A device to convert from one type of connector to another.
The increase or decrease in the size of the signal. Often referred to as the Gain of a system.
The amount of reduction in the size of a signal. Measured in decibells (dB).
The frequency range that we hear. Often quoted as about 20Hz to 20kHz. But the highest frequencies we can hear decreases with age down to about 12kHz.
A signal carried by two conductors “+” and “-” each with an equal impedance relative to ground. In audio applications typically carried by a screened twisted pair cable.
A means of connecting one piece of equipment to another – see separate descriptions.
A heart shaped reception area showing the locations where a microphone will pick up signals.
A self contained amplifier and speaker housed in a single cabinet. Typically used by guitarists and keyboard players as their main source of sound if they don’t have access to a PA system. Alternatively they can be used in conjunction with a PA system as dedicated monitors for guitarists or keyboard players.
A high quality (powered) mic used for speech often with a much wider pickup range than a dynamic mic. It uses the change in capacitance to produce the output signal. A DC voltage needs to be applied to enable it to work. Power is either supplied via an internal battery within the mic case, or via phantom power.
The metal (copper) part of a cable; the part that actually carries the electric current.
The amount of electricity flow. Usually measure in Amps (A) or 1/1000ths of an amp: milli-amps (mA)
A unit of measurement. Can be referenced to specific audible volumes (dBA) or to electrical power (dBw) or voltage (dBV). Alternatively it can be a relative measurement of one quantity to another (dB). A change of +3dB means a doubling of the power. A change of –3dB means a halving in power. A change of 10db means increasing or decreasing the power by a factor of 10. The scale is linear so a change of 20dB means increasing or decreasing the power by a factor of 100.
D-I Box (Direct Injection Box)
A device that is used to connect an unbalanced signal, typically from an instrument via a jack plug, to a balanced cable connected via an XLR plug. They can be either active ie powered by a battery; or passive ie not powered. They are used for changing signal levels and for isolating equipment connected via mains plugs/sockets located a long way from one another eg a guitar amp and a mixing desk.
A mic used by vocalists that is intended to be used by a single person at close range. Use electromagnetic induction to produce the signal.
The variation between the smallest and largest signal levels that the system can operate over.
One phenomenon which causes unwanted 50Hz mains hum to be heard. It is often caused by connecting two pieces of equipment together, each of which is connected to the mains at different locations in the building. The remedy is to have just a single earth connection for the whole system or to isolate the two pieces of equipment via a DI Box.
EFX (Short for Effects)
These controls and connectors are normally used to feed effects units, things like reverberation units, gates, delays, and other pieces of kit that alter the sound of signals
Signals are fed from the desk into the effects unit and then back into the mixing desk. The level of signal going to the effects unit is controlled by the “EFX” control on the relevant channel. The overall level of the combined signal going to the effects unit is set by the “Effects Send” control. The level of signal feeding back into the mixer is controlled by the “Effects Return” control.
A device to alter the gain of different frequencies making up the signal. Tone controls in Hi-fi.
A volume control that is normally a linear slider control. Often they are calibrated in dBs. Pushing the slider away from you increases the volume; pulling the slider towards you reduces the volume. There is one fader per input channel, a pair for stereo F-o-H labelled “L & R” and one fader for each of the “Monitor” outputs.
A problem caused by microphones being placed to close to a speaker that is feeding out an amplified version of the microphone signal. Often heard as a high frequency scream or whistle.
Sometimes referred to as a socket. A connector that accepts the pins from a male connector.
A secondary PA system intended solely for the use of musicians so that they can hear themselves and other members of the band.
The pitch of a sound. Measured in Hertz (Hz) or KiloHertz (kHz) ie 1,000s of Hertz
The main source of sound intended to be heard by the audience / congregation. Salem’s Main system is 160watts per side. Salem’s gallery system is 40 watts per side.
The amount of amplification in a system. Usually measured in decibels (dBs). A 6dB increase = a doubling in voltage. A 3dB increase = a doubling in power.
A multi-channel device (typically 15 or 31 channels) that provides very accurate adjustment of narrow bands of frequencies to counteract the audio characteristics of the room. Once set the adjustments should not be altered. The Salem system has a 15 channel stereo graphic equaliser.
