Question about Phase Linear UPA424CS Car Audio Amplifier

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Whining noise from amp.

Is it possible that the noise is coming from the positive line from the bat. When I turn the car key to the first positon I hear the radio and it is claer as a bell. Then I turn the key to the second position and the noise starts. Then I start the car and it gets alittle worse. Its coming from the alternator i cna hear that. I have tried 2 spots for grounding. I have changed my grounds my wires and everything else. My RCA plugs are running from the radio straight down the dash under the rug to the amp. There are some vents but really no wires. The amp is a Phase linear upa424. The car is a mountaneer. The speakers I have running from the harness to the amp. Could that be the problem? I have been tring to fix this for a week now on and off. I am not much to ask for help but here I am. Is it possible the noise is coming from the positive from the battery? I have it connected directly to the terminal.

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  • danieldalbey Feb 13, 2009

    I am going to try the open rca first then the ground. I have had the head unit connected with out the amp and I had no noise what so ever. I am thinking that maybe there was some noise that I just couldnt hear. Putting the amp on has made the noise lound enought to hear. This site is awesome. Thanks. I will let you know what i find out.

  • danieldalbey Feb 13, 2009

    OK I tried the rca cables. I had readings of 0.3 to 0.4 between the head unt and the rca cables. I tried the ground to the battery and no change. Next will be the noise filter. I am going to run that and get back to you.

  • thunderboy8 May 11, 2010

    try running a ground to the battery. if no good, then try put a 'noise filter' on the power supply to the amp/head unit.

  • Perry Babin May 11, 2010

    You may have open shields on the RCA output of the head unit. The procedure to check them can be found on the following page.

    Testing RCA Shield Ground

    Let me know if you have any other questions.


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Hear are couple things to try   try running your power and  (ground) both directly from your battery   to the amp and  to the receiver .. if this doesn't help try purchasing a noise suppressor  and wire your receiver threw this  it should solve your problem  

Posted on Feb 17, 2009

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