Operation Manual

5. Operation and performance
C SERIES Operation Manual rev 3.0.0
23
The Attack time for the VHF protection is increasingly 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 above.
The VHF protection is NOT a limiter and does not alter the amplier’s frequency response. It is implemented solely
to detect continuous VHF content. The amplier will always pass VHF peaks at full power, with no effect on musical
“transients”.
The VHF protection is indicated by a yellow LED on the amplier front-panel, with output muting for six seconds
when in action. It is reported as a fault via the NomadLink network on the DeviceControl GUI.
TIP: If you bench test the amplier using a continuous, full scale sine-wave input above 10 kHz, the
VHF protection will activate and prevent measurement of full peak output power. (Output will be muted
long before maximum output power is attained.) To measure the true peak output power, use a
burst signal.
5.5.4. DC protection
DC protection is implemented on each output to prevent damage to connected loudspeakers. DC present at the
output will trigger muting and illuminate the fault LED indicator. Any DC present at the output indicates a hardware
malfunction that requires servicing of the amplier.
5.5.5. High-impedance warning (open load)
A high-impedance (open load) condition is indicated when an input signal above approximately -29 dB is detected
and no functioning loudspeakers are connected to the amplier. The fault in indicated by a red Sig/Hi-imp LED. The
indicator is green when a valid load is present under the same input signal conditions.
NOTE: Since the high-impedance detection initially triggers only when the input signal rises above
-29 dB, it might cause the indicator to rst turn green, and then red, even in situations where no
speaker is connected.
5.5.6. Low-impedance protection (short circuit)
A low-impedance or short-circuit fault is detected when current draw is high (Current Peak Limiter active) and
when, simultaneously, output signal is low (-4 dB LED does not illuminate). When this occurs, the amplier protects
the output stage from damage by muting the output signal and bypassing the circuits. Indication of this fault is a
constant orange illumination of the Current Peak Limiter (CPL) LED on the front-panel. The protection will sequence