LabGruppen DSP24 User Manual
C Series: Installation-Dedicated Amplifiers
20 Hz 10 kHz 20 kHz
30 kHz
- 6 dB slope
VHF protection
operation area
Max. Peak
output power
Max. Continous
output power
Output
power
Attack time
VHF protection
Slow
Fast
20 Hz 10 kHz 20 kHz
30 kHz
Technology Brief:
Protection Features
When it comes to causing problems, power amplifiers are unique
inaudio systems. Whereas faults in other devices are usually
confined within the device itself, failures – or extreme abnormalities
– in a power amplifier can have devastating secondary effects. In
some cases, costs for damage to connected loads can far exceed
the cost of the amplifier.
In other, less dire circumstances, inadequate protection features
can cause short-term service interruptions due to muted outputs
or tripped mains breakers. Such temporary interruptions can prove
costly in terms of lost clientele or audience dissatisfaction.
To minimize any likelihood of either equipment damage or ser vice
interruptions, C Series amplifiers from Lab.gruppen are equipped
with the industry’s most comprehensive suite of protection,
monitoring, and fault warning features.
Current Protection Limiting (CPL) and Safe
Operating Area Detection (SOAD)
Technology: Current Peak Limiting (CPL) and Safe Operating Area
Detection (SOA D) are two related features that work in concert
to ensure that the amplifier output stages always operate within
defined parameters, safeguarding the critical output transistors. The
SOAD circuits constantly monitor the outputs and compare voltage
against current to make sure the output transistors are working
inside their safe operating area. This sensing circuit works in
conjunction with the Current Peak Limiter (CPL), which applies
dynamic gain reduction only when the output devices draw current
outside their safe operating area. Activity of the CPL is indicated by
a flashing LED on the front panel, and by a CPL warning on the GUI
of NomadLink’s DeviceControl software. The CPL is non-adjustable:
fixed thresholdvalues are determined by the model t ype, ranging
from 24.5 Arms on the C 68:4 to 8.5 Arms on the C 16:4.
Lab.gruppen’s NomadLink monitoring and control network.
Benefits: VPL keeps the amplifier operating safely within it’s
hardware capabilities, as well as providing a smooth and well
controlled output signal even when the amplifier is driven into
clipping. VPL’s output power management allows the same amplifier
to be configured for use in several different applications. For example,
in a smaller theater or house of worship application, a single amplifier
could use one or two output channels (separately or bridged) for the
subwoofers, one or two channels for the full-range FOH cluster, and
the fourth channel to drive a constant voltage system
Power Average Limiter
Technology: The Power Average Limiter (PAL) is a unique feature
that controls the flow of line current into the power supply. Power
consumption is limited to the amount that falls within the design
parameters of the power supply, ensuring that the PSU will never be
overloaded. Also, higher power models in the C Series can potentially
draw more current (with output devices still within safe operating
areas) than is allowed by the safety-mandated mains fuse. In this
case, the PAL limits average current draw to protect the mains fuse.
Benefits: PAL keeps current draw within operating limits to prolong
operational life of the PSU, and prevents blowing of the mains fuse
on higher power models.
Very High Frequency (VHF) Protection
Technology: C Series amplifiers are designed to reproduce high
frequency audio signals nearly a full octave above those audible
to typical adult listeners. This high-end bandwidth contributes to
the renowned transparency and pristine transient response of
Benefits: CPL and SOAD work together to prevent excessive output
current that could damage output transistors.
Voltage Peak Limiting (VPL)
Technology: Voltage Peak Limiting (VPL) keeps the amplifier
working within its safe operating limits. In addition, VPL makes it
possible to scale the peak voltage in eight steps, adjusting the
Voltage clip level - and thereby the output power - to various connected loads. This applies to both constant voltage systems (70 V and
100 V), as well as when output power needs to be adjusted to suit
a lower rated load. For constant voltage systems, setting the VPL is
simply a matter of selecting the voltage setting corresponding to the
system type. (The 141 V peak, for example, equates to 100 Vrms.)
For various low impedance loads, Lab.gruppen provides charts in
the C Series manual and on the Lab.gruppen web site that can be
used as guides for optimum setting of the VPL function. Also, a load
setting calculator is built into the DeviceControl software used with
Technology Brief : Protection Features
TEMP
MUTE
BRIDGE BRIDGEBRIDGE BRIDGE
MUTE
FAULT FAULT
TEMP
POWER
AFS
OPTION
CH|A CH|B CH|C CH|D
VHF VHF
CPL CPL
VPL | CLIP VPL | CLIP
-4dB -4dB
-10dB -10dB
SIG | HI-IMP SIG | HI-IMP
POWER
REMOTE
Lab.gruppen amplifiers. However, musical transients last only a
fraction of a second. Continuous very high frequency content does
not exist in normal program material, and is potentially damaging to
connected high frequency drivers. All C Series amplifiers include
a sophisticated VHF detection circuit that effectively discrimi nates between musical content and spurious signals. The circuit’s
operational area factors in output power, frequency and duration.
