C Series C 20:8X, C 10:8X, C 10:4X and C 5:4X Operation Manual
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4.2.2 Amplifier gain
For greater flexibility in system integration, C...X
amplifiers allow gain adjustment from +29 to +38
dB in 3 dB steps. If the input signal is weak, the
gain can be boosted to maintain maximum power
output while avoiding a poor signal-to-noise ratio. This
gain adjustment feature makes it easier to achieve
an optimal balance between headroom and noise
floor.
4.2.3 Voltage Peak Limiter (VPl)
The Voltage Peak Limiter (VPL) feature allows
user adjustments that determine maximum voltage
output, thus matching the amplifier to the connected
speaker load. Whether the connected load is low-im-
pedance (2 to 16 ohms) or high-impedance (70 Vrms /
100 V peak), the VPL feature can be set to ensure that
neither temperature nor current limitations are
exceeded before reaching the desired voltage
threshold.
4.2.4 Protection and performance
optimization
Appropriate and reliable power amplification is vital
to any audio system. Inadequate or faulty power
amplification could cause damage to the loudspeakers,
or in some cases to the power amplifiers themselves.
To prevent any damage or costly service interrup-
tions, C Series amplifiers offer advanced features
to protect both internal circuits and any connected
loads. These features even protect the mains fuse
that, in extreme cases, could be overloaded.
Following are short descriptions of standard built-in
C Series protection features:
CPL
•
(Current Peak Limiter) ensures that the
amplifier’s output does not exceed the safe
current handling parameters of the amplifier
components.
Temperature protection
•
ensures that the
amplifier will not be damaged by exceeding
thermal limits.
PAL
•
(Power Average Limiter) limits the maximum
average power consumption according to the
power supply and mains-breaker capabilities.
Vhf
•
(Very High Frequency) protection circuits
mute the output of the amplifier when non-
dynamic continuous signals above 10 kHz are
detected.
dC protection
•
ensures destructive DC signals
will not appear at the amplifier outputs. If such
conditions occur an internal fuse opens and fault
indication is displayed.
Low-impedance
•
(short circuit) protection
provides a fault warning indication and shuts
down the output stage when, for example, an
input signal is present and a malfunctioning cable
or driver is short circuiting the output.
high-impedance
•
warning reports an alert when
output signal is high, and simultaneously, no
current draw is measured. This situation might
occur when no speakers are connected, or when
a driver is blown.
Low inrush current
•
ensures that the mains
breaker will not trip when several power
amplifiers are turned on simultaneously.
4.2.5 GPIO facilities and 35 hz hPf
Lab.gruppen C…X amplifiers offer two features
that provide greater flexibility and reliability in fixed
installations: GPIO (General Purpose Input / Output)
facilities and a 35 Hz high-pass filter.
The GPIO connections allow seamless interfacing
with many third-party control and power sequencing
systems. In combination with the rear panel DIP-
switch, the GPIO connections allow change-of-state
power toggling from two inputs (each closure toggles
on-to-off or off-to- on), or same-state on/off from a
single input (closed = on and open = off). A second
DIP-switch disables the power on/off commands from
the NomadLink network, allowing only GPI contact
closures to trigger power on/off commands.
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