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FM-55 / Aug 2014
G E N E R A L I N F O R M A T I O N
AM-55 Installation Tips
Grounding
Establish a low impedance common ground in the facility and try to route all
equipment grounds to that point. Use ground conductors with the largest possible
surface area and keep ground leads as short as possible. The AM-55’s ground reference
is its chassis, which should be connected to the station ground. Such a connection is
especially important when the AM-55 is operated in a high RF environment because it
helps minimize differential voltages between the processor’s chassis and other pieces
of equipment such as the rack it is mounted within.
Surge Protection
Always place surge protection circuits as close as possible to the device being
protected. AC power line surge protection should manage transients in a way that keeps
instantaneous potential differences between the power line hot, neutral, AC grounding
conductor, the station ground, and the processor chassis as low as possible. Likewise,
measures should also be taken to keep the instantaneous potential difference between
the audio cable shields and the processor chassis as low as possible (this applies to
all audio equipment, not just the AM-55), particularly when the equipment is located
within the electrically hostile environment of a station’s transmitter facility.
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 UPS behave when AC power is not exactly 60Hz, such as when
the facility is on its backup generator?
- If the UPS has onboard surge protection, what kind of surge capability does it
have and where are those surges directed to?
- Is the UPS equipped with remote monitoring capability?
- Does the UPS have onboard monitoring and alarms to signal problems such as
low batteries?
Analog Audio Input Connections
Balanced audio input sources should be connected to the AM-55 using standard
two-conductor shielded audio cable such as Belden 8451 or 9451.
Unbalanced input audio connections
should be made with shielded two
conductor cable. At the unbalanced
source’s output connect the “+” output
to AM-55’s “Hi” input (XLR pin 2) and
connect the shield wire to the AM-55’s
“Lo” input (XLR pin 3). If the cable’s
shield is used (recommended) connect it
at the AM-55 end only (XLR pin 1) to
prevent AC ground loops.
