SoundCraft CPS275 - Manual (Page 10)

Recommendations for Installation
The CPS250/CPS275 power supply is provided with front panel fixing holes for 19"
rack-mounting and will occupy 2U of rack space.
As with any power supply that contains a large mains-voltage transformer, it is
preferable to provide a degree of physical isolation of the unit from other electronic
equipment, particularly that which carries low level audio signals, to avoid any
possible hum pick-up. For this reason the unit is used with a long (7 metres) output
cable to enable it to be positioned away from the mixing console.
For the same reason, when rack-mounting it is preferable to avoid locating the unit
adjacent to signal processing equipment.
It should be noted that if a complete rack containing a CPS250/CPS275 unit is to be
operated from a different mains supply level, then the unit should be withdrawn from
the rack in order to reselect the mains voltage setting, at the same time as resetting any
other equipment.
The other important consideration when rack-mounting the unit is the need for natural
convection of air over the case and an unrestricted air flow through the unit. Note that
air is drawn in at the rear of the unit and expelled through the front panel.
Good ventilation BELOW the unit, in the floor or back of the rack, and similarly
ABOVE the unit, at the top of the rack, will ensure a path for continuous air flow.
Other equipment in the rack which is known NOT to produce a significant amount of
heat should be mounted BELOW the unit. Equipment that also relies on good air flow
within the rack (ie. most power amplifiers and other power supplies) should be given
due consideration and some space should be provided between such units and between
these and the CPS250/CPS275 unit. Forced convection, by means of a fan-tray, may
be desirable in this situation.
The CPS250/CPS275 will operate as a free-standing
unit without requiring any special cooling
arrangement, but should not be allowed to be
accidentally or deliberately covered over in any way.
Do not operate the unit with the top cover removed.
The air intake and outflow holes must be inspected
regularly and cleaned if necessary to maintain good
airflow through the unit. This will be particularly
important if the unit is used in a dusty environment.
Finally, some consideration should be given to the earthing arrangement of the system
at the centre of which are the console and the CPS250/CPS275 (and any other
Soundcraft power supply units). The console chassis is earthed, through the mains
earth, via the power supply. When rack-mounting the CPS250/CPS275(and any other
Soundcraft power supply units) care should be taken to avoid any possible ‘ground
loops’ in the system which would introduce audible hum to otherwise clean audio
signals. Ground loops may occur where signal processing equipment, patched to the
console, has its signal earth commoned to the equipment chassis. The ground loop is
6 Installation