Allen&Heath Scepter USER GUIDE - Manual (Page 8)

Audio Owner Manual Section 1
INSTALLATION
Unpack the unit from the packing carton. Remove the power supply unit from
the packing. We recommend that you keep intact this purpose designed packing to
should you need to ship the unit in the future. Please ensure that the Scepter
unit, power supply and other items are correctly repacked to avoid transit damage.
Please ensure that the fader knobs are in the up position.
Check that the AC operating voltage marked on the power unit is the same as
the local supply.
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Connect the DC power cord from the power supply into the rear panel of the
Scepter unit. Ensure that it latches firmly.
Earthing/Grounding in the audio system
There two important reasons why it is necessary to ensure that your audio
system is well earthed (grounded).
Safety prevention of electric shock (see previous section on SAFETY)
Shielding preventing external electrical interference from causing noise in the
audio signal path.
In addition to solving noise and interference problems, earthing can also
cause them. If there are multiple earth paths in a system then an “earth loop” can
be formed. This usually results in an excess hum in the system, but can also cause
the breakthrough of RF and other noises.
The preferred method to overcome earth loop problems is to earth all pieces
of equipment separately to a good “star point” mains earth and to break potential
earth loops by disconnecting the screens of the audio cables at one end, usually
the signal destination. If excessive RF interference is present this may be reduced
by connecting the screen to earth through a small value capacitor, typically 0.01
microfarad
Alternatively; just one piece of equipment, usually the power amplifier, is
connected to mains earth and the other equipment earthed via the interconnecting
cable screens which must be connected at both ends. However, having only one
unit connected to mains earth means that all of the other pieces of equipment rely
on the audio cable screen for safety. It is important to remember this. Test
regularly, that all exposed metal equipment including microphones, guitar strings
and DI boxes have a low resistance to mains earth.
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