# Solve ground loop whine on a boat??



## JonathanEngr (Jul 14, 2014)

Hi, all! I'm new to the forums here, but I have some experience with car audio. 

The only time I've ever experienced whine in my car audio was back in my high school days (mid 80's) when we had "power boosters". You know--those 1000w "amps" that were the size of a wallet. However, not anymore.

I installed a Kenwood D558BT head unit in my pontoon over the weekend, along with a Kicker ZXM700.5 amp, DVC Rockford Fosgate Stage II Punch 15" sub, and four JL audio speakers. I have the Sub running at 2 ohms (the kicker can handle 2 ohm loads on all 5 channels), and the speakers at 4 ohms. The system sounds absolutely incredible and clean--the clarity made me smile from ear-to-ear (I'm no audiophile, but when compared to the factory stereo, well, you know...). 

Okay... I have 2 awg wiring to the battery on the boat. Imagine that you're looking top-down on the boat. The amp is located in a console roughly 4 feet from the back of the boat. The power wiring is running directly from there to the battery at the back, roughly a run of 8 feet of wiring. The head unit is connected to the factory wiring that came with the original stereo (a Pyle, but not sure of model #). 

Obviously, with the engine off, there is no whine. Crank it up, and it whines. Not terrible, but audible. Someone even asked me what the noise was. So... I guess I need to run a new ground for the head unit, as the factory ground was either 16 or 18 gauge wire. But... where do I ground it? Obviously, aluminum is a conductor and I have *tons* of it on the boat (three pontoons, and the entire underbody is lined with aluminum for performance). But is connecting to aluminum a no-no for any reason? I know everyone always says "steel chassis", but there's no steel on the boat at all for obvious reasons.

What about the amp? Does connecting directly to the battery ever create the whining noise? I've always connected my auto amps to the car's chassis to keep the ground short. Should I do the same here connecting tot he aluminum structure? I will definitely start with the head unit as it will be much easier.

Lastly, the engine. My boat has an ETEC 250 H.O. engine, and it has a magneto instead of an alternator. Would this make a difference? I truly have no idea here, although it seems it's just a different way of charging (they used a magneto because they put out many, many more amps versus a standard alternator so you can run more offshore equipment like radios, radar, etc.). 

Any assistance would be greatly appreciated!

Oh... I was proofing my post and wanted to add that the power wiring goes to the back of the boat, and my speaker wires and RCA cables run to the front sections. So--no power/RCA running side-by-side. My RCA cables are 20 feet in length (the head unit has 3 RCA channels.. front, back and sub--I used all 3). I used braided cables for noise rejection on the RCA's. Here are the cables I bought:
T-Spec V12RCA202 20 ft. V12 Series OFC 2-Channel RCA Audio Cable


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## EriCCirE (Apr 14, 2010)

Run wires directly to the negative terminal on the battery! For both the amp and head unit. 

Never connect to aluminum. NEVER!

The generators/alternators on outboards are really weak. If you have you stereo running at full tilt, you will likely kill the little guy. 

Personally, I would use an additional second battery for stereo purposes. That way you can park at the sand bar and keep the tunes jamming, without worry about draining down your starting battery


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## EriCCirE (Apr 14, 2010)

As far as charging goes, you can get an isolator.... I don't have one, and just throw the charger on during the week.

I have a deep cycle in my boat, and the battery lasts multiple weekends without needing a charge.




> Alternator output	133 Amps Total Output/ 50 Amps Net Dedicated


Looks like you have 80 amps to play wth..... With that in mind, I would use an isolator and a second battery.


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## qwertydude (Dec 22, 2008)

Aluminum boats are a toughy. Hopefully as an engineer you can understand the potential corrosion issues with grounding to aluminum. It is possible that you can get galvanic corrosion grounding copper or tin plated lugs to the hull. But it's better to directly ground them and have an all equipotential ground system for your electricals. And of course cover the area with a good dose of dielectric grease to waterproof it.

Then what you have to do is look for your sacrificial anodes and make sure you keep them in good condition, properly connected at all times and cleaned of their corrosion to maximize their sacrificial effect. This is actually just basic boat maintenance really.

With that said, whining is a ground loop. Check the grounds for all the signal paths. The head unit needs to be directly grounded. Get the ground wire and ground it directly to ground as short a distance as possible. Ensure there are no connections in between the ground wire and ground point. That's the number one mistake people make with their grounds, everything is grounded but the connection is a potential series resistance in the head unit and people will swear up and down everything is grounded properly but they still have a connection between the head unit ground because they refuse to cut the head unit ground off the harness. Cut the ground wire directly off the head unit and ground it directly period.

