Lab.gruppen C Series C 16 4 Operation Manual - page 11
C Series C 68:4, C 48:4, C 28:4 and C 16:4 Operation Manual 21
20 C Series C 68:4, C 48:4, C 28:4 and C 16:4 Operation Manual
7.5.7 Temperature protection
Thermal measurement points are provided on each
output channel as well as on the power supply. If
these sensors detect temperatures above the speci-
fied maximums, a high temperature warning will be
indicated by a flashing Temp LED on the front panel.
The warning also will be transmitted to 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.
7.5.8 Power Average Limiter (PAL)
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. In addition, in the larger models that
potentially could pull more current from the mains
than the mains fuses are specified to handle (more
than 16 A), PAL limits the amplifier’s maximum
current draw to prevent blowing the mains fuse.
7.5.9 Soft-Start
High powered amplifiers with inadequate inrush
limiting can pull considerable current from the
mains at turn-on. This can result in fast acting mains
breakers tripping. Such is not the case with C Series
amplifiers. The C Series amplifiers have very low
inrush power as the capacitors are charged slowly
and in a controlled manner ensuring that breakers
will not trip.
Several amplifiers will, under normal conditions, be
able to be powered up simultaneously. If you do
experience problems powering up multiple amplifiers
simultaneously, use the NomadLink network and the
NLB60E to establish a power sequence with pre-set
delays between the start-up of each subsequent
amplifier.
7.6 front-panel monitoring and
adjustments
7.6.1 Level indicators
Four signal/level/clip LEDs per channel are contained
on the C Series front-panels :
Orange
•
CPL (Current Peak Limiter) flashing
indicates signal exceeds the limits of the output
devices and limiting is in effect.
Red
•
VPL/CLIP indicates that the signal has
exceeded maximum output voltage. (Maximum
voltage is determined by rear-panel VPL set-
tings.)
Green
•
- 4 dB indicates output signal has reached
this level.
Green
•
- 10 dB indicates output signal has reached
this level.
Signal / hi-Imp
•
(Green/red) indicates an output
signal above -44 dB. If it turns RED, this indicates
that a high-impedance (“open” connection) has
been detected at the output. This can be a fault
such as a disconnected cable or malfunctioning
loudspeaker driver. However, it could indicate
acceptable high impedance, such as a sub-bass
enclosure with high-impedance at a certain
frequency. When the -10 dB signal LED is on
AND the Hi-Imp. LED turns red then the ampli-
fier has detected an open load (no speaker is
connected).
For more detailed signal level indications use the
DeviceControl software application.
7.6.2 Level adjust
Step Attenuation
1 (Min)
-Inf. dB
2
-Inf. dB
3
-50 dB
4
-40 dB
5
-35 dB
6
-21.5 dB
7
-21.5 dB
8
-14.7 dB
9
-12.9 dB
10
-11.4 dB
11
-10.0 dB
12
-8.7 dB
13
-7.4 dB
14
-6.0 dB
15
-4.5 dB
16
-2.7 dB
17
-0.6 dB
18
-0.3 dB
19
-0.1 dB
20
0 dB
21 (Max)
0 dB
Level adjust potentiometers (one per channel) are
located behind the removable dust-filter cover on the
amplifier’s front-panel. It is not possible to adjust the
level settings with the cover in place.
The potentiometer’s operational range is 0 dB to
-infinity in 21 steps. Attenuation is logarithmic, with
12 o’clock position being -10 dB. See table to the
right with increments.
It is not possible to adjust the individual channel
attenuation from the NomadLink network or
elsewhere on the amplifier.
Use fingers or a screwdriver to adjust the potenti-
ometers.
7.6.3 Mute indication
Individual channel Mute is indicated by illumination of
the two yellow LEDs at the top of the channel’s LED
bargraph. If both LEDs are illuminated and all other
indications are normal, then the channel has been
muted by a command from the NLB 60E front-panel
or the DeviceControl application. Otherwise, a Mute
could indicate a fault condition. (See below)
7 OPERATION AND PERFORMANCE
OPERATION AND PERFORMANCE 7