Signal connections at the desk end

1. The multicore provides connection between the stage and the mixing desk, for both the microphones from the stage to the desk and signals back to the stage and amps from the desk. The multicore must be made from multiple twisted pair screened cables, which are insulated from each other. The twisted pair prevents magnetic interference when it is used with balanced line connectors. The screen prevents electrostatic interference, while the insulation between the twisted pair screened cables provide isolation between the channels .The multi core can also provide connection for comms and DMX between front of house and stage

2. Effects at the desk are often connected using unbalanced jack to jack leads. The cable used in these leads must be screened to prevent noise pick up. The use of unbalanced screened jack to jacks is only possible because of the short distance between the desk and the effects which the signals must cover (under 2 meters) and the fact that the aux send signal to the effects inputs and effects outputs to effects returns on the desk is at line level (1 volt).

3. Some more pro Desks and effects units provide balanced line connections. Where possible these should be used to improve the interference rejection .Twisted pair screened cables must be used in these cases and terminated in the appropriate connectors (xlr or 3 pole jack)

4. When inserts are used on mixing channels, groups or masters, the connections are usually made with an “insert cable”. This is usually made from a 3-pole ¼” jack plug connected to two 2 pole ¼” jack plugs. Connection is made by joining the two screens of the two cables at the 3 pole jack here the junction of screens is soldered to the body and the signal of one cable is soldered to the ring of the 3 pole jack and the remaining signal cable is soldered to the tip of the 3 pole jack

At the other end of each cable a 2 pole jack is soldered with the screen connected to the body and the signal connected to the tip

On some expensive desks the inserts in and out are mad using two balanced in and out connectors. Here an insert cable as shown above is not applicable and in this case two balances line cables are used, one for the insert out from the desks (send) to the effect input and one for the effects out to the desks insert return.

5. laptop computers at the desk are often connected using unbalanced 3 pole mini jack to ¼” 2 pole jack leads. The cable used in these leads must be screened to prevent noise pick up. The use of this unbalanced screened mini jack to jacks is only possible where there is a short distance between the desk and the laptop (under 2 meters). If the signal has to travel further, Di Boxes with balanced line mike cables to a mike inputs must be used. Where the laptop is using its mains power supply and noise interference results, Di Boxes with their ground lifts in their lift setting must be used, to prevent the interference. . This is usually made from a 3-pole mini jack plug connected to two ¼ inch 2 pole jack plugs. Connection is made by joining the two screens of the two cables at the 3 pole jack here the junction of screens is soldered to the body and the signal of one cable is soldered to the ring of the 3 pole jack and the remaining signal cable is soldered to the tip of the 3 pole jack

At the other end of each cable a 2 pole jack is soldered with the screen connected to the body and the signal connected to the tip

Signal connections at the stage end

1. Only low impedance balanced output microphones and sources should be used to prevent interference pickup on the stage. Be careful to maintain the phase of signal sources usually +ve pin 2 and –ve pin 3 and that the screen is always on pin 1 .The signal connection between microphones and sources and the stage box must be made using a (balanced line screened cable) twisted pair screened cable, to reduce the pickup of both magnetic and electrostatic noise. These are usually terminated at the source end with a female xlr and the stage box end with a male xlr.

See appendix for diagrams

2. If unbalanced sound sources such as bass guitars, acoustic guitars, keyboards or computers must be connected; a direct injection box must be used. This provides impedance matching, balancing, ground isolation and level matching. The connection from the sound source and the Di box should be made using an un balanced screened signal cable while the connection from the Di box to the stage box made using a (balanced line screened cable) twisted pair screened cable.

3. The connection from the stage box returns to the amplifiers or speaker processors must be made with a (balanced line screened cable) twisted pair screened cable using suitable balanced connectors again. Again be careful to maintain the phase of signals +ve pin 2 and –ve pin 3 and that the screen is always on pin 1

4. The connection from the speaker processors to the amplifiers must be made with a (balanced line screened cable) twisted pair screened cable using suitable balanced connectors again. Again be careful to maintain the phase of signals +ve pin 2 and –ve pin 3 and that the screen is always on pin 1

See appendix for diagrams

5. Amplifier to loudspeaker connection must be made with suitably high cross section cable to prevent excessive volt drop along the cable .

