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  #21  
Old 05-20-2013, 10:52 PM
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Originally Posted by ZachDaddy View Post
I know that your going to want to keep the RCA's away from the power wires. Do you know if your RCA's are shielded? Sounds like your problem is that the power and RCA's. That's your step one to see if the noise goes away.

David can give you the why for.
RCA cables are almost always shielded, to some extent. The issue is whether the shield is braided, foil, braided + foil, parallel stranded, parallel stranded + foil or twisted pair in some form with or without shield. Unfortunately, unplugging the RCA cables will eliminate the ground loop OR the noise when it's coming from induction. The only way to tell if the noise is coming from induction is to connect the RCA cables to a separate amplifier and listen for it. Radio Shack sells a little battery-powered amplified speaker that's great for this kind of troubleshooting and it's only about $15. An RCA-3.5mm adapter will be needed for this. If there's no noise, it's a ground loop. If the noise is from induction, increasing the distance between the power and audio cables is the only way to remove it.
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  #22  
Old 05-20-2013, 10:55 PM
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Originally Posted by EarmarkMarine View Post
Like Mike said above, it is possible to have noise radiated into the RCA cables by being in close proximity to power cables but it is extremely rare. In fact, I can only remember having to relocate RCAs as an actual or partial solution perhaps two or three times in nearly 15 years of having a dedicated marine audio division.

David
Ever work on a Malibu boat from '99-2001? They had a lot of problems with this. When I called to ask who installs the stereos, the service manager said "We have a guy who's good with this stuff", to which I replied, "No, he's not" and I explained why.
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  #23  
Old 05-20-2013, 11:01 PM
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Originally Posted by Traxx822 View Post
OK, I may have nailed it then. My Head unit is grounded to a different source than the amps. So I need to run power all the way back to the switch as well as ground all the way to the transmission?

I think i'm starting to get it. Sorry i'm so confused.
If you have more than one amp and are using distribution blocks for the B+ and grounds, you can run your head unit's new power wires to the blocks and connect there. If you do this, I would recommend using a Bosch-style relay to switch the Red wire, rather than using the red wire at the dash. You can, however, use that wire to trip the relay. This allows the head unit to turn off with the key or accessory switch, yet remain isolated from the wiring that's not going directly to the same place where the amp(s) take their power/ground. You would want to fuse the new B+ to the head unit at the distribution block- the ground doesn't need a fuse. These wires can be passed under the floor, going across from the driver's side to the passenger side and they should be in wire loom, for protection.
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  #24  
Old 05-21-2013, 10:08 AM
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Quote:
Originally Posted by ZachDaddy View Post
I know that your going to want to keep the RCA's away from the power wires. Do you know if your RCA's are shielded? Sounds like your problem is that the power and RCA's. That's your step one to see if the noise goes away.

David can give you the why for.
The AC ripple created by the alternator that runs through the power cables normally isn't of enough gain to travel through air and be collected by the center and shielded conductor of a decent RCA cable. It normally requires an added element of inductance whether a very long coincidental/tight run or a coil of sorts. And even this is exteremely rare based on the number of vehicles that run 20 foot RCAs to the trunk along side the power cables and do not have a trace of noise. Generally this is a misdiagnosis.
The test that Jim outlined with a Radio Shack battery-powered amplifier (I own and use one) is effective in sniffing out the source of noise. But with an open-ended RCA you have created an antenna that is very different from the usage where both ends of the RCA cable are terminated. So be sure to make this important distinction.

David
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  #25  
Old 05-21-2013, 10:37 AM
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Quote:
Originally Posted by JimN View Post
If you have more than one amp and are using distribution blocks for the B+ and grounds, you can run your head unit's new power wires to the blocks and connect there. If you do this, I would recommend using a Bosch-style relay to switch the Red wire, rather than using the red wire at the dash. You can, however, use that wire to trip the relay. This allows the head unit to turn off with the key or accessory switch, yet remain isolated from the wiring that's not going directly to the same place where the amp(s) take their power/ground. You would want to fuse the new B+ to the head unit at the distribution block- the ground doesn't need a fuse. These wires can be passed under the floor, going across from the driver's side to the passenger side and they should be in wire loom, for protection.
I have highlighted my confusion above.


