QSC CMX 300V User Manual page 18

Indication: CLIP LED fl ashing
If the red CLIP indicator fl ashes when signal is applied, the amplifi er output may be
shorted. Check the speaker wiring for stray strands or breaks in the insulation.
Indication: CLIP LEDs bright and steady
The amplifi er is in protective muting.
One second of muting is normal when the amp is turned on or off.
Overheating will cause protective muting. The fan will be running at full speed and the
chassis will be hot to the touch; sound should resume within a minute as the amplifi er
cools to a safe operating temperature. Check for proper ventilation. If the fan isn't running
at all, the amplifi er requires servicing.
Problem: Distorted Sound
Indication: CLIP LED fl ashing
If the red CLIP indicator fl ashes before the signal indicator does, the load impedance is
abnormally low or shorted. Unplug each speaker one-by-one at the amplifi er. If the CLIP
LED goes out when you disconnect a cable, that cable or speaker is shorted. Try another
cable and speaker to locate the fault.
Indication: CLIP LED not fl ashing
This could be caused by a faulty speaker or loose connection. Check the wiring and try
another speaker.
The signal source may be clipping. Keep the amplifi er attenuation controls at mid point so
that the source does not have to be overdriven.
ENG
Problem: No channel separation
Check the switch settings on the back of the amplifi er. Make sure the "Parallel Input" and
"Bridge Mode" switches are OFF in dual-channel, bi-amp, or stereo use where different
signals go to each channel.
Make sure other equipment in the signal path, such as mixers, preamps, etc., are set for
stereo, not mono.
Problem: Hum
Move cabling and signal sources to identify "hot spots" in the system. Cables with faulty
shielding are a frequent entry point for hum.
Problem: Hiss
Unplug the amplifi er input to confi rm that the hiss is coming from the source or a device
upstream; erratic or popping noises indicate an electronic fault in the offending unit.
To keep the normal noise fl oor low, operate the primary signal source at full level, without
clipping, and avoid boosting the signal further between the source and the amplifi er.
Problem: Squeals and feedback
Microphone feedback should be controlled with mixer controls. If noise continues to build
up with zero mic gain, there is a serious fault in the signal processors or cables. Working
in succession from the signal source towards the amplifi er, check each device in the signal
path by reducing its gain or unplugging it.
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