General Wiring Procedures - SoundCraft K1 User Manual

General Wiring Procedures

Initial Wiring
Considerations
Installation
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.
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, vending machines 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.
December 1994 2.5