Question about Phase Linear UPA424CS Car Audio Amplifier

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Humming noise thru my speakers

I bought the amp and installed it a couple of weeks ago and since then i always get this humming noise and when i step on the gas to my jeep is gets louder and louder

Posted by big tony on


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You are getting engine noise through your amplifier. To solve this problem you will need to install a filter in-line with the DC path, or install a voltage regulator in-line with the DC path.

Posted on Sep 08, 2007

  • Anonymous Sep 12, 2007

    Hello Big tony ,

    I usually don't reply to the double red squares, but in this case I am kind of perplexed, short of me telling you how to change out your alternator to a new one with clean brushes (the cause of the voltage spikes) and getting a new voltage regulator. That's about all that can fix this problem. However that solution does not make any sense. You have voltage spikes on the line and the only way to remove them is with an LC (inductor/capacitor) filter in-line with the DC path. Your problem is that the amplifier is amplifing these voltage spikes or your amplifier is not properly filtering out the incoming spikes. But the fact is your dc voltage has spikes on it and a way of removing those spikes is with a LC filter. Or on the off chance that it is the power supply in the amplifier, take of the cover off and find the main voltage input and use an oscilloscope to see if the DC voltage is clean (free of voltage variation) This may mean that you have to replace a filter capacitor in the amplifier. Other then this your options are all spent.

    I am sorry I did not give you the answer you were looking for but, I have always felt that being honest makes one a good technician, and non-complicated problems deserve non-complicated answers.

    Thank you and I hope that you find what you are looking for.



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