Identifying Electrical Grounds

[samahickman]

Morning! I’ve got engine whine in stereo and checking to be sure engine ground is on separate battery from stereo/amp grounds. Any guesses on how I’d tell which ground is for which systems? Here are pics of my 2 batteries as they sit today. Thanks guys!

 

https://www.dropbox.com/sh/iv602746kvevoln/AADWhWlgIvsSgzO-ZefrOPrua?dl=0

[MLA]

12 minutes ago, samahickman said:

checking to be sure engine ground is on separate battery from stereo/amp grounds

This cannot take place. Boats have a single, common ground point, and thats the engine block. If you remove the house bank's ground from the rest of the boat, then your house bank becomes 100% isolated and stand-alone, and will eventually go dead. 

Think about jumper cables have two cables, one for the + and one for the - at both ends. Why? because it take both to complete the circuit. You will never jump start the dead car by simply connecting the the positive clamps. You must have the ground. 

In 99% of cases, engine why is not a "ground" problems. Its a voltage difference between the audio components. But why doe so many say "check your grounds? Because the term often used to describe engine whine, is Ground Loop. Ground Loop has little to do with the ground side of the DC audio components. If there is poor DC ground connection, the component will likely not power up, or will intermittently power down when under load. The nasty noise you hear with ground loop, it the voltage difference equalizing through the ground side of the RCA cables. 

 

The other likely, bur rare, cause of engine noise, is a failing alternator, leaking AC into the DC output.  

[samahickman]

Whoa! Thank you so much, MLA. I really appreciate the help. I was thinking I needed my stereo/amp grounds isolated to one battery and everything else grounded on another battery. Sounds like that’s not the case.

If my problem is a voltage difference, equalizing through the ground side of my RCA cables, any ideas on how to validate that or correct it? Thanks again!

[Steve B.]

Any quick tips on isolating engine noise in our sound systems MLA ? I have it too. Based on your above post, in my case I'm wondering if removing the RCA inputs to one of the amps would be the first step? I've got a two amplifier system and after replacing one of them, I have the whine.

Thanks !

 

[samahickman]

Hey Steve-Glad to know I'm not alone. I've got 2-RF Amps (1 for Sub and 1 for Cabin) and 1-JL Amp (for Tower). Whine comes from all speakers when boat is running. It improves if I turn down all gains (still noticeable tho), but gets way worse when I turn gains up. I am thinking the ground location on the Rockford Black Box may need adjusting? I just bought the boat and was told the JL amp got added recently (along w/replacing all tower speakers), so maybe that's a consideration as well? Hoping MLA has tips. It drives me crazy. I might just buy a couple of those ground loop isolators? A) maybe that'd fix my problem and B) if it did fix problem, I'd know what problem was!

[MLA]

So in both these cases, there is new and/or non-OEM amps. With the RCA removed at the amps, if the noise is gone, then its coming in upstream. With the RCA plugged back into the amp(s), then disconnected at the media unit, the noise should still be gone. If it comes back, then its bleeding into an RCA some where along the routing. This is rare in mobile 12V DC, but there are some electronics, like a depth finder, that can induce noise into the signal path. 

On a 2014, Malibu would have likely terminated the BB's 12V and ground, to one of the amps' power terminals. This is about as good as it gets, for the all the equipment so "see" the same voltage source. Let me stress again, dont put all your focus on the component's DC grounds. As I stated, ALL the ground are common at the end of the day. However, in a boat with a 2-bank setup, there are two sources for 12V B+. In almost all cases, this is where ground loop is resolved.

GLI's are just a bandaid. 

In a case of an older boat and a new amp, id try a new pair of RCA. As a test, just drop them from head to the amp. Right across the boat. Dont fully install.  

[Steve B.]

Awesome. Those sound like the quickest ways to determine the source of the issues.

Thank you.

