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high ground resistance when deck is on?

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bullman96 
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Posted: November 21, 2004 at 3:03 PM / IP Logged  
last night i noticed that i had a bit of distortion in the highs with the volume at a generous level. my grounds resistance with the deck off is about .3ohms while with the key in the acc position, it is about 20-30 ohms. could the ground be the problem or should i look elsewhere?
winston_smith 
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Joined: November 17, 2004
Posted: November 21, 2004 at 7:27 PM / IP Logged  
i'm no expert but,
Maybe your amp is being driven into distortion, or it could be your hu distorting if your running them off the hu. Also might be the amp is getting a clipped signal from the hu.
DYohn 
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Joined: April 22, 2003
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Posted: November 21, 2004 at 10:55 PM / IP Logged  

bullman96 wrote:
last night i noticed that i had a bit of distortion in the highs with the volume at a generous level. my grounds resistance with the deck off is about .3ohms while with the key in the acc position, it is about 20-30 ohms. could the ground be the problem or should i look elsewhere?

What ground are you measuring?

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bullman96 
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Posted: November 21, 2004 at 11:39 PM / IP Logged  
the amps gound. i disconnected the grounding wire connected to the chassis from the distribution block. all the amps were disconnected, but i had the car on because it was cold and i wanted some heat. the deck was on as well.    and i had a resistance between 20-30ohms. i tried turning the car off and the problem still was there, deck was still on. turned off deck, the resistance went back down to .3 ohms.
car on, deck off and it was still fine. any ideas dyohn?
DYohn 
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Posted: November 22, 2004 at 10:40 AM / IP Logged  

bullman96 wrote:
the amps gound. i disconnected the grounding wire connected to the chassis from the distribution block. all the amps were disconnected, but i had the car on because it was cold and i wanted some heat. the deck was on as well.    and i had a resistance between 20-30ohms. i tried turning the car off and the problem still was there, deck was still on. turned off deck, the resistance went back down to .3 ohms.
car on, deck off and it was still fine. any ideas dyohn?

If you took your reading between the amp and ground with the main ground from your distru block disconeccted, the 20-30 ohms you are reading is the difference between the amplifier ground plane and the chassis.  The amplifiers are now floating above the chassis ground.  I bet if you read voltage you'll get a few volts difference too.  The 20-30 ohms is normal and is what causes ground loop hum in a poorly grounded system.  That's whay you need to connect the ground to the same ground plane as the battery and alternator, to eaualize this difference and force the amps to operate at the same ground potential as the alternator.  If you have a 20-30 ohms reading WITH THE GROUND CONNECTED, which is what I feared you were measuring, then you simply have a poor amplifier ground connection and you need to improve it.

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bullman96 
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Posted: November 22, 2004 at 1:17 PM / IP Logged  
i was checking from the end of the ground wire to the battery. i also tried every other possible spot i could think of to gound and was still getting the same high resistance when the deck was on. i dont think it has anything to do with the grounding point.
DYohn 
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Posted: November 22, 2004 at 1:34 PM / IP Logged  

Was your ground wire disconnected?  If so, then what I was trying to say is it is not a problem.  If the ground wire is connected to the chassis and you get 20 ohms, then I believe you have a bad ground.  It may have everything to do with the grounding point, or your amp may have developed a bad internal ground plane.  The reason it only shows up when the amp is on is because that's the only time the internal output transistors are powered.

If I'm still missing your point, then I guess I would need to see it.  I suggect you go get your system looked at by a pro in your area.

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