Dc Protection; High-Impedance Warning (Open Load); Low-Impedance Protection (Short Circuit); Temperature Protection - Lab.gruppen C Series C 10 4X Operation Manual

The Attack time for the VHF protection is increa-
singly shorter at higher frequencies. For example, an
ultrasonic continuous signal will cause the outputs to
mute rapidly, where it will take several milliseconds
for a 10 kHz continuous signal to trigger the output
mute. This is shown in the illustration above.
The VHF protection is NOT a limiter and does not
alter the amplifier's frequency response. It is imple-
mented solely to detect continuous VHF content. The
amplifier will always pass VHF peaks at full power,
with no effect on musical "transients".
The VHF protection is indicated by a yellow LED on
the amplifier front panel, with output muting for 6
seconds when in action. It is reported as a fault via the
NomadLink network on the DeviceControl GUI.

7.6.3 dC protection

DC protection is implemented on each output
to prevent damage to connected loudspeakers.
DC present at the output will trigger muting and
illuminate the fault LED indicator. Any DC present
at the output indicates a hardware malfunction that
requires servicing of the amplifier.

7.6.4 high-impedance warning (open load)

A high-impedance (open load) condition is indicated
when an input signal above approximately -29dB
is detected and no functioning loudspeakers are
connected to the amplifier. The fault in indicated by
a red Sig/Hi-imp LED. The indicator is green when
a valid load is present under the same input signal
conditions
Since the high-impedance detection
initially triggers only when the input signal
rises above -29dB, it might cause the
indicator to first turn green, and then orange,
even in situations where no speaker is connected.
7.6.5 Low-impedance protection
(short circuit)
A low-impedance or short circuit fault is detected when
current draw is high (Current Peak Limiter active) and
when, simultaneously, output signal is low. When this
occurs, the amplifier protects the output stage
from damage by muting the output signal and
bypassing the circuits. Indication of this fault is a
constant orange illumination of the Current Peak
Limiter (CPL) LED on the front panel. The protection
OPERATION AND PERFORMANCE 7
will sequence at 6 second intervals to re-measure
conditions. If the low-impedance fault is no longer
detected, the amplifier will un-mute.
by an excessive input signal and is not due to a short
circuit. Turn down the input signal to avoid or rem-
edy this situation.
7.6.6
Thermal output points are shared by each channel pair.
These indicators will, if the pre-specified temperature
level is exceeded, give a high temperature warning.
This warning condition is indicated by a flashing Temp
LED on the front-panel, and it is reported on the
Device Control GUI via the NomadLink network.
As the amplifier approaches a thermal protection
threshold, the warning LED sequence will start with
short "on-time" bursts. If the amplifier continues
to overheat and approaches the temperature limit,
the flashing sequence will be defined by longer and
longer on-time bursts until the protection mode is
activated.
If the temperature becomes too high to continue
safe operation, the overheated output channel(s)
will be muted until the temperature returns to an
acceptable level.
Fully active temperature protection (with muting) is
indicated by a constantly illuminated Temp LED. It
will also be indicated as a fault via the NomadLink
network on the DeviceControl GUI.
Temperature measurements will continue at 6
second intervals. The output will un-mute when the
channel or power supply returns to a safe operating
temperature.
7.6.7
The Power Average Limiter (PAL) controls the
current-drawing relationship between the power
supply and the mains inlet. PAL limits the maximum
average power consumption according to the power
supply capabilities, ensuring that the PSU will not
overload by limiting the amplifier's maximum current
draw.
C Series C 20:8X, C 10:8X, C 10:4X and C 5:4X Operation Manual 21
If the CPL turns constant orange, the output
is muted, and the -4dB signal LED is ON,
then the amplifier has gone into maximum
current protection. This situation is caused

Temperature protection

Power Average Limiter (PAL)