The shorter the length of cable between amplifier and speaker the better. Two cores of cable must be used for each speaker. It is thought that multi-stranded conductor is preferable to solid conductors because it performs better at High Frequencies and in mobile applications is defiantly easier to handle when it must be rolled and unrolled continually. Where active pa systems are being used it is convenient to use 4 or 8 core speaker multi cores to reduce the number or runs. For instance in the case of a two way speaker system a 4 core speaker multi core can be used 2 cores for the bass The three common types of connector used for speaker connection are
1. Bare terminal black and red screw type
2. Jack (two pole) low power up to 100 watts
3. Speacon
a. Two pole suitable for one circuit
b. Four pole suitable for up to two circuits
c. Eight pole suitable for up to 4 circuits

The two most common used at present are the two and four pole Speacon. The advantages of these are;
1. The large cross sectional conductor they can deal with (up to 4 sq mm) ,
2. The they have plate type connectors in screw terminals for the incoming cable,
3. They have finger safe terminals
4. They have locking devices to prevent them falling out

The only disadvantages are: –
1. The fact they can be disassembled without a tool making them an electrocution hazard
2. There is only a male plug and a female chassis socket, so extensions can only be made using two cables terminated with male plugs on both ends and a female to female adaptor which is available

NL4MMX Speakon loudspeaker connector 4 pole

To 4 poles: two-speaker circuit

Connection over view

1. The two pole jack plug is connected with the signal (+ve) to the tip and the ground (-ve) to the body (only one circuit)
2. The three pole jack plug in balanced use is connected with the signal (+ve) to the tip, the signal (-ve) to the ring and the ground to the body (only one circuit)
3. The three-pole jack plug in insert mode is connected with the signal send (out) (+ve) to the tip, the signal return (in) (+ve) to the ring and the ground to the body. Note there are some manufacturers who swap send and return
4. The two pole speacon plug is connected with the +ve signal to the 1 + and the -ve signal to the 1 – (only one circuit)
5. The four pole speacon plug
a. for passive full range speaker operation, here it is connected with the +ve signal to the 1 + terminal in the connector and the -ve signal to the 1 – terminal in the connector.
b. In a bi amped situation the bass component is usually connected to +ve bass signal via the 1 + terminal in the connector and the -ve bass signal via the 1 – terminal in the connector, while the High frequency component is connected to +ve High frequency signal via the 2 + terminal in the connector and the -ve High frequency signal via the 2 – terminal in the connector.
c. Where more current drive is required, for example with high power bass units, the 1 +ve and 2 +ve may be linked together in the cabinet and connected to the drivers +ve terminal, while the 1-ve and 2 -ve are linked together in the cabinet and connected to the drivers -ve terminal .Here the amplifier’s output connectors must be wired to suit and a 4 wire cable used to take advantage of this arrangement
d. With amplifiers being used in bridge mode; care must be taken, as some have a separate speacon just for bridge mode output, while in others you have to make up special leads (check with their manual)

Note The above is not definitive so check before use

Safety Notes this list is not definitive and is only a rough guide

Safety Notes on Positioning

1. All cabling must be treated with care, as it can be potentially lethal at worst, or the cause of spurious noises or inconvenience.

2. Poorly laid out cable can cause a trip hazard, or if trapped underneath equipment, staging or doors can be severed or striped of its insulation.

3. Ensure cables lay flat, do not cross gangways un protected and are taped down in areas where people are to tread.

4. Do not use cables which are not long enough to reach without stretching

Safety Notes on Mains power cable

1. Ensure the mains cable is of the correct rating with a suitably high current and voltage rating for the job it is intended to be used for. . If it is not Do not use it . If you are not sure Do not use it. IF you do not understand how to determine its’ suitability Do not use it.

2. Visually check the cable’s insulation is not damaged 

3. Visually check the cable’s connectors are not damaged 

4. If the cable is not protected by a fuse or other protection device in its plug , check the source of the power adequately protects the cable