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

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Re: humming noise thru my speakers

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

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Hello, if you know how to use a volt/ohm meter and you are comfortable with taking the bottom cover off the amp I can assist you in testing a few things to narrow down the problem. The easiest way would be to talk to you on the phone if you don't mind. I own a car audio installation and amp repair shop. If you want to do it by e-mail we can do that to. I would have to walk you thru the steps, it would'nt take long. Taking the amp out and taking the cover off takes longer. Anyway let me know. It sounds like you may have a power supply problem. Or, it could be a few other components inside. It's hard to say without doing the test that I would help you with first. Cause the amp is coming on but you say with some thumps coming from sub and nothing from the other speakers. It maybe doing the same on the other speakers but because there are crossovers on them it would cut off that low frequecy noise. You could also maybe have some shorted output transistors but like I said, have to do thaqt initial test first if your up to it. Send me a private message so I can get your info or i'll give you mine to decide what you want to do.

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If the subs are making a humming or RPM sound check your ground on the amp , make sure its a good ground. Always run your power wire from battery by itself down one side of vehicle. Groun should be no longer than 2 feet. If that dont help you can buy a noise supresor that goes inbetween your head unit and amp through RCA's with a ground on it . Hope this helps.

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Hi Justin,
Send me the specs. on the speaker ( voice coil impedance), amp, power wire size, and box
As for engine noise ( alternator whine) 99.9 times out of a hundred it's caused by what's called a ground loop, That will take a little trouble shooting on your part. It's no big deal. It will be a step by step process. All you need is two alligator clips or a old RCA cable.and a couple feet of wire. I'll try to get to it this evening,
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If you know how to use a multimeter, you can test the amp this way:

-unhook the subs
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-unhook the audio inputs
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-put the positive probe on the inside of the input connector, being sure you make contact with th inner contact
-take the negative probe and tap it on the outside of the connector

What you are doing is sending a low voltage (replicating an audio signal) into the amp audio circuit and allowing the amp to amplify it. If the amp makes the speaker pop each time you strike the probe, the amp is working.

There is an inherent problem with band passes. The naturally filter out high frequencies like a crossover, including distortion, so it makes it hard to hear when the subs begin to protest.

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may be the ground of the rca or in your stereo. and many times in the inlet of the amp. good look.

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