What is the benefit to that relay? I like being able to turn the key off and the radio/amps stays on. The only time my amps or head unit shut off is when I flip the dual battery switch to off or manually turn them off. I understand the point of it and how it works but how would I run it through a switch on the dash and run both power and ground to the same source the amps gets it from? I have an extra unused switch.

I have all my RCA's running through the bow. All in wire loom. I have Stinger SI8420 & 8220's so they are decent RCA's. Do I need to run the new power and ground in separate loom from the RCA's? (remote is obviously already run along in the same loom as the RCA's)
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  #26  
Old 05-21-2013, 10:50 AM
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Traxx,
We have already established that you want to get the HU supply at the same point as the amplifier supply in order to get rid of any potential voltage differential and get rid of noise.
However, that would serve to circumvent the key function. If you do not want the key function then ignore the relay option. For those who want to maintain the key function the interrupt relay allows for both objectives.

David
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  #27  
Old 05-21-2013, 10:50 AM
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Originally Posted by EarmarkMarine View Post
The AC ripple created by the alternator that runs through the power cables normally isn't of enough gain to travel through air and be collected by the center and shielded conductor of a decent RCA cable. It normally requires an added element of inductance whether a very long coincidental/tight run or a coil of sorts. And even this is exteremely rare based on the number of vehicles that run 20 foot RCAs to the trunk along side the power cables and do not have a trace of noise. Generally this is a misdiagnosis.
The test that Jim outlined with a Radio Shack battery-powered amplifier (I own and use one) is effective in sniffing out the source of noise. But with an open-ended RCA you have created an antenna that is very different from the usage where both ends of the RCA cable are terminated. So be sure to make this important distinction.

David
I should have been more specific- the RCA cable should be unplugged from the amp and plugged into the amplified speaker. Then, it must be determined whether the noise is coming through the head unit (via bad filtering) or coming from the cabling originating at the head unit, i.e., an induced noise.
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  #28  
Old 05-21-2013, 10:55 AM
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You can also leave the RCA cable plugged into the existing amplifier, unplug the RCA from the HU, and short the left to right RCA at the HU end with a female to female barrel.

David
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  #29  
Old 05-21-2013, 11:04 AM
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Quote:
Originally Posted by EarmarkMarine View Post
Traxx,
We have already established that you want to get the HU supply at the same point as the amplifier supply in order to get rid of any potential voltage differential and get rid of noise.
However, that would serve to circumvent the key function. If you do not want the key function then ignore the relay option. For those who want to maintain the key function the interrupt relay allows for both objectives.

David
Thats what I thought. Thanks.
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  #30  
Old 05-21-2013, 11:05 AM
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Originally Posted by Traxx822 View Post
I have highlighted my confusion above.


What is the benefit to that relay? I like being able to turn the key off and the radio/amps stays on. The only time my amps or head unit shut off is when I flip the dual battery switch to off or manually turn them off. I understand the point of it and how it works but how would I run it through a switch on the dash and run both power and ground to the same source the amps gets it from? I have an extra unused switch.

I have all my RCA's running through the bow. All in wire loom. I have Stinger SI8420 & 8220's so they are decent RCA's. Do I need to run the new power and ground in separate loom from the RCA's? (remote is obviously already run along in the same loom as the RCA's)
The red wire in the dash, when connected to a head unit that uses a different source for the yellow wire, will cause noise, in most cases. The relay would completely isolate the red wire from the head unit because it's only being used to trip the relay. You can use whatever you normally use the red wire for, but the B+ should come from the same source as what powers the amplifiers. If you use a power wire from one battery and the others connect to the other battery, you lose voltage and this has to be made up somewhere, so it tries to balance itself by traveling on the audio cables.

Your routing of the audio cables through the bow makes them susceptible to picking up noise- they should be as short as possible and if you have an electrician's fish tape, you can usually find a shorter path. However, you need to find out if they'll be running parallel to other current-carrying wires.

It's possible to run audio cables parallel to power cables, but it's not recommended, in 12V (cars/trucks/boats, etc) or in homes/offices. Any intersections should be as close to a right angle as possible because it picks up the noise more easily when the paths are parallel. This all has to do with magnetism- With square or rectangular-shaped magnets, each side can have a specific pole direction and with wire, the field is basically parallel to the direction of the wire. If the wires are parallel, their respective fields can link together and if they intersect at a right angle, the space where their fields coincide is much smaller, so the effect will be decreased.
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