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Old 05-19-2013, 09:45 PM
mcookgraphics mcookgraphics is offline
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Dual battery stereo noise

Used the ultimate dual battery thread to set up 2 batteries in my 01 x-star. Works great, other than at low speeds I hear engine noise through the speakers with stereo. Any ideas how to fix?
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Old 05-19-2013, 10:43 PM
MLA MLA is offline
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Where is the head-unit's yellow B+ drawing from? having the head-unit and amps drawing from different batteries in a dual-battery boat is a common cause of unwanted noise. They need to draw from the same battery source.
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Old 05-19-2013, 11:25 PM
mcookgraphics mcookgraphics is offline
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Head unit is still on first battery. Thanks for the info. I'll try and locate/move wire and see if that helps.
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Old 05-20-2013, 12:29 AM
chevyluv chevyluv is offline
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ive got the same boat and exact same problem il have to try this to
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Old 05-20-2013, 07:24 AM
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bturner2 bturner2 is offline
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Most noise problems can be traced back to grounding. Correct wire sizing and termination are typical places to start.
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Old 05-20-2013, 09:26 AM
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mcook,
A ground loop or supply loop can equally induce noise because this encourages the flow of DC current between components in the signal path. The engine noise is always present but normally you do not give it an inroad to audio.
All grounds are common. However, it may be important that the source ground is heavier, shorter and direct to the ground point closest to that of the amplifier(s).
The same thing would apply to the B+ side. This would include both the ign/acc and the memory. Sometimes you have to remove these supplies from the factory harness and go direct to the same point as the amplifier(s) supply.
But the biggest issue is that all audio electronics are wired to the output post of the dual battery switch and do not go battery direct. This totally eliminates any possibility that the amplifier could access one battery and the source unit could access the other battery (which will often have varying voltages). With any voltage differential, current will flow through the path of least resistance, and you do not want that path to be the audio path.

David
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Old 05-20-2013, 09:35 AM
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Traxx822 Traxx822 is online now
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I'm battling the same issue. So you are saying the head unit needs a different power source more directly related to a direct power source same as the engines? That would be why the noice is less if the switch is set on dual while the engine is running.

Would an added battery and direct wiring do the trick? In lamens terms, what is the best route to wire this up so I can get rid of my noise too?
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Old 05-20-2013, 10:36 AM
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Quote:
Originally Posted by Traxx822 View Post
I'm battling the same issue. So you are saying the head unit needs a different power source more directly related to a direct power source same as the engines? That would be why the noice is less if the switch is set on dual while the engine is running.

Would an added battery and direct wiring do the trick? In lamens terms, what is the best route to wire this up so I can get rid of my noise too?
Follow these simple instructions.
When using a dual battery switch, the engine alternator/starter feed, helm buss, and all stereo equipment should go to the dual battery switch output post. Nothing but a bilge pump/float switch (if applicable) would go battery direct.
ALL audio equipment should share the same ground point. Closest to the amplifier(s) primary terminals is best.
ALL audio equipment should share the same B+ point. Closest to the amplifier(s) primary terminals is best.
Quality of cables and especially quality of connections/terminations is important.
Amplifier input gains should be set correctly which means they should not be maxed out.
This will eliminate 99% of noise problems.

David
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Old 05-20-2013, 11:03 AM
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Thanks Ear,

I have a couple more questions.

In an earlier post you stated " But the biggest issue is that all audio electronics are wired to the output post of the dual battery switch and do not go battery direct. This totally eliminates any possibility that the amplifier could access one battery and the source unit could access the other battery (which will often have varying voltages)."

Then you stated " When using a dual battery switch, the engine alternator/starter feed, helm buss, and all stereo equipment should go to the dual battery switch output post. Nothing but a bilge pump/float switch (if applicable) would go battery direct."

So I am confused on this point.

If all audio equip has to go to the switch post, How am I supposed to get it all to the same B+ point. Wouldn't the switch determine what battery I am getting the power from?

Here is another thing which may spark an answer. When I switch the dual switch to "ALL" instead of 1 or 2, the noise is half what it is if only set to one of the other. The other issue is that when I turn up the volume, about half way up, the noise seems to go away. Maybe because its being drowned out but it goes away.

Last you mentioned the same ground spot. Which I do not comply there. Currently I have both batteries grounded to the transmission. I am going to run a ground cable from one to the other and then to the switch to see if that fixes it.
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Old 05-20-2013, 12:56 PM
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Both batteries should be grounded to the engine block since that is the largest metal mass on the boat. Perhaps the transmission is the same or perhaps not. I'm not in a position to form an absolute conclusion.
B+ means the 'positive' voltage or just plain 'positive/+'.
The first two statements you quoted are saying the exact same thing. In case you are confused, the first statement is about the intended objective and about not about describing the problem.
All grounds are common. All positives will be common per the above instructions. However, there can be resistance inequities based on distance and gauge. And, resistance equates to a voltage differential. Not knowing where your batteries are located in respect to the audio equipment and namely the amplifiers, the safe route is to get the source electronics + & - from as close to the amplifier primary + & - terminals as possible. Of course the amplifiers will get their + from the dual battery switch and their - from the battery.
So you can ignore just about everything and just follow the simple instructions listed above in my prior post.

David
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