Then go through your other grounds. What you want is the head unit grounded directly to the aluminum hull. Then ground the head unit chassis to ground. Amps of course ground directly to ground and then ground the amp chassis to ground. If this doesn't get rid of it then it's time to get serious about the signal path. You need to get shielded twisted pair wire and make your own RCA's. Microphone cable is good stuff.

Canare L-2T2S - High-Performance - Microphone Cable - Per FT | ShowMeCables.com

Then make your RCA connection and on each end expose as little extraneous wire as possible from the shielding. And then at each end ground the shielding with as short a wire to ground as possible.

This is pretty much the FAA spec for grounding electronics to prevent interference. I learned about it as an avionics tech a while back. This method has never failed to get rid of the most stubborn of ground loops, noise, and interference. When people swear up and down they've done everything they can to get rid of noise I ask them if they wired their system up like above, and obviously they didn't, when they do, noise is gone. Guaranteed.


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## JonathanEngr (Jul 14, 2014)

Thanks for all of the replies. QwertyDude--I do understand the possibility of corrosion connecting to aluminum, and that would be something I'll have to deal with. My boat is not set up for saltwater use, so there are no sacrificial anodes, etc., on the boat. 

Okay--so there are two differing opinions. One to never connect to aluminum, and one to connect to it several times. As I'm not an electrical engineer (I'm a Civil), I would need to seek out the absolutes on aluminum. EriCCire--is this an absolute rule of some sort, or is it a personal preference? Obviously, my options are limited.

As for running the ground to the battery, I can do that. However, it will be about a 15-foot run. I've always been told to keep the ground as short as possible. I've never noticed this before, but do you have to have a ground wire running from the battery to the chassis in all vehicles? I didn't know if that was a requirement. If so, I could trace the wires coming from the ground side of the battery to see if an connect to the boat, and if so, where.

EriCCire--you are correct on charging. Even the big engines (200+ HP) are small on charging. Most outboards have a TOTAL output of 50 amps, but the ETEC has 50 amps just for the battery, and 133 total. It kind-of sets it apart. I thought that was actually pretty good since most car alternators range between 60 and 100 amps at around 14v--correct? I do have an A-B battery switch for boats, and I even have a dual cradle for two batteries--I just never installed it. I bought it for this reason, however. Not so much to always run the stereo from the battery NOT connected to the engine, but to have a second backup battery in case I run the main battery down playing music without the engine running. My main concern is discharging the battery too much. Even deep cycles have their limits. How much exactly can you safely discharge a 12V deep cycle battery over and over without damaging it? I guess I could always put a voltmeter in my dash to keep an eye on it.

EDIT-----

Here is the battery switch I purchased about two years ago. I haven't installed it, but I need to...

http://www.amazon.com/Blue-Sea-Syst...5361365&sr=8-1&keywords=marine+battery+switch


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## qwertydude (Dec 22, 2008)

Well I'm betting there is ground somewhere connecting battery negative to the aluminum hull. The reason being is outboards themselves usually have the alternators connected to ground and have their own separate sacrificial anodes. This means when the outboard is bolted to the hull if any of those bolts touch aluminum you've got a possible potential difference because of the copper negative lead and the grounded outboard chassis. Then the smart thing to do is run a proper grounding system.

Get a DMM and measure the resistance from the battery terminal to the aluminum hull, make sure where you measure you press hard enough to get a measurement. Usually the anodizing can fool you. Scratch a little of the anodizing off and make sure you can get a reading from aluminum to aluminum. Then measure from battery negative to aluminum. If there's no connection then it might be better to extend the negative cable from the negative buss long enough, probably with 8 gauge or better copper wire, to the head unit and ground to that wire. But if you do have a connection you've already got an electric potential set up and your best bet is to minimize the potential difference by thoroughly grounding so there's minimal potential difference across the various ground points.

Boat grounding questions - www.ifish.net

Here's a relavent discussion. So measure your hull, if the battery negative truly is isolated, don't connect it to the hull. If you've already got a negative to hull connection, minimize the possible ground potential and differences by proper grounding. Better to have everything be equipotential than to end up creating a natural voltage difference across different parts of the hull due to poor grounding efforts.


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## JonathanEngr (Jul 14, 2014)

> Get a DMM and measure the resistance from the battery terminal to the aluminum hull, make sure where you measure you press hard enough to get a measurement. Usually the anodizing can fool you. Scratch a little of the anodizing off and make sure you can get a reading from aluminum to aluminum.


