Is your QSC product generating noise by itself?

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Introduction

Finding the source of noise in an audio system is no easy task. Any audio equipment or cabling can generate noise on its own, including the power amplifier. Noise can come in many forms including humming, buzzing, static, crackling, or ringing. Use the procedures below to determine if the noise is being produced by a QSC amplifier or powered loudspeaker. If the noise is found to be self-generated by the QSC product, then it will need to be serviced. Please read about your service and support options.

 

Basic signal flow of a power amplifier

The most basic setup of a QSC amplifier includes 3 components: a line-level source, power amplifier, and passive loudspeaker.

basicAmpSetup.JPG

 

 

Basic signal flow of a powered loudspeaker

A powered loudspeaker has a built-in amplifier which simplifies the audio system. The most basic setup includes 2 components: a line-level source and powered loudspeaker.

basicPowSpeakSetup.JPG

 

Isolating a QSC product as the source of the noise

In order to determine if the QSC product is the source of the noise, we must isolate it from the audio system. Please follow the instructions below for your specific application.


Amplifiers

  1. Remove all input cables (XLR, 1/4”, barrier strip, euro, or terminal block) from the back of the amplifier. Most QSC amplifiers have the input section on the left side of the amplifier if looking at the back.
  2. Connect the loudspeakers to the output of the amplifier (if not already connected).
  3. Connect the amplifier’s power cord to a known working AC inlet (if not already connected). Turn the power switch to the on position. Verify the amplifier is running and the power LED is illuminated.
  4. Adjust the gain from its lowest setting to the highest. Listen for noise through the loudspeaker. If a moderate to high level of noise is heard, then the amplifier is generating the noise and should be sent in for service.

 

noiseTestAmp.JPG

If no noise is heard, then there is a strong chance that a device or cable upstream from the amplifier is the source of the noise. Reconnect the input cables to the amplifier. To isolate the noisy source, disconnect cables one-by-one from the upstream audio equipment until the noise disappears. If the noisy source cannot be found using this method, try a completely different source and cables, preferably from a known well working audio system.

 

 

Powered loudspeaker

  1. Remove all input and output cables (XLR, 1/4”, or RCA) from the back of the loudspeaker. 
  2. Connect the loudspeaker’s power cord to a known working AC inlet (if not already connected). Turn the power switch to the on position. Verify the loudspeaker is running and the power LED is illuminated.
  3. Adjust the gain from its lowest setting to the highest. Listen for noise. If a moderate to high level of noise is heard through the loudspeakers, then the amplifier is generating the noise and should be sent in for service. 

noiseTestPowSpeak.JPG

A very light static noise may be heard from the loudspeaker if you are listening less than 10 feet from the loudspeaker. This is perfectly normal. If the gain sensitivity or MIC switch is engaged on the powered loudspeaker, noise is likely to be heard from the loudspeaker due to the increased sensitivity.