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<blockquote data-quote="smoka" data-source="post: 6156333" data-attributes="member: 606721">The shielding of your RCA&#039;s connect ground from your amp to your deck. If any extra current runs through the RCA&#039;s then you can get engine noise out of your speakers.If you ground at two different spots, you have the same 12v going to the amps, but the grounds have a slightly different resistance (one spot may pass through more welds than another). This difference in resistance causes a slight potential energy difference between the two amps (i.e. if you connect a voltmeter between the 2 grounds spots you may see a small voltage). The RCA&#039;s on your cd player usually have the shielding connected together internally to ground. When this happens, the amp that sees the higher resistance might pass some ground current through the RCA&#039;s which interferes with the audio signal that is being sent. But when the amps are grounded in the same spot (or better yet connected straight to the neg batt terminal), there is not much chance for any potential energy to exist. Hope that makes sense, I could have probably explained it better.If you watch this forum enough, engine whine is one of the most common topics. Some times its unavoidable even if you do everything right. Often people with Pioneer (or other) cd players will add a ground connection straight to the rca shield.<a href="http:////forum/showthread.php?t=198477" target="_blank">http://www.caraudio.com/forum/showthread.php?t=198477</a></blockquote>

[QUOTE="smoka, post: 6156333, member: 606721"] The shielding of your RCA's connect ground from your amp to your deck. If any extra current runs through the RCA's then you can get engine noise out of your speakers. If you ground at two different spots, you have the same 12v going to the amps, but the grounds have a slightly different resistance (one spot may pass through more welds than another). This difference in resistance causes a slight potential energy difference between the two amps (i.e. if you connect a voltmeter between the 2 grounds spots you may see a small voltage). The RCA's on your cd player usually have the shielding connected together internally to ground. When this happens, the amp that sees the higher resistance might pass some ground current through the RCA's which interferes with the audio signal that is being sent. But when the amps are grounded in the same spot (or better yet connected straight to the neg batt terminal), there is not much chance for any potential energy to exist. Hope that makes sense, I could have probably explained it better. If you watch this forum enough, engine whine is one of the most common topics. Some times its unavoidable even if you do everything right. Often people with Pioneer (or other) cd players will add a ground connection straight to the rca shield. [URL="http:////forum/showthread.php?t=198477"]http://www.caraudio.com/forum/showthread.php?t=198477[/URL] [/QUOTE]

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