Wheatstone FM-531 HD, Technical Manual

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FM-531HD / May 2013
G E N E R A L I N F O R M A T I O N
UPS/Power Conditioning
Choose the best power conditioning/UPS units that your budget will allow, focusing
on the most important features and options that you actually need. Some questions to
ask while reviewing features are:
- How does the unit handle AC power that is not exactly 60Hz, such as when the
facility is on its backup generator?
- If the unit has onboard surge protection, what kind of surge capability does it
have and where are those surges directed to?
- Is the unit equipped with remote monitoring capability?
- Does it have onboard monitoring and alarms to signal a problem such as batteries
with low reserve?
Analog Audio Input Connections
Balanced audio input sources should be connected to the FM-531HD using standard
two-conductor shielded audio cable such as Belden 8451 or 9451.
Unbalanced input audio connections
should be made with shielded two con-
ductor cable. At the unbalanced source’s
output connect its “+” output to processor’s
“Hi” (XLR pin 2) input and connect the
shield wire to the “Lo” (XLR pin 3) input. If the cable’s shield is used (recommended)
connect it at the hardware end only (XLR pin 1) to prevent AC ground loops.
If RF interference is an issue, the far
(floating and ungrounded) end of the
cable shield can be experimentally by-
passed to RF ground via a 0.01µF, 250V
AC capacitor. Suitable capacitors are:
TDK CS17-F2GA103MYGS
Murata DE2F3KH103MA3B
Panasonic ECK-ATS103MF
AVX 65N103MBLCP
Field experience indicates that the listed capacitors can handle the reasonably high
RF currents that might exist on audio cable shields at AM and FM transmitter sites.
Analog Audio Output Connections
Balanced audio loads should be connected to processor’s outputs using standard
two-conductor shielded audio cable. Unbalanced audio loads should be avoided, but
if they can’t they should be connected using shielded two conductor cable such as
Belden 8451 or 9451 (as if connecting a balanced source).
The FM-531HD is equipped with active balanced output stages that behave like
a transformer. Because of this behavior the wiring may be different than expected.