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PowerH SERIES
Owner’s Manual 33
The power amp’s CPU is acquainted with the temporal progression of the mains current consumption and
therefore can simulate the typical behavior of a mains circuit breaker. Nevertheless, pulse peaks allow
crest currents that can exceed the nominal value by a multiple. RMS measurement of the mains current
consumption allows the CPU to emulate the temperature curve of a circuit breaker’s thermal trip, which in
return enables the Mains Circuit Breaker Protection to let the power amplifier work till shortly below the
trigger level of the automatic circuit breaker. With typical concepts, especially for those without RMS
current measurement, output power reduction has to be applied much earlier. During the processing of
musical program material, the Mains Circuit Breaker Protection normally does not have to reduce the
power amp’s output power. At most, with settings that are noticeably below the pre-set values of 16 A or 30
A respectively, (which may be reasonable when operating multiple power amps via a single automatic
circuit breaker) output power reduction might become necessary to prevent the mains fuse from blowing.
Power-On Delay and Softstart
A Power-On Delay of up to 6.35 seconds can be programmed for the power amp via the LC display. Upon
pressing the mains switch the power amplifier does not start until the set delay time has elapsed. If several
power amps are operated on the same automatic circuit breaker, cascaded switch-on can be accomplish
by programming individually different power-on delays for the amps. This also prevents the magnetic trip of
an automatic circuit breaker from acting and thus disconnecting the power amplifiers from the mains
supply, when various amps are switched on at the same time. The internal soft-start function additionally
suppresses current peaks during power-on, which ensures trouble-free operation of PowerH
SERIES amplifiers even on very sensitive automatic circuit breakers.
Output Short Circuit Detection
The corresponding output voltage and output current is measured for both output channels as soon as the
power amplifier processes an audio signal. These readings are used to monitor the connected
loudspeaker loads. The power amplifier has the ability to continuously deliver very high output currents.
For example, if, in spite of a low output voltage, the current flow is high as the consequence of a short-
circuit in one of the speaker lines, the power amp detects this fault condition and immediately disables
signal output to protect connectors and cables against damage from overload. This, of course, also
protects the power amplifier itself from being damaged by excessive electrical or thermal overload.
Advanced Thermal Protection
The PowerH SERIES amplifiers are the first to feature the new Advanced Thermal Protection
(ATP). This new system differs in a trend-setting manner from traditional thermal protection measures,
which, as soon as the fans are not any longer capable of dissipating the lost heat, mostly switch off the
entire signal path at a relative early stage. With the ATP system switching off the signal path is last of three
consecutive measures. Prior to making this final step, the system uses two other approaches to limit the
amp’s power, so that it returns to a thermally stable operational range.
The first step is Voltage Limitation. This measure reduces the internal supply voltage of the power amplifier
blocks, which, objectively, is at the expense of reducing the voltage dynamic. During the reproduction of
music or speech, however, this effect is subjectively hardly perceived. Despite the negligible acoustic
influence, the efficiency gained in the power amp is so high that the development of heat is clearly