OMF Posted July 2, 2015 Share Posted July 2, 2015 I have stereo speakers of two rooms connected to a rack mounted C4 4 zone amp (C4-AMP104), inputs coming off of a C4 16 channel audio matrix (C4-16ZAMSV3). There is a distinct white noise hiss in both rooms’ speakers when the C4 4 zone amp is OFF (i.e. power on, but nothing selected [Room Off] and no indication of any “zone on” status on the amp’s front panel). Adjusted the individual zone’s sensitivity settings, but could not eliminate the white noise.Any suggestion? Link to comment Share on other sites More sharing options...
Matt Lowe Posted July 2, 2015 Share Posted July 2, 2015 bad grounding would be one place to look Link to comment Share on other sites More sharing options...
OMF Posted July 2, 2015 Author Share Posted July 2, 2015 bad grounding would be one place to lookThanks for your quick reply. Although the hissing sound from a turned off output did not sound a grounding issue, I have double and triple checked everything, the grounding of the entire rack, reconfigured the power supply {UPS --> Panamax M5300-PM power conditioner}, connected the Amp and the Audio Matrix to plugs on separate circuits, nothing has changed. If I turn off the amp with its On-Off switch, the hissing sound stops. Link to comment Share on other sites More sharing options...
SMHarman Posted July 2, 2015 Share Posted July 2, 2015 If you disconnect sources does the hissing stop? Link to comment Share on other sites More sharing options...
OMF Posted July 2, 2015 Author Share Posted July 2, 2015 If you disconnect sources does the hissing stop?Excellent question, unfortunately the hissing sound does NOT stop after disconnecting the input. Link to comment Share on other sites More sharing options...
Kalschjj29 Posted July 2, 2015 Share Posted July 2, 2015 Could try lifting the ground using a ground lift plug. Not my recommended fix but as a troubleshooting step. Link to comment Share on other sites More sharing options...
OMF Posted July 3, 2015 Author Share Posted July 3, 2015 Could try lifting the ground using a ground lift plug. Not my recommended fix but as a troubleshooting step.Unfortunately it didn't help. Any other suggestion? You can look at the problem like this: We have a standalone 4 Zone Amp connected to speakers, all zones off, all inputs disconnected, and you can still hear the white noise from the speakers... Link to comment Share on other sites More sharing options...
Kalschjj29 Posted July 3, 2015 Share Posted July 3, 2015 If you have a multi meter you could test the speakers impedance. This is more of a troubleshooting to see if it could be the speaker. The C4 amp can handle between 4-8 ohm. If measuring you get 2 ohms this could cause damage to the amp over time. You could also try connecting some bookshelf speakers to the amp to verify the white noise is still there, if so the speakers are likely not the issue. Just to confirm, if the amp is powered on alone and the C4 matrix is powered off you hear the noise? Link to comment Share on other sites More sharing options...
SMHarman Posted July 3, 2015 Share Posted July 3, 2015 What make and model are the speakers? Link to comment Share on other sites More sharing options...
OMF Posted July 3, 2015 Author Share Posted July 3, 2015 Tanks for your replies Kalschjj29 and SMHarman Speakers in one of the rooms: Monitor Audio Pro IC 65 2-way in-ceiling speakers. Impedance 6 Ohms.In the other room: JBL Control One AW 2-way speakers (kind of a bookshelf type). Impedance 8 Ohms. And yes, if nothing else is powered in the rack just the amp, with all inputs disconnected, I can still hear the white noise from the speakers of both zones. It is like a very quiet hissing noise, like the amp was set on at its lowest volume, frequency is higher than the typical 60Hz. I wouldn't bother if the in-ceiling speakers were not in one of the bedrooms, so on a quiet night it becomes audible. Link to comment Share on other sites More sharing options...
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