Detection begins at about 10 kHz for maximum peak power, and
continues at a -6 dB slope. The higher the frequency, the lower the
power level for detection. The attack time for implementing protection
decreases at higher frequencies, allowing some sustained activity at
10 kHz but acting very rapidly above 20 kHz. The VHF protection has
no limiting function; all signals are passed at full power with no effect
on transient material. However, should dangerous VHF content be
detected, the output will mute for six seconds; if no further VHF
content is detected, the output automatically un-mutes. Simultaneously, a fault condition is shown on a front panel LED and
transmitted via NomadLink for indication on the DeviceControl
software GUI.
Benefits: Protection of connected high frequency drivers with no
effect on the amplifier’s high-frequency transient response.
Temperature Protection
Technology: C Series amplifiers offer cooling facilities that far exceed
the industry norm, including robust cooling fans and a proprietary
Intercooler® copper heat sink with thousands of tiny cooling fins.
Nevertheless, overheating can result from environmental and
operational factors: blocked airflow, high ambient temperature, or
prolonged operation at or near current output limits. To guard against
service interruptions or damage, the C Series has implemented
comprehensive over-temperature warning and protection measures.
Thermal measurement points are located on each output channel
and in the power supply. When a pre-set temperature threshold is
reached, a warning status is displayed on the front panel (flashing
LED) and on the DeviceControl GUI via NomadLink. As the critical
temperature threshold approaches, longer warning flashes are given.
When temperature exceeds the critical limit, the output channel
will mute. Temperature is re-measured every six seconds, and the
channel un-mutes when temperature drops to safe levels. Power
supply over-temperature protection operates in a similar way, but
indirectly. There is no separate indicator or action for it, instead it
effects the individual outputs (“hottest first”).
Benefits: Output transistors and power supply components are
protected from damage due to excessively high temperatures.
High Impedance/Open Load Warning
Technology: C Series amplifiers are equipped to sense an open or
extremely high impedance load condition whenever a signal above
approximately -29 dB is present at the input. When this situation
is detected, a warning LED lights on the front panel and indication
is given on the DeviceControl software GUI via the NomadLink
network.
Benefit: Operator is notified of possible fault in wiring or connected
loudspeakers.
Extreme Low Impedance / Short Circuit
Protection
Technology: C Series amplifiers are designed to accommodate
load impedances as low as 2 ohms. However, any sustained
impedances below this level usually indicates a wiring fault or short
circuit. The C Series amplifier detects this condition when current draw
is high (activating the Current Peak Limiter) while simultaneously the
output signal is low. Under these conditions, the output is muted. The
protection circuit sequences at six second intervals; if the fault
condition is no longer detected, the output channel will un-mute.
Benefit: Output transistors are protected from damage, and further
damage to connected loudspeakers is possibly avoided as well.
DC Protection
Technology: All C Series amplifiers incorporate circuits that will
immediately sense the presence of DC at the outputs. Since
DC is never present under normal operating conditions, any DC
component indicates an internal fault
condition requiring repair. The output is
muted (electronically disconnected) and the
corresponding fault condition is shown
on the front panel LED display and on the
Device Control software GUI via NomadLink.
Note that only the channel showing DC
fault will mute; other amplifier channels will
continue to operate.
Benefit:Connected loudspeakers are protected from potential
damage.
Soft Start
Technology: When first tuned on, high -power amplifiers can draw
a considerable amount of current from the AC mains. If two or
more are turned on simultaneously, this can trip the mains breaker.
C Series amplifiers implement a slow, controlled charging of
capacitors to limit current inrush.
Benefits: Several power amplifiers may be turned on simultaneously
with greatly diminished chance of tripping the mains breaker.
(Note:The NomadLink network and NLB 60E bridge provide facilities
for sequential turn-on in larger installations.)
i n t e r n a t i o n a L c o n t a c t • t e L + 4 6 ( 0 ) 3 0 0 5 6 2 8 0 0 • i n f o @ L a b g r u p p e n . c o m
u S c o n t a c t
L a b . g r u p p e n a b • S w e d e n
• T E L ( 8 1 8 ) 6 6 5 4 9 0 0 • i n f o u S @ t c e L e c t r o n i c . c o m
w w w . l a b g r u p p e n . c o m
Item no. PF-CS
Loading...