Cloud Electronics 46-120TMedia - Manual (Page 32)

46-120 Installation and User Guide V1.2 32
PSU capability and optional device
current consumption
In addition to supplying the Mixer Amplifier’s circuitry, the
internal PSU has the capacity to power some additional items
which may form part of a complete system. These include
LM-2 active remote input modules (via the Facility Port),
loudspeaker EQ cards (fitted internally), and possibly a PM
Series paging microphone (powered via an optional CDI-46
Digital Interface card).
The maximum current capacity of the PSU available for
powering additional items is 250 mA. Individual device
component limits are as follows:
• 150 mA for internal EQ cards
• 50 mA for LM-2s via the Facility Port
• 240 mA for PM Series paging mics via the
CDPM/PM
port
Current consumption of the various items is listed in the
table below.
ITEM CURRENT PER UNIT
LM-2 mic/line input module 25 mA
PM4 paging microphone 72 mA
PM8 paging microphone 83 mA
Loudspeaker EQ cards (each) see note*
*Model-dependent. See separate datasheets at www.cloud.co.uk
The installer should ensure that the total current drawn by
all the additional items in a system does not exceed 250 mA
under any circumstances. If, for example 150 mA is needed by
EQ cards and 25 mA by an LM-2, only 75 mA is available for
a PM4 or PM8 paging microphone. If no EQ cards or fitted
and there are no LM-2s in the system, then the full 250mA is
available
Note that PSU performance – and hence current
availability - will be degraded at ambient
temperatures in excess of 35°C.
EMC considerations
The Cloud 46-120 fully conforms to the relevant
electromagnetic compatibility (EMC) standards and
is technically well behaved; you should experience no
operational problems and under normal circumstances, no
special precautions need to be taken. If the unit is to be used
within close proximity to potential sources of HF disturbance
such as high power communications transmitters, radar
stations and the like, the performance of the mixing amplifier
may be reduced; we suggest that the microphone cable screen
be connected to the shell of the XLR type connector and the
line input leads are kept as short as possible.
Ground loops
If, despite your best efforts, the completed sound system
‘hums’ you probably have a ‘ground loop’. The offending signal
source can often be identified by setting the volume control
to minimum, then disconnecting the input leads (both left &
right channels) on each line input until the ‘hum’ disappears.
This problem is often caused by terminating a screened input
cable into a signal source positioned a significant distance
from the mixer. A good way of avoiding this potential problem
is to use signal sources (typically ‘consumer’ equipment) that
are double insulated with no connection to the mains supply
earth. If a signal feed were derived from a second mixer (a
club or microphone mixer for example) it would be perfectly
normal to expect this to be earthed; we suggest that a
transformer be used to isolate the signal and prevent a noisy
loop (see page 14).