Question about US Acoustics USX-4065 Car Audio Amplifier

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US Acoustics USX-4065

My amp seems to cycle on and off when cold. It works great all summer long, but as soon as winter rolls in it is useless. It has done this since new. Just after I bought it I read that this amp had this problem, but now I can't seem to find anyone else with the same problem. I run the bass tube on channels 3 and 4 bridged and a pair of Jensen 6x9's on 1 and 2. It is beyond warranty now and US Acoustics would not admit to any design problems and said I could return it for repair. Any suggestions?

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Re: US Acoustics USX-4065

Yeah, mine does the same. i think its shot from nov-april, then it magically fires back up

Posted on Feb 20, 2008

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Re: US Acoustics USX-4065

My suggestion is to take it to a local repair shop and have them look at it

Posted on Dec 06, 2007

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1 Answer

Red light is on amp wont work worked before then all of a sudden the light came on?

There is a possibility that there is a cable which was coming in contact with metal wearing it out eventually and causing a short making the amplifier go into protect or you have a shorted/damaged speaker. Check your cables. With the info you provide, thats the best i can do hope this helps dreamsystems

Feb 08, 2011 | US Acoustics USX-4065 Car Audio Amplifier

1 Answer

How many watts

  • 120 watts x 4 at 2 ohms
  • 240 watts x 2 in bridged mode
  • Jan 12, 2011 | US Acoustics USX-4085 Car Audio Amplifier

    1 Answer

    So i have this usx 4085 that someone threw in with some twelves on a deal, now is it even worth it to hook them up together or just buy another amp?

    It depends on the quality of the 12s and voicecoil configuration.
    Do you know the lowest impedence the amplifier will operate? is it bridgeable?
    Howabout any low pass crossovers built in?
    I would wait for a better amplifier than risk damaging the 12s if they are worth anything.

    Thanks for using FixYa - a 4 THUMBS rating is appreciated for answering your FREE question.

    Nov 25, 2009 | US Acoustics USX-4085 Car Audio Amplifier

    1 Answer

    My amp plays but it smokes

    Please, Please, stop using it, the fact it plays is a malfunction in itself, so get it fixed or get a new one b4 you light your car on fire...

    Oct 07, 2009 | US Acoustics USX-2100 Car Audio Amplifier

    1 Answer

    No sound out of it, took it apart and found one of the Irfz44n mosfets burned up and the resistor right beside it burned too, What would cause this?Thanks

    Hello rjhunting,

    Most often the output MOSFET's and associated circuitry will burn out when the amp draws excessive current. And excessive current draw is most often caused by operating the amp into an impedance that is too low. Of course, depending on the age and actual use, the amp could have failed from normal use. The US Acoustics USX-4085 is a relatively good quality low-end amp that was manufactured with excellent components.

    All of their amps manufactured after 2001 carried a 3-year warranty. But when operated in "tri-mode", with normal speakers and a subwoofer, the subwoofer minimum impedance rating was 8 ohms. And the normal speakers should be operated through a high pass capacitor while the sub needed a 15.9 mH low pass filter inductor.

    The MOSFET's and resistors can probably be replaced at a qualified electronics shop. If you are somewhat handy with a soldering iron and have a controlled temperature soldering station, you can do it yourself. Parts are available from: and

    Hope this helps.

    Sep 27, 2009 | US Acoustics USX-4085 Car Audio Amplifier

    1 Answer

    Protection light flashes on and i get nothing

    Hello shwoop22,

    It sounds like power is shorting out or the amp is defective. With the fuse removed, use a multimeter set to ohms and check between the power terminal to ground.

    The protection light will normally come on if the amp overheats (for example when running with too low impedance), or if the speakers are shorted.

    Hope this helps.

    May 04, 2009 | US Acoustics USX-2100 Car Audio Amplifier

    1 Answer

    Amp blows the fuse every time.

    it aint the wire, the bigger the better.
    try checking your ground, if there any rust clean with sandpaper. if your gain and freq is cranked it will blow fuses and cut out, cuz the protect mode kicks in

    May 04, 2009 | US Acoustics USX-2100 Car Audio Amplifier

    1 Answer

    How many watts is it?

    85 watts
    Hope this is a fix Ya.........

    Feb 22, 2009 | US Acoustics USX-4085 Car Audio Amplifier

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