Troubleshooting - JBL PRX500 User Manual

Noise or hiss heard at output
Hum or Buzz that increases or
decreases when the mixer level
controls are moved.
Hum or Buzz
Speakers feed back and howl when
the microphone volume is turned up
Too much low frequencies when
playing back prerecorded music
32
Noisy Source Device
Improper A/C ground or faulty
equipment connected to
mixer input
Faulty cable between source
equipment and mixer
Improper A/C grounding,
ground loops
Excessively long unbalanced
cable run
Improper system gain
structure
Microphones are pointed into
the speakers
Equalizer settings are
incorrect
Excessive gain
Recorded music with
excessive low frequencies
Disconnect the devices that are connected to
your speaker one at a time. If the noise goes
away, the problem is with the source or the
connecting cable.
Disconnect or mute channels one at a time to
isolate the problem. Refer to the owner's
manual of the faulty equipment for
troubleshooting help.
Substitute a known-good cable for the
suspected faulty cable.
• "Telescope" the audio ground by using an
XLR/F to XLR/M adapter on one end.
• Re-route audio cable away from AC power
and lighting cables.
• Use the balanced outputs (if available) of
your mixer to drive your PRX speakers.
• Use a "DI" (direct injection) box to convert
your unbalanced equipment output to a
balanced output.
Review the Owner's Manual for your system
setup and adjust controls as needed.
• Input sensitivity (gain)
Move the speakers so they do not point to the
microphone's pickup pattern.
Locate the feedback frequency and reduce it
using the mixer EQ or an external equalizer.
Reduce the gain at the mixer and move the
microphone closer to the sound source.
Switch the EQ switch to "flat."