Wiring & Connectors
Faulty connectors and cabling are some of the most frequent sources of noise and poor sounding systems. The following section should help you connect your system correctly. It’s also worth spending a little time referring to all of your user manuals, as wiring conventions can vary between manufacturers - see diagrams.
Balanced and Unbalanced Mic Inputs
Soundcraft uses XLR sockets for its balanced mic inputs.
The wiring convention for XLRs is: Pin 1 - Shield, Pin 2 -Hot (+ve) and Pin 3 - Cold (–ve).
Balancing is a method of audio connection which cancels any interference in a signal, to give low noise operation. This is achieved by using a 2-conductor mic cable, usually surrounded by a shield, in which the ‘hot’ and ‘cold’ signals are opposite polarity. Any interference picked up will be of the same polarity on both hot and cold wires and will be rejected by the mic input’s Difference Amplifier. You may use unbalanced sources when wired as shown. However, do not use unbalanced sources with Phantom Power switched on. The voltage on Pins 2 & 3 of the XLR connector may cause serious damage.
Balanced and Unbalanced Line Inputs
Line inputs accept ‘A’ Gauge, 3-pole (Tip, Ring, Sleeve) 1/4 inch jack wired as shown in Fig. 7.3.
Note that for unbalanced operation the screen of the cable is wired to both the Ring and the Sleeve of the jack.
Inserts
A Mixer insert point is a single, ‘A’ Gauge, 3-pole (stereo), switched jack socket (not unlike the headphone socket on a hi-fi amplifier). When a 3-pole jack is inserted the signal path is interrupted. The signal is taken out of the mixer via the plug tip, through an external piece of equipment and then back to the mixer on the ring of the plug. A special Y-cord is required which has the stereo jack at one end and two mono jacks, for the processor’s input and output, at the other. See Fig. 7.4.