QSC Audio CMX 800V, CMX 300V, CMX 500V Indication Clip LED flashing, Problem Squeals and feedback

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Indication: CLIP LED flashing

If the red CLIP indicator flashes when signal is applied, the amplifier output may be shorted. Check the speaker wiring for stray strands or breaks in the insulation.

Indication: CLIP LEDs bright and steady The amplifier 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 amplifier cools to a safe operating temperature. Check for proper ventilation. If the fan isn’t running at all, the amplifier requires servicing.

Problem: Distorted Sound

Indication: CLIP LED flashing

If the red CLIP indicator flashes before the signal indicator does, the load impedance is abnormally low or shorted. Unplug each speaker one-by-one at the amplifier. 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 flashing

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 amplifier attenuation controls at mid point so that the source does not have to be overdriven.

Problem: No channel separation

Check the switch settings on the back of the amplifier. 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 amplifier input to confirm 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 floor low, operate the primary signal source at full level, without clipping, and avoid boosting the signal further between the source and the amplifier.

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 amplifier, check each device in the signal path by reducing its gain or unplugging it.

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Contents CMX Series CMXImportant Safety Precautions and Explanation of Symbols QSC Audio Products 6-Year Limited Warranty DisclaimerFeatures IntroductionFront Panel Features and setup Back PanelClip Limiter Input Filter Parallel Input Mode Bridge Mono Mode What it isDifference Between Modes Bridge Mono Mode Set Channel 2 dip switches, 8 and 10, to offDistributed Constant Voltage Outputs VoltInstallation Connections InputsSpeakon Outputs Terminal Block Connector Operating Voltage OperationTroubleshooting Fan coolingProblem Distorted Sound Indication Clip LED flashing Problem Squeals and feedbackIndication Clip LED flashing Specifications Facsimile Numbers Mailing AddressTelephone Numbers World Wide Web Mail