[samahickman]

Thanks, MLA! Just went and troubleshot. Confirmed that, with the RCA cables disconnected from the amps, the noise disappeared. I feel like an idiot because, I cannot figure out how to kill power to the media unit to test that scenario. There's a Rockford display in the dash, w/single hard line out to the Black Box, which is in the battery compartment. For the life of me, can't find a good way to cut power to that black box! Pic below (Rockford Black Box upper left on board.)

https://www.dropbox.com/sh/iv602746kvevoln/AADWhWlgIvsSgzO-ZefrOPrua?dl=0

[justgary]

An RCA shorting plug can also be useful to help isolate the problem.  Move it from one input (*not* output) to the next to find the worst offending input.  When you find it, carefully inspect the situation at that input, including the RCA cables involved.  As @MLA mentioned, using a temporary jumper RCA from the head unit to that input can also help find the problem.

[samahickman]

Thanks JustGary!

 

[samahickman]

Hey Guys-Have some updates to share. Curious to hear your initial reactions. 

Issue: With amp gain at 0, faint static/ringing coming from cabin and tower speakers that gets louder as gain is increased. Only present when engine is running. If not running, no static/ringing.

Why this is a problem: With zero amp gain, music needs to be dialed up high on head unit (HU) to hear. Leaving a lot of power on table.

Setup:

• 2014 VLX, Rockford Fosgate RFX5000, 2 - RF Amps (1-driving sub, 1-driving cabin), 1 - JL Amp (driving tower)
• Prior owner replaced RF Amp driving tower w/JL Amp.

Scenarios Tested:

• Disconnected RCAs from amps - Fixed (so problem is upstream from Amps)
• Cycled different inputs on Head Unit (Aux Line-in/BT/USB) - No Change
• Checked/tightened all connections (RCA, USB, etc.) - No Change
• Ran RCA direct from Black Box (BB) to Amps - No Change
• New battery terminals - No Change
• Disconnected/reconnected power on newly installed JL amp - No Change
• Installed Ground Loop Isolators on both Cabin and Tower amps - No Change
• Disconnected Malibu Bluetooth module - No Change

Conclusion: Seems like problem is with the Head Unit; however, it doesn't make sense to me that the problem only exists when the engine is running. Thoughts?

[samahickman]

Update: I ended up calling a local marine stereo install shop in Minneapolis (where I’m located). Their take was that I just have my gain settings to high. They primarily do JL installs and said that 99% of them have gain settings at the 9 o’clock position (whereas mine were at the 3’oclock position). Will give it a go!

[Brandonloos21]

38 minutes ago, samahickman said:

Update: I ended up calling a local marine stereo install shop in Minneapolis (where I’m located). Their take was that I just have my gain settings to high. They primarily do JL installs and said that 99% of them have gain settings at the 9 o’clock position (whereas mine were at the 3’oclock position). Will give it a go!

Okay I wouldn’t jump to this as being your solution. Gain setting is not a “level” knob, it’s an input sensitivity match. Meaning that it’s matching the amp to accept the level of signal your headunit is CAPABLE of putting out. 
 

They might only have their amps at 9 o clock because they’re using headunits with “hotter” preouts than the stock units (which I have found to suck). 
 

If you have this noise ONLY when the engine is on, it’s not a gain problem. All you’re going to do is turn your amps input sensitivity down, making it less noticeable, and your music will be more quiet, though it will still be there. They might think you are talking about white noise. As amps input sensitivity is turned up, more hiss is introduced into the system, and is translated really well by efficient speakers, such as wetsounds horns. This is why a lot of people opt for headunits with hotter preouts so they can mitigate this white noise/hiss. 

[samahickman]

Thanks, Brandon! Those are fantastic points! Although they leave me stumped. I’m not sure what else to check in terms of noise introduction. But I suppose if, when I run jumper RCAs direct from BB to amps, I still get the noise, the problem must be with my old RF stock unit? Is that what you’re inferring?

I’m thinking my problem is not typical engine whine, since it doesn’t change with RPMs and the ground loop isolators I installed didn’t change anything.

