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Alternator Whine...sort of
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<blockquote data-quote="spoonraker" data-source="post: 3321042" data-attributes="member: 570956"><p>I posted this before, but I got no replies so I'll try again.</p><p></p><p>First of all let me detail what exactly is going on. I am running a CarPC. All the sound is from the PC, there is no regular head unit anywhere. The PC is located in the trunk. The sound card from the computer outputs to a cable which converts the 3.5mm headphone jack to RCA, and that splits and plugs into my amps. None of the RCA cables are more than a couple feet long. Both of my amplifiers share a common ground point, which is directly bolted to the bare sanded down metal in the middle of the floor under the back seat. From the time I turn the key, it takes about a minute and a half for the computer to fully boot up (this will be reduced to about 25 seconds once I reinstall windows and do lots of tweaks) and during this time there is HORRIBLE alternator whine. The minute the sound card on the PC turns on 100% of the noise is gone.</p><p></p><p>I know most noise, especially alternator whine is caused by bad grounds. However in my case I don't have noise when everything is on, only when the amps are on but not receiving an input signal.</p><p></p><p>Do you think the noise is something I can stop by rewiring? If so where should I check, what kinds of test can I try to track down what is wrong. I do have a ground loop isolator and a DMM.</p><p></p><p>Do you think the noise is unavoidable? It's basically like turning your amps on, plugging an RCA wire in, and then plugging it into nothing. So any radiated noise near the signal cable would be transmitted directly to the amps.</p><p></p><p>Obviously if I delay the amp turn on until the sound card is turned on that will solve the problem, but how can I do that? The PC and the amps are on the same remote wire so simply putting a switch in the remote wire won't work. I'm not familiar enough with relays to make a delay for the PC, but if you have a diagram for one, post it up. Other ideas?</p></blockquote><p></p>
[QUOTE="spoonraker, post: 3321042, member: 570956"] I posted this before, but I got no replies so I'll try again. First of all let me detail what exactly is going on. I am running a CarPC. All the sound is from the PC, there is no regular head unit anywhere. The PC is located in the trunk. The sound card from the computer outputs to a cable which converts the 3.5mm headphone jack to RCA, and that splits and plugs into my amps. None of the RCA cables are more than a couple feet long. Both of my amplifiers share a common ground point, which is directly bolted to the bare sanded down metal in the middle of the floor under the back seat. From the time I turn the key, it takes about a minute and a half for the computer to fully boot up (this will be reduced to about 25 seconds once I reinstall windows and do lots of tweaks) and during this time there is HORRIBLE alternator whine. The minute the sound card on the PC turns on 100% of the noise is gone. I know most noise, especially alternator whine is caused by bad grounds. However in my case I don't have noise when everything is on, only when the amps are on but not receiving an input signal. Do you think the noise is something I can stop by rewiring? If so where should I check, what kinds of test can I try to track down what is wrong. I do have a ground loop isolator and a DMM. Do you think the noise is unavoidable? It's basically like turning your amps on, plugging an RCA wire in, and then plugging it into nothing. So any radiated noise near the signal cable would be transmitted directly to the amps. Obviously if I delay the amp turn on until the sound card is turned on that will solve the problem, but how can I do that? The PC and the amps are on the same remote wire so simply putting a switch in the remote wire won't work. I'm not familiar enough with relays to make a delay for the PC, but if you have a diagram for one, post it up. Other ideas? [/QUOTE]
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