Rear Speaker Balance - AVS Forum
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post #1 of 6 Old 02-23-2011, 07:44 PM - Thread Starter
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Hey all,

I recently installed a 5-channel Alpine amplifier in my Chevy Avalanche (2002 - Z71) and am having an issue with the rear balance. I used the PAC GM21c unit to convert the signal to RCA outs to the amp. For some crazy reason, both of the rear channels (L&R) continue to play when the balance is adjusted to the left or right. All that happens is the music gets slightly softer in both channels. I am certain that it is hooked up correctly. The balance works perfectly for the front speakers. I've ruled out the amp being the culprit by checking for signal in the L&R RCA cables when balanced all the way to the left or right. Both carry a signal. I have contacted PAC and the customer service representative said that it is the fault of the OEM head unit and not their product. He had no help for me . I don't think I was having any rear balance issues before the installation of this product. Has anyone here experience anything similar with this product? Suggestions? Thanks in advance for any replies.
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post #2 of 6 Old 02-23-2011, 10:30 PM
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Your HU outputs are most likely floating ground (the speaker grounds are a different kind of ground from say.... the frame of your car)

Does your amp not have high level inputs? Most of them do, so if you have then just delete the pac and hook directly to the amp.
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post #3 of 6 Old 02-24-2011, 01:09 PM - Thread Starter
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No line level inputs. RCA only.
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post #4 of 6 Old 02-24-2011, 10:40 PM
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I know it may not be easy, but can you swap the inputs from the front to the rear on the Pac? Heck, I would check each channel with your balance and fade controls. First verify that it is not in fact your Pac unit. Even if you have to hook the front outputs of the factory amp to the front inputs of the Pac and then the rear inputs of the Pac. Then if the Pac works as it's supposed to, then start trying to see if the factory amp is not providing a seperate stereo rear output. the rears could be a summed mono signal out of the factory amp. this would cause the "softening" you spoke of.

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post #5 of 6 Old 02-24-2011, 11:54 PM
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Quote:
Originally Posted by chaddlyd View Post

No line level inputs. RCA only.

Then you will need a floating ground adapter in between the PAC and the HU. Something like this:

http://david-levy-company-inc.amazon...ffId=the005-20

My guess is that the PAC has not got the ability to deal with floating ground, which is extremely common in stock radios (it's cheaper to do).

Floating ground simply means that the ground wire from each speaker is not ACTUALLY at 0 volts (absolute ground like the frame of your car) so you can't treat them like common grounds and connect them together. You will get leakage and cross flow between channels if you do. Meanwhile the PAC is most likely treating the speaker negative lines as common ground, (absolute 0 volts) and connecting them together.
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post #6 of 6 Old 02-28-2011, 08:53 PM - Thread Starter
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Thanks for your replies. The issue I see with the common ground converter is that the PAC plugs directly into the factory HU, so there is no "in-between the HU and PAC". I have not had time to pull the unit and switch the RCAs, but I have switched them on the amp with the same results. I'm going to look into hooking the PAC to the harness that goes into the factory amp, but I'm not sure if it is the same connection.
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