Lab.gruppen C Series 5:4X - Manual (Page 28)

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C Series C 20:8X, C 10:8X, C 10:4X and C 5:4X Operation Manual rev. 1.1.4
Operation and Performance
The following additional technical information
describes GPI port functionality:
Maximum “open” contact voltage: 5 V
Maximum “closed” contact current: 1 mA
Maximum resistance for “closed” contact: 1 kOhm
5.5.4 NomadLink disable switch
The DIP-switch labeled “GPI (➟NomadLink)” completely disables the amplifier’s connectivity to the NomadLink
network.
5.6 Protection, faults and warnings
5.6.1 Introduction
C Series amplifiers incorporate a sophisticated and comprehensive set of protection features. Faults and
warnings are indicated on the front-panel and reported via the NomadLink network for indication on the
DeviceControl GUI.
5.6.2 Very High Frequency protection
All C Series amplifiers include protection circuits that detect continuous Very High Frequency (VHF) content
in the input signals. The detection begins at approximately 10 kHz and moves upwards to include ultrasonic
signals If VHF signals are detected, the output will mute for six seconds before re-measuring. Once no continu-
ing VHF signal is detected, the output un-mutes and returns to normal operation.
This feature recognizes that continuous full-scale VHF signals do not appear in “natural” sources such as
music. Any such signals can therefore be considered as a fault when present. VHF protection is essential in
avoiding damage to high frequency drivers.
The VHF protection operational area is dependent on output power level and frequency. The illustration below
shows a decreasing threshold on the output power level, starting at approximately 10 kHz and rising with a
-6 dB slope. This defines the VHF protection area. When continuous output power above the threshold line is
detected the VHF protection becomes active.
The Attack time for the VHF protection is increa-singly shorter at higher frequencies. For example, an ultrasonic
continuous signal will cause the outputs to mute rapidly, where it will take several milliseconds for a 10 kHz
continuous signal to trigger the output mute. This is shown in the illustration (figure 7.6.2).
The VHF protection is NOT a limiter and does not alter the amplifier’s frequency response. It is implemented
solely to detect continuous VHF content. The amplifier will always pass VHF peaks at full power, with no effect
on musical “transients”.