Cerwin-Vega CXA-10 Manual - Manual (Page 6)

PROTECTION
Every model in the CXA-Series incorporates protection features.
The front panel Protection LED indicates the activity of the
speaker connection relay circuitry in each channel.When the
protection LED turns on, this circuitry is active, and all connected
speakers are muted.
Initial power-up : For approximately five seconds after initial
power-up, the protection circuitry is activated and the speaker
outputs are muted. If everything is operating normally, you will
hear an audible click at the conclusion of this brief period, as
the protection circuitry is deactivated and the unit begins
delivering signal to the connected speakers. It is normal for the
Protection LED to fade gradually after the amplifier is powered
off.
Thermal Protection : Abnormally high heat sink temperatures
will engage the protection circuitry for the overheating channel
only. An output relay disconnects the speakers until normal
temperature range is restored. The Protect indicator will light
to show the protection circuit is active. To guard against this
problem, make sure the unit receives adequate ventilation on all
sides and that both the front and rear panels are unobstructed.
If the power transformer gets too hot, its thermal switch will
disconnect all of the secondary power and disconnect both
channel outputs.
Short circuit : If output is shorted due to faulty wiring, the
thermal circuitry will automatically protect the amplifier. If this
occurs, the load will be disconnected by the thermal protection
circuitry.
DC Voltage Protection : If an amplifier channel detects DC
voltage at the speaker output, the output relay will immediately
open to prevent speaker damage.
Subsonic Frequency Protection : The built-in High Pass Filter
provides subsonic frequency protection for each channel.
Current limiting Protection : At the amplifier’s full power limit,
or clipping point, the limiter circuitry will be activated. This is
indicated by illumination of the Clip LED. The channel gain is
automatically reduced, protecting the speakers from high
power. Uncontrolled feedback, oscillations, or improper
equipment gain setting may activate this circuitry, which is
virtually transparent in operation as full signal bandwidth is
maintained.
There is reason to be concerned any time the Protection LED
lights up (except for initial power-up during approximately five
seconds). If this occurs, turn the amplifier off immediately and
SETUP
Clipping is the result of an amplifier running into power supply
limitation. The maximum output voltage that any amplifier can
produce is limited by its power supply. Attempting to output a
voltage (or current) level that exceeds the power supply limit
will result in a flattening effect on the signal. A clipped waveform
exhibits extreme harmonic distortion, making it sound harsh or
dissonant. The clip limiter detects this and reduces the gain to
minimize the amount of overdrive. To preserve as much of the
program dynamics as possible, limiting reduces the average
program level until peaks barely clip. Each channel has its own
clip limiter, which can be switched on or off. When driving full-
range speakers, clip limiting reduces high frequency distortion
caused by bass overload. It also protects higher frequency
drivers from excess overdrive and harsh clipping harmonics.
Also known as a low-cut filter, a High Pass Filter rolls off signals
below 40Hz. The reproduction of the signal’s bass portion is thus
optimized, since ultra-low, distracting frequencies are
eliminated, and more power is available for the reproduction of
the wanted segment of the signal.
You should set up the filters so they best suit the frequency
response of your speakers, since some speakers are particularly
sensitive to over-excursion. The 40Hz filter works well with most
compact full-range speakers.
Clip limiter HPF (Hi-Pass Filter)
Limiter
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CXA Manual Rev 3_Manual_CXA_English_DB 1/31/2012 10:06 AM Page 4