Electronics/Stereo Noise Interference Help Needed

[Bust it Big]

I recently installed a 5 Channel amplifier to my JBL Head unit. The amp is hooked thru the JBL's RCA hookups using Gound Loop Isolators on each channel. I also have XM thru the Garmin 3210 Bundle with the XM receiver installed in the overhead box and connected with "better than average" RCA cables to the head unit's external RCA input which is installed in the cabin (the RCA's are approx. 10 feet and not twisted cable).

The problem is I am having interference problems when listening to the XM Input. Initially, I had 8 Guage running direct to backup battery (12 ft) and the 8 guage ground to ground block (2 foot) under the helm. Under this setup, there was a low pronounced hum when the XM was on. There was also a higher pitch (but too loud) interference that paralleled the engine when under way. Next I tried using 8 Guage ground direct to the battery negative terminal ( 12 ft). I don't seem to hear the same interference when engine is running but still have a really low hum. Have to listen for it but it's there. Also, I get a loud (as loud as volume is) sound when I adjust the engine tilt. Haven't been on water to hear any other possible interference issues yet.

Any takers on what I can do to eliminate or at least reduce the inteference??? :cry:

 

[NOTHING ELSE MATTERS]

Sounds like your RCA cables are very close or bunched with wires that carry voltage or RF signal. Try to isolate or run them far from the boats electrical wires. #1 cause of your problem usualy is the ground, but you already checked that(moved it).

 

[seasick]

Hard to say but one thing to check is cable routing. If the signal wires are wrapped in the same bundle as the power cables, try separating them. In addition, avoid long parallel runs of power and signal. That may be more difficult than it sounds since you may only have limited ways to run cables.
I also wonder if the isolated ground cables have created a non-grounded floating antenna but I am not sure.
If you can determine if the noise is introduced in the power wires or the signal wires, it may help. Usually the signal wires will respond to routing changes. The power may be more of a challenge.

 

[Bust it Big]

Thanks. I have the power/ground separated from the signal with both running solo down one of the access tubes in hull to battery. Can the previous post verify what is meant be the isolated grounding cables and floating antenna.

 

[BobP]

So where is noise coming from power or RF?

Is ALL your electronics single point grounded?
Is the XM antenna gounded and cable leading to it propley connected or is shiled floatimg?
Check motor internal grounds for corrosion.

While the noise is occuring crank up volume, and go around tugging on wires, in transom and motor too.

See if noise changes, if it does, you found it.

You seem to be picking up motor noises, so I'd check the motor grounds and the grounds on your electronics. Stick to single point grounds.
Either one or both is doing it.

Today's electronics are well protected against causing interference as well as picking up interference, as it comes straight out of the factory box.

 

[seasick]

BobP has good advice, especially about looking for bad grounds on the engine /battery connections.
You said you used ground fault isolating RCA cables. I am not sure what that is but it sounds like you won't have a continuous ground connection. If so and if the interference is RF, that 'isolated' circuit could act as an antenna.

 

[Bust it Big]

I tried using a Ground Loop Isolator on the RCA output of the Garmin XM receiver to the JBL Headunit while leaving the ground direct on battery and it solved the problem. No more noise! In fact, I was feeling so good about finally getting it right, I re-wired the GPS and was able to get that working as well! :lol:

Thanks to all who provided advice, I kind of took it all in and was prepared to work thru the suggestions until it was working interference-free.

 

[seasick]

I tried using a Ground Loop Isolator on the RCA output of the Garmin XM receiver to the JBL Headunit while leaving the ground direct on battery and it solved the problem. No more noise! In fact, I was feeling so good about finally getting it right, I re-wired the GPS and was able to get that working as well! :lol:

Thanks to all who provided advice, I kind of took it all in and was prepared to work thru the suggestions until it was working interference-free.

That's great. Enjoy.

 

[BobP]

I like it when a plan comes together!

Single point grounds are the opposite of loop grounds.
Loop grounds are trouble but cheap and fast to make up, that's whey they are done, other than for the usual human (ignorance) factor.