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-   -   Stereo System high pitch hum (http://www.mastercraft.com/teamtalk/showthread.php?t=57893)

djue 10-19-2013 09:32 AM

Stereo System high pitch hum
 
I have a 2012 X30 with CMD6 clarion source unit and 3 JL amps. The system has always had a small high pitch hum that does not vary with RPMs. When I added a Wetsounds 420 SQ, the hum amplified. After hours of trouble shooting (grounds to one point, all B+ from the house battery pole on the battery selector, Rca wire isolation) I finally found that when I disconnect the clarion remote 8 pin DIN wire from the BIG computer, all noise disappears. Any ideas on how to get rid of this type of interference? Now, I just use my Wetsounds for volume control and have the unit disconnected from the BIG system.

Thanks
Donnie Jue

David Analog 10-19-2013 08:11 PM

You have taken the correct path thus far in your trouble shooting.
All the audio electronics should be wired to the 'Common' battery post (and not the battery bank post if that post is battery direct) if it is a conventional dual battery switch. If the computer is accessing power from a different battery bank then you have introduced a supply loop that is typically noise inducing. If the computer induces noise then the computer needs to access the the identical B+ point and the identical ground point as 100% of the audio gear including the source gear (HU & EQ). You can canabalize and standard RCA ground loop isolator for one of the small EI transformers contained inside. The transformer can be used to break the DC connection on either the DIN cable shield ground, another internal DIN cable ground wire or both.

djue 10-19-2013 08:26 PM

Thanks for the info! I'll confirm but I believe all B+ originate from the blue seas dual battery switch common. I also use Bosch style relays for ignition and remote circuits.
My stereo grounds go straight to one of the batteries. The Mastercraft BIG computer is grounded to a grounding bar near the engine. Could be a problem?
Do you now which pin on the clarion DIN remote is ground?

Thanks Again
Donnie Jue

David Analog 10-19-2013 08:44 PM

When it comes to Blue Sea, make sure you are making a distinction between a conventional dual battery switch and dual circuit battery switch. There's a big difference in application and Blue Sea makes both.
Tough to beat a ground close to the engine block grounded at the engine block (the largest metal mass on the boat). But if there is any resistance between this point and the battery ground point then you have a voltage differential and therefore a potential noise conflict.
I don't know what the ground pin is but the outer shield is a breeze to identify once you snap the DIN plug end apart. Clarion technical should be able to give you a pin diagram. The ground pin is easy enough to identify with a basic multimeter.

JimN 10-19-2013 09:01 PM

I would look at where the cabling is routed for the stereo. If it's bundled with other boat wires, it's possible that proximity is causing the problem. If it's possible to remove the remote's cable from where it's running and change the location, it's possible that moving it is the only thing needed to cure the noise problem.

JimN 10-19-2013 09:03 PM

Quote:

Originally Posted by David Analog (Post 986462)
You have taken the correct path thus far in your trouble shooting.
All the audio electronics should be wired to the 'Common' battery post (and not the battery bank post if that post is battery direct) if it is a conventional dual battery switch. If the computer is accessing power from a different battery bank then you have introduced a supply loop that is typically noise inducing. If the computer induces noise then the computer needs to access the the identical B+ point and the identical ground point as 100% of the audio gear including the source gear (HU & EQ). You can canabalize and standard RCA ground loop isolator for one of the small EI transformers contained inside. The transformer can be used to break the DC connection on either the DIN cable shield ground, another internal DIN cable ground wire or both.

So, you want him to make the shield useless by inserting an isolation transformer in-line?

djue 10-19-2013 09:42 PM

Great ideas!! I have an extra clarion remote cable. I'll run it temporarily away from all wiring and see what happens. I'll confirm my blue seas B+ common. If no luck, I'll run my stereo ground to the ground location near the engine with the BIG computer. Last resort, I'll try the remote wire ground loop isolator - if I can figure out how.

Donnie Jue

David Analog 10-20-2013 11:32 AM

Quote:

Originally Posted by JimN (Post 986472)
So, you want him to make the shield useless by inserting an isolation transformer in-line?

Can't answer a poorly constructed question.
But use the transformer? Absolutely, as a test at minimum.
The shielding function will still be intact just as it is with a standard RCA ground loop isolator. It simply keeps DC (that may be modulated, ie; noise) from passing down the shield from one device to another.

JimN 10-20-2013 12:46 PM

Quote:

Originally Posted by David Analog (Post 986525)
Can't answer a poorly constructed question.
But use the transformer? Absolutely, as a test at minimum.
The shielding function will still be intact just as it is with a standard RCA ground loop isolator. It simply keeps DC (that may be modulated, ie; noise) from passing down the shield from one device to another.

Beside cost, if this is a better way to shield, why don't the manufacturers break the shield and use a small value cap, in series? It would still act as an AC/RF shield, but there would be no DC connection (unless they're using the shield as THE ground).

I don't remember the last time I heard of a shield that was acting to cause this kind of problem when the cabling was routed correctly (away from major noise sources).

bhanson 10-20-2013 05:47 PM

Generically, sounds like a ground problem, but that is consistent with the more detailed answers above. Two data points, may or may not help, but more info:
1) Added aux-in on my Harley, got that buzzing, and ground loop isolator was quick/easy fix
2) I have an external Belkin bluetooth adapter on my X30 that plugs into the Alpine's aux-in, and sometimes that mini-jack gets jarred around in transport or on the water creating high-pitch whine. Unplug, plug back in, all is well.


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