Ampetronic d series, Инструкция по установке и эксплуатации

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Ampetronic D Series Installation Handbook & User Guide Page 35
monitor socket. Channel A = left, channel B = right .
CLIP LED
s
illuminated
Indicates that the output voltage is clipping . Occasional lighting of this indicator is normal on peaks
of signal .
• Turn down the CURRENT control on the channel(s) in question to avoid causing the output
voltage to clip .
• Check the loop is not open circuit, short circuit, or connected to earth (see instability or high
frequency noise section of Troubleshooting)
• Check the loop is within specified limits.
Low magnetic field strength
Due to insufficient CURRENT or excessive metal loss.
May require a special loop design to achieve acceptable performance, contact Ampetronic for
advice .
Instability or high frequency noise
1 . It is possible for the loop cables to be grounded under fault conditions, resulting in instability
which may sound like high frequency noise, buzz or whistling . The results of this type of fault
are unpredictable and may appear as any combination of the front panel indication errors
2 . This fault is easy to determine. Simply unplug the loop cables from the amplifier and test
with a resistance meter between either of the loop wires and a good earth point such as a
metal radiator. There should be an infinitely high reading i.e. no connection at all. Any reading
indicates a failure of the loop cable insulation and you will need to either repair or replace the
loop cable .
3 . Instability can be caused by using poor quality signal cables, long unbalanced (2-wire)
signal runs to the inputs, or by running input cables in close proximity with the loop wire over
an appreciable distance. Loop amplifiers are capable of delivering high currents at audio
frequencies . If the loop cables are run close to sensitive signal cables it may be possible to
induce a signal back into the input of the amplifier causing feedback. Cable runs and loop
wires should be kept well apart from each other . To avoid interference maintain a separation of
at least 300mm .
4 . Instability can cause the amplifier to run hot and may result in the TEMP LED illuminating.
Interference
1 . Background magnetic field signals or interference may be present in any location and may not
be anything to do with the loop system. Monitor this with a loop receiver (such as an ILR3). If
the interference is still present with the loop system switched off, then you need to locate and
eliminate the source of the interference before switching the loop system back on
2 . Magnetic fields can induce currents into any low impedance electrical path or loop. Audio or
video systems with multiple earths may experience pick up of the loop signal . Check entire
sound system for evidence of loop signal, and trace source of pick up .
3 . Under certain circumstances, the loop signal may appear as jagged lines or hum bars on a
CCTV picture. This could be due to running CCTV (low impedance unbalanced 2-wire circuit)
cables in close proximity to the loop cable . Separate the loop cables to reduce the effect .
4 . Remote (and apparently unconnected) PA systems can sometimes pick up loop signals. This
is usually because the loop cable becomes damaged (see point 1 of Instability) or induces
signals into the remote system through long unbalanced cables . Always run long audio signal
cables as 3-wire balanced circuits and keep away from loop cables .
5 . See also point 1 of Instability