThese need the use of an external amp to work however as it doesn’t have a built in amp this makes it lighter and therefore better for rigging. This would be better for rigging in a theatre or a music venue as it’s light it is easier to lift up to the rig and also cause less strain on the rig as they’re lighter it also means that in the event of it coming off the rig it won’t be as heavy on the safety chain.This also needs plugging into a power source to. As it needs plugging into an amp it also need the use of speakon cable to connect the speaker to the amp.

Input Cables

XLR – this cable is used to connect the output of the desk to the input on the speakers and also it can be used to connect some microphones to inputs to.Jacks – jacks come in 2 sizes there is the ¼ inch jack and there is the mini jack. Mini jacks fit into phones and iPods. ¼ inch jacks fit into inputs on the desk and guitars. It is possible to get an adaptor.Phono lead – phono leads are used to attach such things as CD players or computers. For sound the colours of the inputs are usually red and black however some may have yellow to but that is for visually and is not needed for sound.Speakon – this is used to connect a passive speaker to an amp

Power Cables

Kettle lead – A kettle lead is used to power such things as the sound desk and the speakers.Figure 8 – A figure 8 lead is used to power such things as a CD player or a radio.