Whine on surround sound system

[UK_Steve]

Hi Guys,

Any help much appreciated…

07 Monaco Cayman 36PDQ.

Has a surround sound system , five speakers in the roof, a line of three at the front and two the rear of the main area. There is a whine from the rear two speakers, low key but there, and very obvious when the radio is turned off but there is still power the stereo and power amplifier. Anyone had and resolved this yet? It sounds like an earth noise.

Many thanks

[RJay]

What your experiencing I think is 60 cycle hum. Some how the AC frequency is mixing with the audio frequency which could be caused by a poor ground or a shielding issue. It could also be caused by a bad starter on a florescent light but I don't think that's the problem in this case. One way to check it is to set the frequency on a portable radio to a non used station about 600kHz and move it around your equipment, where the hum is the loudest is the general proximity to the problem.

[UK_Steve]

Hi RJay,

I did wonder if it is 50Hz induced (we have 50 in the UK) from a bad ground/earth somewhere, I like the idea with the portable radio, will give that a go over the weekend. Can rule out the strip lights as should have said get it any time not just at night time. Another idea is to unplug the shore lead and see if it goes away, so I think it’s a combination of portable radio with shore lead connected and disconnected and trace.

Many thanks

[OKDynasty]

UK_Steve, Greeting! My surround sound will do that if the lights (halogen) that are over the couches and controled by adjustable rheostats (dimmers) are on. The rheostats seem to be the culprit in my coach. Might give it a try if you have / use them also. Happy travels......

[wa8yxm]

If you are running on an inverter.. Non True Sine Wave (MSW) inverters are well known for adding a tone to the audio system. As OKD said, Dimmers (NOT Rheostats but SCR or Diac type Dimmers which are something else) will do it,, A true Rheostat will not.. just so you know.. but those are big, get very hot and are not common any more ... Even in newer theaters.. You still find them in older theaters. (One of my many "Talents" Theatrical lighting operator, Sounds much more impressive than it is, fancy name which means "I know how to turn the lights on and off")

Anything that "Chops" power, some motor speed controls, some other stuff, can do it.

And I've seen alternator whine make it past an inverter too.. rare but it happens.

[JimM68]

It is a grounding issue, well known and with a real fix. Not the inverter. not the lights. I've read the answer here, but have forgetten as my coach don't got the problem. A search will turn it up.

[UK_Steve]

Hi JimM,

Found the thread, it is here if anyone wants’ it http://www.irv2.com/forums/f115/surround-sound-system-sounds-great-now-43086.html lots of good stuff, in nut shell the author installed a "Ground Loop Isolator", (Pyramid 15 Amp High Quality Noise Suppressor Isolation Transformer NS-20) and balanced out the volume pots on the amplifier, need to hunt down a "Ground Loop Isolator now.

Thank you very much for your help on this one.

[SailDJ]

I turned off the speaker switches located in the cabinet with the router that changes from DVD, Cable, Sat or Ant, and the noise went away.

[UK_Steve]

Well in the process of pulling cables out and tracing the cabling for the digital satellite (another question on this forum from me) I found an inline “Pyramid High Quality Noise Suppressor Isolation Unit” behind the back of the AV cupboard (physically behind the back wall of the cupboard) above the drivers seat, but the output was strapped to all the other wiring, hence the noise induction! Unstrapped it move the amplifier feed wires away from the rest, trimmed the amplifier pots as per the recommendation in the link I found and Good Perfect quality sound.

Thank you to every one for your help and recommendations.

[trouble&rose]

add a ground loop isolator for about $25 dollars and check for needed adapter plugs to put new noise suppressor at input plugs for sound (red & white plugs)

our hum is gone and i am adding 4 new white pioneer marine speakers to improve sound quality

good luck

Trouble

[trouble&rose]

radio shack has all you need to fix for about $30

[UK_Steve]

Hi all, quick update, all sounded great the other day, was left powered up but the stereo off for a few hours and the hum is back, so maybe what I found did not completely clear it. So back to the installation of a Quality Noise Suppressor Isolation Transformer etc. Thanks for all the pointers and help.