Stereo noise issues

[h20boy22]

I have a Supra 21V and still have noise issues in my sound system. I have a MB Quart head unit with 2 amps. One amp is running in boat speakers and sub. The other is a Wetsounds amp running 2 Rev10s on the tower. When I pause the music or listen to it at a low volume I hear a "static" type white noise that is very annoying (regardless of whether boat is running or not). I have read about running the power from my head unit directly to the battery or amp. Is that what I should do? The noise is in both the in boat speakers and tower speakers. Right now it runs to a switch on the drivers panel so I can turn the stereo off with that switch. I hate to lose this functionality but will do so if needed. Right now the gain on the Wetsounds amp is turned down to about 35% or less to help reduce the noise but this makes it hard to hear the speakers when boarding. Please help if you can!!! I am not an audio guy but am handy enough to follow logical directions.

[MLA]

H20,

Since the noise is present on all the speakers, its safe to say its generated at the source and feeding both amp. Is it present with the tuner and CDs as well?

Yes, by all means, the head-unit needs to have its yellow B+/MEM and black GND need to be terminated to the same battery source as the amps. Good news is, this will not effect how you are turning on your head-unit currently with the switch on the dash. This function is actually done by a small red wire on the head-unit that is fed B+ through that switch.

So, by your post, im gathering your boat only has a single battery. If so, then I would not rewire anything just yet as the whole system has no choice but to share the same battery. I would inspect the RCA cables connections real close. A loose RCA can induce some static type noise. Next, I would inspect the B+ and GND connections and any crimps/splices along thier path. If any are suspicious, then just rerun them directly to one of your amps. I did this same thing today on a Baja that had a head-unit powering down while the boat was under way. The feed came from the transom off the battery, and had 3 splices within a foot of the head-unit. Cut them all out and went directly to the tower amp that was 18" away and fed by 4ga cabling.

One means of isolating the issue is to take a 3.5mm headphone jack x RCA and go directly from your MP3 to each amp. If the problem goes away, then you know its upstream on the source signal.

[KSmith]

One means of isolating the issue is to take a 3.5mm headphone jack x RCA and go directly from your MP3 to each amp. If the problem goes away, then you know its upstream on the source signal.

^^^ Great troubleshooting approach right there!

[h20boy22]

I do have two batteries and all amps and the stereo are feeding off the same battery. I have confirmed the noise is present on both the aux in and cd source. I have also connected my MP3 directly to amps via RCAs and the noise went away. This means it is something between the head unit and amps, correct? The problem is I can't figure out what to check/change next. The head unit is grounded directly to one of the amps.

[MLA]

I do have two batteries and all amps and the stereo are feeding off the same battery. I have confirmed the noise is present on both the aux in and cd source. I have also connected my MP3 directly to amps via RCAs and the noise went away. This means it is something between the head unit and amps, correct? The problem is I can't figure out what to check/change next. The head unit is grounded directly to one of the amps.

Ok, so the noise is present through both amp and each amp is fed by is own RCA cable from different outputs on the head-unit. Just about narrows it down to the head-unit. Try disconnecting the RCA from each amp one at a time and see if the noise is still present through the other amp. Next would be to trying another set of RCA cables just laid across from the head-unit to the amps.

[h20boy22]

I have tried the amps independently with same results. Haven't tried a different RCA cable but I can try that. Anything else? Thanks for the help.

[h20boy22]

Okay I have tried different RCAs and even switched front and rear RCAs and the noise continues through all speakers. This points to the noise coming from the head unit. So my question is how can I determine whether the head unit is just not grounded well (visual inspection looks fine) or there is something in the head unit causing the noise and the head unit needs to be replaced? This boat is a 2011 so it is not like the head unit is old.

[MLA]

Try taking the head-units yellow MEM and black GND off the boat's harness and run a new pair directly to one of the amps. You may also look to see if the head-unit GND is connected to the head-unit chassis as well.

[h20boy22]

The yellow wire is still connected to the boat's wiring harness but the ground wire is running directly from the head unit to one of the amps. From what I can see the head unit ground wire looks connected securely at both ends.

[Brianinpdx]

h20 - do you have an eq in this system? and if so, which one?

-Brian
Exile Audio

[h20boy22]

No eq in the system. Signal goes straight from head unit to amps.

[dusty2221]

Not to hijack, but since the topic was brought up. Regarding moving the B+ Yellow from the H/U to the same battery the amps pull power from - Does this have to all be the SAME battery in the stereo bank, or lets say if there are multiple batts in the stereo bank just make sure and go to the stereo bank vs. how it comes from the factory?

In my case, I need to make this last wire move pretty much just so everything is completely stereo bank dependent, and I have a battery in the stereo bank that takes about 1/4 of the work to get a wire to, except every other + and - related to the audio goes to the other batts on the stereo side.