You state above to use the DMM to get a resistance from the battery to the aluminum hull, then you say to make sure I get a reading from aluminum to aluminum. Do you mean to compare the resistance from the negative battery terminal to the hull, and be sure to scratch off the anodizing on the hull enough to get a reading from the battery to the aluminum? Or do you mean go from the positive terminal to the hull and then from the negative terminal to the hull (below)? Any idea to what scale the resistance should be? Again, electronics aren't my forte.



> Then measure from battery negative to aluminum.


This is where I am confused. You mentioned in the section above to test from the battery to the aluminum.... this is why I wondered if you meant to test the positive to the hull, and then the negative to the hull. Can you go over again what I should test with the DMM? 



> If there's no connection then it might be better to extend the negative cable from the negative buss long enough, probably with 8 gauge or better copper wire, to the head unit and ground to that wire. But if you do have a connection you've already got an electric potential set up and your best bet is to minimize the potential difference by thoroughly grounding so there's minimal potential difference across the various ground points.


So by "negative bus" you mean the panel under the dash that has several wire and fuses connecting to it? I do think there is a panel under the captain's console, but I will need to check.

I did look at the link on grounding with yachts, but that system is vastly more complicated. If you could simplify the DMM testing I need to do (what battery terminal to the hull, hull to hull...?, etc.) I think I can knock this out. Thanks!


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## qwertydude (Dec 22, 2008)

Measuring from aluminum to aluminum just guarantees you have a proper reading. If you can't measure 0.0 ohms from aluminum to aluminum then your battery negative to aluminum can possibly fool you into thinking the aluminum is isolated. That's why you want to first measure from aluminum to aluminum. The only test you care about is the battery negative to the aluminum hull but the aluminum hull to aluminum hull is just a sanity check to ensure you're measuring properly.

Several wires and fuses under the dash is not the ground bus. That's the fuse box. The ground bus if there is one is usually closer to the battery and will be directly connected to the negative battery lead, so follow the negative lead and wherever you see a bunch of negative wires connecting together to the negative battery lead that's the bus. It's also not necessarily a rectangular bar, the bus could very well just be a brass or chrome plated brass bolt with a nut holding down a bunch of terminals. That is unless the boat was designed with everything grounded to the aluminum hull, then you simply won't find one. In this case you should have been able to measure 0.0 ohms and proceed with the grounding procedure I described before.

Boat or yacht, corrosion doesn't care. It'll rot both vessels just as easily. When I was in the navy the aluminum patrol boats had the same exact corrosion setup as the aircraft carriers, only smaller. So you can't just assume your boat being small is different, it's not. It's a metal boat in the water.


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## Open Water (Jan 20, 2009)

Nothing is worse than running out of juice at the end of the day. Dedicate a battery for starting and charge both when underway. 

In all my boats I run ground straight to the battery. I also use a perko switch / isolator with a second battery (off/1/2/all).


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## JonathanEngr (Jul 14, 2014)

Qwertydude: I probably didn't explain myself well. I do understand that corrosion will happen on any similar material in a particular environment despite the size of the object. I was referring more to the discussion about the different types of wiring for the different AC and DC systems and the different types thereof. I just have a little 12V system on a pontoon... I don't want to be any further confused! LOL! 

You latest post now makes complete sense. I'm just going to test for continuity between the battery ground and the structure to make sure there is no connection there. I just didn't follow in your first post.

Open Water--I couldn't agree more. I continually hop on the boat just to run the engine for a few mins, and during the power break while cranking I have to reset my input, start the music stream and reset the volume. It would be nice to just kick back, enjoy the music and know for certain that I have a second untouched battery there ready to crank when needed. *Especially* now that I'm running quite a few more amps. Regarding my dual battery switch, did you see the type of switch I own from an earlier post? I've had it for 2 years now but just haven't installed it. I wonder if you use the same one...

http://www.amazon.com/exec/obidos/ASIN/B000K2MCR2/ref=nosim/diymacom-20

I might have a question or two when it comes to installation.


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## Open Water (Jan 20, 2009)

JonathanEngr said:


> I wonder if you use the same one...
> 
> http://www.amazon.com/exec/obidos/ASIN/B000K2MCR2/ref=nosim/diymacom-20
> 
> I might have a question or two when it comes to installation.



Yes, I use a similar part. The brand is Perko - very common in boating and often just referred to as a Perko switch. 

It's a lot less stress to be able to isolate your batteries. I'll typically run both, but if we're beached for awhile I go ahead and isolate my staring battery. Then charge it up when out running again. You already got the switch, pick up an extra battery and battery box and be done. 

If you tender in harbor or store in a channel (eg. with houses), keep up on your zincs; otherwise, it will likely be negligible if just "day boating" here and there. 

-JT


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## Open Water (Jan 20, 2009)

Double post


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