Dynacord H 2500 Owner's Manual page 33

PowerH SERIES
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
reduced. As soon as the power amp's temperature returns to a non-critical state, the ATP system
imperceptibly switches back to full supply voltage.
Thermal Limiter is the second measure that is only activated if, under extreme conditions, Voltage
Limitation is not sufficient. The thermal limiter circuit unobtrusively reduces the amplification of the power
amplifier. Only if even this measure does not re-establish thermal balance, the ATP system activates
Thermal Mute as the last step to completely switch off the signal path.
This step-by-step functioning of Advanced Thermal Protection enables PowerH SERIES amplifiers to still
be in operation under conditions where various other amps would have ceased operation.
The PROTECT-LED lights immediately to signal a direct intervention in the signal path by limiters and a
corresponding indicator in IRIS-Net™ allows the FOH-engineer to react instantly, even before interference
with the audio performance becomes noticeable.
Monitoring Ambient Temperature
PowerH SERIES amplifiers constantly monitor the temperature of several active electrical components
during operation. In addition, monitoring also includes the temperature of the inlet cooling air and as a
result also the temperature of the power amp's ambience. If, for any reason the ventilation louvers are
totally blocked or the inlet outer air exceeds the upper temperature limit for effective cooling, this would
inevitably lead to overheating of the power amplifier. This condition can possibly occur even when the
power amplifier is in idling mode, for example when it is installed in a closed rack case.
However, during idling the preventive measures of the Advanced Thermal Protection (see previous
paragraph) show hardly any impact. For this reason the power amplifier enters standby mode once it is
operated under extreme thermal load, which is caused by inadequate cooling. In that case, PROTECT-
LED and STANDBY-LED blink alternately.
Owner's Manual 33