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Audio...or any other stereo gods

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Old 07-10-2002, 09:53 PM
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jr
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Default Audio...or any other stereo gods

Hey guys, I got a problem. I installed 2 new amps in my boat with the old Sony stereo that was in it. The old stereo with out the amps was fine when the motors were running.

After I put in the amps with noise filters I get noise so bad you cant even here the music. With out the motors running everything sounds great.

I had long runs on the cables to the amps. Now I'm relocating them to with in about 3 feet of the batteries. I'm pulling RCA cables the the amps from the cabin for the signal.

Will the RCA cable pick up the alternator noise from the wiring as it runs back to the amps? Or will it sheild the signal. Also with the remote on wires for the amps, are they a constant 12 volts from the radio when the stereo is on or a pulse of 12 to turn on and a pulse of 12 to turn off. Thanks guys.
 
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Old 07-10-2002, 10:07 PM
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The remote wires for the amps are constant 12V . As for the other problem buy the best shielded rca's that you can find. Cheap RCA cables can pickup interference from other electrical stuff.
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Old 07-10-2002, 11:13 PM
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Lightbulb Did you try...

...unplugging the RCAs? If the noise is in your power/remote wire, it will still be there. There are also jumper wires available to ground out the RCAs for testing.

Is it a whining or a clicking? The whining is usually alternator noise, while a clicking is ignition.

Alternator noise may be a ground loop, ignition noise may be a magnetic field from the coil.

I do not like installing noise filters on audio equipment, as they are usually a band-aid for a problem that can sometimes be solved without degrading the signal (I.E. grounding problems). Most stereo shops will just throw noise filters on cuz it's easier than rewiring.

Remote wires are a constant 12 volts on.
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Old 07-10-2002, 11:38 PM
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Havasu, I had a filter on the Remote Power also. I had one laying around and put it on just in case.

The noise I get will be either motor noise from the blower or bilge, or alternator if no electric motors are running.

I understand the need for a good ground. But how do you get one better than 1. a engine block ground 2. transom assembly ground or 3. direct to the battery? I've tried them all and none are better than the others.

My next step will be to move the stereo to the other side of the cabin. But guess what no ground. So if I bring one back to it from the engine compartment guess what. A 10 foot ground wire which I thought was a no no.

The stereo and amps are on different grounds. The stereo is on one from behind the instrument panel and the amps come back from the engine from a separte 4 GA. ground. But arent they still the same ground?

Another thought I had, but cant remember my electronics class. Can I wrap the long positive cable, with the ground cable and cancel out the noise, or have it act as a shield? Much the same as a co-ax cable? Just a thought.

I'm open to any suggestions. Thanks Guys.
 
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Old 07-11-2002, 12:02 AM
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Default Hmmm....

...if it were me, I would look here first:

Quote:
Originally posted by jr
The stereo and amps are on different grounds. The stereo is on one from behind the instrument panel and the amps come back from the engine from a separte 4 GA. ground. But arent they still the same ground?
A ground loop is usually caused by the RCAs acting as a ground, bridging the amp and the head unit. In boats, I have had the most success running long beefy positive & negative cable (2-4 gauge) to distribution blocks, then the smaller (8 gauge) wires to the audio equipment.

If all the audio equipment is on one cicuit, there is less chance for noise from the other sources (blower motors, etc.). You can even run a dedicated battery (or 2) with an isolator, to separate the audio stuff from electrical interference.
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Old 07-11-2002, 01:03 PM
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Up to this point I wasn't running rca's. My head unit only has 2 RCA outs. I was using the Speaker level outs to go to the hi level inputs on one 4 channel amp. The second 2 channel sub amp was going to get the rca's. But it wasn't wired in yet. The first thing I'm going to do is move the head to the other side of the boat so its away from the rest of the electronics. Then it and the amps get their own dedictated ground and power cables. I was already running distibution blocks.

Thanks for the info.
 
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Old 07-11-2002, 03:18 PM
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Cool Well partner...

...your well on your way. I will bet $1 that it gets better. If you are using those "high level inputs", your amp will be amplifying the noise from the head unit speaker "outs"...

Have you considered a "Y adapter" for the RCA's? Might sound better than the "high level" inputs...those things are noisy...

A quick experiment would be to run a jump wire from the dist blocks to the head unit power and ground to isolate it...

Good luck! Let me know how it turns out...

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Old 07-12-2002, 07:34 AM
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FIXED!!!

The problem was the different grounds for the head and the amps. Once I combined them all the problems went away. The next step is to experiment with the high level inputs and see if they are usable. I an using the Y cables now with experimenting with the line level inputs but my gain is maxed out because I'm spliting the voltage. I'm not getting the output I should. If I can use the high inputs and still get no noise then thats the way to go. Then the line level inputs will go to the 2 channel amp.

I'll let you know how it goes.

Hint everyone. Save yourself alot of grief. If you install a stereo make sure all the components are on the same ground. From the same source. Such as a large cable to a distribution block and smaller cables, from there.
 
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Old 07-12-2002, 09:02 AM
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That is ussually in a boat anyhow the only way you will get engine noise. If that is done correctly you can almost always point at a faulty piece of equipment. I saw the post late last night but noticed you already had the correct advice. Good job
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Old 07-12-2002, 10:12 AM
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Another tip/trick for anyone else doing their own install is to NOT run the RCA's along side the power/ground wires! That will give you noise as well. And if you doo need to cross over either one try and cross them at 90* angles.
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