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 interference before switching the loop system back on.
2) Magnetic fields can be induced into any low impedance electrical path or
loop. Multiple ground earth systems may experience the pick up of the loop
signal, and cause difficulties with other systems that are not designed to
reject such interference. 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 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.
Failed AC power fuse in rear of unit
Unplug the loop and AC power supply from amplifier, and replace the failed
fuse with the spare fuse in AC power input fuse tray.
Reconnect the AC
power supply and switch on. If the fuse fails again, return the unit to
Ampetronic for evaluation - it may well be covered under warranty, which
will be invalidated by removing the cover.
If the fuse does not fail a 'loop
error' may be indicated, but shows that the unit is working correctly.
Re-connect the loop and switch the power off then on again to reset loop
error.
If the fuse fails when the loop is re-connected to the unit, then the
loop could be shorted to electrical mains (and building) earth. This can
happen even if no audio signal is present, as the short to earth is likely to
cause an instability / oscillation / feedback condition to develop. A loop
cable short to earth most commonly occurs where flat copper tape is
installed on a metal-clad raised access flooring system. If the insulation on
the flat copper tape is abraded (for example by a piece of metal swarf
trapped below the copper tape), the conductor could short to the earthed
tiles.
When installing on raised access floors, it is advisable to insulate
beneath the flat copper tape installation using Ampetronic PWT or similar
tape. The loop short to earth may only be completed when a person steps
on the tape in the affected location, which can create significant difficulties
when diagnosing the cause of fuse failure. Contact Ampetronic for further
advice if a unit is suffering recurring but untraceable failure of the rear panel
fuse.
AC Power Supply:
Output:
3-pole IEC320 connector.
NL4 speakon (1+ & 2+ connected
85W nominal for either version.
internally as are 1- & 2- to allow ‘star-
45-65Hz
quad’ method of cable connection).
Current: >9A peak (6.4A ) into 1
W
RMS
230V Version
Voltage: >20V peak (14.1V )
RMS
Nominal: 230V AC
Loop Resistance: 0.3
W
to 2.0
W
Fuse: T 630mA L
resistive or 2.2
W
max impedance
Range: 207-253V AC
reactive at 1.6kHz.
Quiescent: 100mA
THD+N <0.2% @ 1kHz @ 9.0A
pk
Typical: 400mA (O/P 3A pink noise)
RMS
Frequency Response:
120V Version
Measured at low level with no metal
Nominal: 120V AC
loss correction.
Fuse: T 1.25A L
80Hz to 6.5kHz -3.0dB
Range: 108-132V AC
100Hz to 5.5kHz ± 1.5dB
Quiescent: 200mA
Typical: 800mA (O/P 3A pink noise)
RMS
Metal Loss Correction:
0dB (flat) to 3dB/Octave boost.
Microphone Input:
Gain at 1kHz remains constant.
XLR socket.
Input Impedance: 200-600
W
Loop Monitor:
Sensitivity: -70dBu (245uV ) for full
RMS
3.5mm 3-pole (stereo) jack socket
output.
0.675Vpk at 9.0Apk output
Overload: >-5dBu (436mV )
RMS
±15V 150mA DC Output:
Line Input:
3 pin power Mini DIN socket.
6.4mm 3-pole Jack socket.
Regulated DC output for powering
Input Impedance: 1M
W
Ampetronic pre-amps & accessories.
Sensitivity: -30dBu (24mV ) for full
RMS
Environmental:
output.
Ventilation: See
Installation
section
Overload: >+20dBu (7.75V )
RMS
for details.
0
0
Ambient temperature: -10 C to +40 C
Slave I/O:
Relative Humidity: < 90%
6.4mm 3-pole Jack socket.
Input Impedance: 100k
W
Source impedance: 220
W
Output level: 0dBu (0.775V )
RMS
Compression (AGC):
>36dB dynamic range
Controlled by adjusting input level.
Standards:
Loop Design:
Meets relevant CE, EMC and
Depends on application, see
safety standards.
Designing induction loops handbook
or consult Ampetronic.
Please contact Ampetronic if you need
further assistance.
IP rating: IP20
Physical:
Weight: 3.75kg
Width: 430mm
Depth: 220mm
Height: 44mm
19” rack width, 1U high.
TECHNICAL SPECIFICATIONS
