Protection, Faults And Warnings - DAD FZ10004 User Manual

3.5 PROTECTION, FAULTS AND WARNINGS

Introduction
The amplifier incorporate a sophisticated and comprehensive set of protection features. Faults and warn-
ings are indicated on the front panel and reported.
Safe Operating Area detector (SOAD)
The Safe Operating Area Detector (SOAD) compares output voltage against output current to ensure that
the output transistors are working inside their safe operating area.
The SOAD provides fault monitoring and input to the Current Peak Limiter (CPL). The SOAD has no dedi-
cated indicator, and its operation is revealed only in conjunction with features such as the CPL.
Very high frequency (VHF) protection
The amplifier include protection circuits that detect continuous Very High Frequency content in the input
signal. The detection begins at approximately 10KHz and moves upwards to include ultrasonic signals If
VHF signals are detected, output will mute for 6 seconds before re-measuring.
Once no continuing 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 10KHz and
rising with a -6dB slope. This defines the VHF protection area. When continuous output power above the
threshold line is detected the VHF protection becomes active.
Output
power
20 Hz 10 kHz
The Attack time for the VHF protection is increasingly shorter at higher frequencies. For example, an ultra-
sonic continuous signal will cause the outputs to mute rapidly, where it will take several milliseconds for a
10KHz 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 amplifier's frequency response it is implement-
ed solely to detect continuous VHF content. The amplifier will always pass VHF peaks at full power, with no
effect on musical "transients".
The VHF protection is indicated by a red LED on the amplifier front panel, with output muting for 6 sec-
onds when in action. If you bench test the amplifier using a continuous, full scale sine-wave input above
10KHz, 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.
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 indi-
cates a hardware malfunction that requires servicing of the amplifier.
FZ10004
Max . Peak
output power
VHF prot ection
operation area
- 6 dB slope
Max . Continous
output power
20 kHz 30 kHz
Slow
Fast
20 Hz 10 kHz
19
Attack time
V HF protection
20 kHz 30 kHz
Fig.15