I also thought I should try put all the non stereo grounds on one battery and have stereo grounds by themselves on a battery. (Right now all my accessory grounds like stereo, bilge, etc. terminate on one battery’s negative terminal.) I don’t think there’s any risk to shuffling those grounds around, right?

another thought I had today, maybe I’ll try turning off the Malibu auto volume adjustment feature (that changes vol levels automatically depending on how loud engine is). Appreciate you jumping in!

 

Edited June 21, 2023 by samahickman

[Brandonloos21]

No problem. One solution might be to try grounded RCAs. Maybe try one grounded rca from source unit to say tower amp. See if whining goes away. 
 

That’s the difficulty of this problem, is that it’s hard to pinpoint. It COULD be your source unit, but nobody knows. 
 

Where do your amplifier grounds go to? Where does your engine ground go to? Perhaps move all amp grounds straight to stereo/house battery. 

[samahickman]

Oh awesome! I had never heard of grounded RCAs. Should I just ground the RCA to the negative battery terminal?

Black box is powered and grounded off JL amp. All 3 amps are powered and grounded through a Rockford distributor block, which is grounded on negative battery terminal and powered direct from the isolator switch. 
 

thanks for all the ideas and help, Brandon!

[Brandonloos21]

I have heard of people using special RCAs and what they do is take the external shield of the rca (ground) and connect it to the same ground of the headunit. 

[samahickman]

3 hours ago, Brandonloos21 said:

I have heard of people using special RCAs and what they do is take the external shield of the rca (ground) and connect it to the same ground of the headunit. 

10-4

[MLA]

9 hours ago, samahickman said:

Update: I ended up calling a local marine stereo install shop in Minneapolis (where I’m located). Their take was that I just have my gain settings to high. They primarily do JL installs and said that 99% of them have gain settings at the 9 o’clock position (whereas mine were at the 3’oclock position). Will give it a go!

Gain level has zero, I mean NOTHING to do with the brand. If they set all their favorite brand of amps at the same level they are ignorant. A gain setting is a relationship between the media unit, the amp and driver the amp is powering. Change one specific component, and the gain is different. 

Gain hiss and "engine" noise are quite different. 

A failing alternator can induce unwanted noise when the engine is on v's off.  

[justgary]

On 6/21/2023 at 11:53 AM, samahickman said:

I’m thinking my problem is not typical engine whine, since it doesn’t change with RPMs

Does it happen for a few seconds with key on, engine off?  I'm thinking the fuel pump is one of the few things not related to RPM.

What year and engine do you have?

[samahickman]

8 hours ago, justgary said:

Does it happen for a few seconds with key on, engine off?  I'm thinking the fuel pump is one of the few things not related to RPM.

What year and engine do you have?

Interesting, Gary! I honestly don’t how how to test that because it’s a push button, no key. 
 

2014 350 Monsoon

one update: I have Rockford amps and they have a feature called “punch eq”, which dials up bass and treble. When I turned that off on the amps, the static/ring probably dropped in half. So, between that and just reducing my gains, I’ve made a lot of progress! Still there but u need to be listening real close!

[samahickman]

UPDATE: I brought up the ringing to MN Inboard when I dropped boat off for winterization. They said the issue was almost certainly the tower speaker adjustment knob in glove box. They claim that they get complaints about ringing/interference coming through speakers and the fix is to disconnect the tower speaker volume knob and route RCAs direct into black box. They called today and said they did just that and it's now fixed. I won't know for sure until Spring, but they claim it's gone. Posting now in case anyone can benefit from this info earlier than next spring!!

[MLA]

3 hours ago, samahickman said:

They said the issue was almost certainly the tower speaker adjustment knob in glove box.

Never seen one installed OEM on a Bu. 

[samahickman]

1 hour ago, MLA said:

Never seen one installed OEM on a Bu. 

I THINK they said that the tower control knobs were included w/tower pkgs from 2009-2014, but I don’t remember that for sure. It definitely looks OEM. Wish I would’ve taken a picture for you, MLA!