Groups (in Mixing Desk)
A means of combining several channels together before feeding them to front-of-house so that the level from all of the channels can all be controlled together by a single (Group) fader.
Headroom (in amplifiers)
The amount of spare capability above the operating level before the amplifier begins to go into overload.
Measurement of frequency – the number of cycles per second. 1 cycle per second = 1Hz
An extreme example of a cardioid heart shaped frequency response giving a very narrow, focussed, reception area.
A single loop of wire, invisible to the casual observer, that circles a specific area of the room. People sitting inside the loop can turn their hearing aids to the “T” position and listen to the signal fed from the mixing desk into the loop amplifier. This is useful on speech and recorded music but is much less useful on live music.
Input sensitivity control
This control determines how much signal from whatever source goes into the relevant mixer channel. The key point is to have just the right amount of signal so that the channel doesn’t distort (too much signal), or be subject to electronic noise (too little signal). The correct level is set using the PFL and LED indicators.
The non metal parts of a cable that separate the conductors. Often some form of synthetic plastic.
A type of audio connector – see section on cables and connectors
The size of the signal measured in volts (V) or milli-volts (mV). Often equates to “volume”.
Line level signal
A signal at an intermediate level of around 1v RMS
An amplifier specifically designed to accept a signal from the mixing desk a feed it into the induction loop. Typically they have a set of indicators to show that a signal is present.
Mains Hum (50Hz)
A low frequency “hum” caused by local mains operated equipment close by the audio equipment. It can be eliminated by correct earthing and use of balanced cables wherever possible.
Sometimes referred to as a plug. A connector that has pins that mate with a female connector.
Mixer (Mixing Desk)
A device which combines signals and sends the combined signal to other devices (typically a power amplifier).
Monitor (has two meanings)
- To check a signal either by eye (looking at a meter) or by ear (via a speaker or headphones).
- Fold-back speakers are often referred to as monitors.
A set of cables running from a stage box, located near the stage, to the mixing desk. Typically a single out sheath will contain 8, 16, 24, or 32 channels. In some case there are also four channels feeding signals from the mixing desk to the stage to feed power amplifiers and fold-back systems. Salem’s system has 9 individual channels feeding 3 boxes each terminated in 3 XLR connectors.
A push button switch that switches an input channel completely off or on.
The unit of measure of resistance.
A reception area that extends over the full 360 degrees of 3-dimensional space. Can be applied to microphones or radio aerials
A professional high quality audio connector manufactured by Neutrik.
Rotary controls on each channel that adjust the balance between the left and right F-o-H signals
PFL (Pre-Fade Listen)
A switch which feeds a single channel to the LED indicators and the headphone output.
A 48v DC voltage generated within the mixing desk and fed down the multi-core into condenser mic’s. In some desks phantom power is either fed to all the input channels or to none of them. On other mixing desks it’s possible to switch phantom power onto single input channels.
A guitar pickup that generates an electrical signal as the result of applied mechanical stress caused by the vibration of the body of the guitar. Typically located under the saddle of acoustic guitars.
The main amplifiers that provide most of the amplification in the system. They are fed from the mixing desk and feed into the main front-of-house speakers and into passive (non-powered) fold-back speakers if present. Salem’s fold-back units include their own power amplifiers.
The first stage of a multi-stage amplification system. Typically converting low level microphone or acoustic pickups to line level signals. May also incorporate some form of tone control or equalisation.
A woven or foil metal sheath that surrounds the insulated conductors in a cable. It’s normally connected to the earth of the system.
A very highly directional microphone often used to collect signals from a “point source” at some distance from the microphone.
A way of representing audio information electrically.
A professional quality dynamic PA mic. Manufactured by Shure. It’s the industry standard for mic’ing instruments.
A professional quality dynamic PA mic. Manufactured by Shure. It’s the industry standard for speech and vocalists.
A signal carried by two conductors one of which is at earth potential. Examples are coax cables with a single core and a screen.
The size of a signal typically measured in Volts(V); or 1/1000ths of a volt (milli-volts (mV)
The unit of measurement of power. In our context normally measured in milli-watts (mW), watts (W) or kilowatts (kW).
A type of audio connector – see section on cables and connectors
Written by David Smith and Updated by Rowan Burton
Copyright © The Production Works 2015