Mains Installation - SoundCraft LIVE 8 User Manual

MAINS INSTALLATION

General Wiring Procedures
To take full advantage of the excellent signal to noise ratio and low distortion of Soundcraft consoles, care must be taken to ensure that
incorrect installation and wiring does not degrade the performance of the desk. Hum, buzz, instability and Radio Frequency interference
can usually be traced to earth loops and inferior earthing systems. In some areas, especially heavily industrial areas, the incoming mains
earth will not be adequate and a separate technical earth for all the audio equipment must be supplied. However, check with your local
electricity supply company to ensure that safety regulations are not infringed or negated.
The successful, hum free, installation of a system requires forethought, and the establishment of a set of ground rules, which must be
consistently adhered to at all stages of installation.
Initial Wiring Considerations
For optimum performance, it is essential for the earthing system to be clean and noise free, as all signals are referenced
to this earth. A central point should be decided on for the main earth point system, and all earths should be 'star fed' from
this point. It is common electrical practice to `daisy chain' the earths to all electrical outlets but this method is unsuitable for
audio installations. The preferred method is to run an individual earth wire from each outlet, back to the system star point
to provide a safety earth screen reference for each piece of equipment.A separate earth wire should also be run from each equipment
rack and area, to the star point. This may or may not be used depending on circumstances, but it is easier to install in the first place, than
later when problems arise.The location of the star point should be a convenient, easily accessible place, preferably at the rear of the
console or in the main equipment rack.
Install separate 'clean' and 'dirty' mains outlets, wired individually back to the incoming mains distribution box. Use the 'clean' supply for
all audio equipment and the `dirty' supply for all lighting, etc. Never mix the two systems.
If necessary, to provide sufficient isolation from mains borne interference, install an isolating transformer. This should be provided with
a Faraday Shield which must be connected with earth.
Never locate the incoming mains distribution box near audio equipment, especially tape recorders, which are very sensitive to electro-
magnetic fields.
Ensure that all equipment racks are connected to earth, via a separate wire back to the star point.
Equipment which has unbalanced inputs and outputs may need to be isolated from the rack to prevent earth loops.
Audio Wiring
Having provided all equipment with power and earthing connections, consideration must be given to the method of
providing audio interconnection and adequate screening of those interconnections. This must be done in a logical
sequence to avoid problems and assist in the localisation of problem equipment.
Connect the FOH or Monitor system to the console and check for any hum, buzz, or RFI. Only when you are satisfied with the quietness
of the console and the PA system should you proceed with the next step.
Connect stereo or Multitrack Tape recorders, FX and foldback sends one at a time, checking and isolating any connection which
degrades performance.
Connect all other peripheral devices.
Connect all microphone lines.
By following this sequence much time and future trouble will be saved, and the result will be a quiet, stable system.
Shielding
Audio equipment is supplied with a variety of input and output configurations, which must be taken into consideration when
deciding where the screen connections should be made. There are three sources of unwanted signal being impressed on
the screen, which are as follows:
Extraneous electrostatic or electromagnetic fields.
Noise and interference on the earth line.
9