Speaker hum from cockpit speakers

[Tugbuyer]

I have a Fusion AV600 with a AM702 zone amplifier to power a 3rd zone in the cockpit. I also have a wired remote for the 2 main channel speakers (forward stateroom & cabin), a BT100 Bluetooth module, and a 2nd wired remote installed to control the 3rd zone (cockpit) speakers. All works as intended, however the 3rd zone has a pretty loud hum when the system is on, regardless of sound source. It seems to be only the 3rd zone that's affected and is more pronounced at low volume, but always annoying. I'm assuming the problem is caused by or associated with the zone amp, but not sure why or how to fix (short of replacing it). Any ideas? (2011 Ranger R29)

 

[Pilotnavigator]

Everything grounded and wire runs a good distance from other electronic data lines?

 

[Tugbuyer]

Yes, all grounds are good. Today I was able to minimize the hum considerably by playing with/adjusting the "frequency" and "level" controls. It's still there, but not nearly as bad.

 

[Mystical]

We had been battling the same problem since we bought the boat. After a few people had looked at it and never finding a cause, I decided to poke around myself. I had found that our problem was more prevalent when on shore power. I took the stereo memory wire off of the house battery switch and moved it to the thruster battery switch. Since then, our problem of the humming is gone

 

[Pilotnavigator]

Also check that there are no transformer type devices near the radio or the speaker lines. Is the HUM a 60 cycle noise? 12 volt USB adapters, have a small transformer, fridge ? etc. Turn off as much gear as possible, even turn off the batteries (disconect shore power - big transformer in there) and run a second line to the radio direct from the battery or use a jump start battery and connect direct to that. If the hum is present then you have a problem within the radio system. IF all is good then work forward from there, turn back on one system at a time. Adjusting the radio to reduce the hum is not a cure.

 

[Irish Mist]

I get a hum when the light over the table is on. Has to do with the dimmer I'm sure.

 

[ozoner]

Does the hum vary with engine speed? Another common place for this to come from is the alternator, and if so the hum will change with the speed the alternator is rotating

 

[Tugbuyer]

Hum is present with engine off, so alternator as source is out. Also, to clarify, I adjusted "frequency" and "level" controls on the amplifier unit (not the radio), and this appears to have reduced the hum to a very low level, barely detectable by me, but probably not to others. I am considering this "case closed" and moving on to other issues (there seems to always be one...). Thanks to all for the support/feedback.

Dan

 

[Ard]

This problem could be caused by a ground loop. A ground loop isolator such as this http://www.amazon.com/Audio-B25N-Gr...13993523&sr=1-2&keywords=ground+loop+isolator may be a solution. Insert it at the signal (RCA) cables feeding the zone 3 amplifier.

 

[Automaticman865]

One thing to look at is if on the house batteries and the overhead lights and they are LEDs , and you get hum, it could be the voltage regulators putting all that noise on the line. If you hot the older bulbsb swap em out and try again

Stuart