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  • New amp / whining noise when engine running

    hi forum,

    I just installed an 6 channel JL amp to power my four inboard JL speakers and two tower speakers.

    I connected both power cables (pos/neg) directly to one of the batteries.

    Sound is amazing and everything works well. Only issue is a interference (whining noise / high frequency pitch) when engine is on.

    What can be the reason / how can I fix it?

    Boat had a pre-installed 2ch amp to power a sub (both JL)
    The amp is wired to the power distributor of the boat
    I bridged the wake amp-on to use for both amp
    6ch amp is connected to the audio system by a 2ch RCA cable. Separate Sub RCA for thr sub.

    Thanks in advance for any advice!

  • #2
    Always a good idea to reach out to your equipment supplier i.e. JL audio dealer for tech support such as how and where to best connect the amp's power cables and tuning. Both these areas can lead to unwanted noise.

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    • #3
      All amps and head unit need the same power and ground source, either directly to battery or distribution block.


      Sent from my iPad using Tapatalk

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      • #4
        Originally posted by bloup101 View Post
        All amps and head unit need the same power and ground source, either directly to battery or distribution block.


        Sent from my iPad using Tapatalk
        Agreed. Most likely your issue.

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        • #5
          Originally posted by Weekendpass View Post
          Agreed. Most likely your issue.
          To be more specific:

          Run a ground wire from the battery terminal(or ground bus) directly to the back of the Head unit. Cut the ground wire from the head unit and splice it to your new ground wire.

          D2
          2002 X-Star Indmar 5.7 Vortec Predator (SOLD)
          2010 X-STAR Indmar 6.0
          sigpic

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          • #6
            Originally posted by D2Dominator View Post
            To be more specific:

            Run a ground wire from the battery terminal(or ground bus) directly to the back of the Head unit. Cut the ground wire from the head unit and splice it to your new ground wire.

            D2
            I had the same issue that you are having and I agree with D2. I went head unit to battery and it solved my problem. There is an entire thread on here about what you are going though and that’s where I got the answer, I just couldn’t find it.

            Good luck!

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            • #7
              Depending on where the head unit is located there's a short cut that will work as well. If the head unit is located in the glove box and the amps are located under the glove box like most of these boats the quick and easy way is to cut the power and ground to the radio. Splice extensions to the power and ground and route them to the power and ground going into the first amp. Loosen the power cable on the amp and insert the power cable from the head unit between the amp cable and the power cable, then re tighten the clamp. Do the same with the grounds. Since you're pulling power directly from the same source as the amps the connection has to be good.

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              • #8
                thanks for all the advice.

                I noticed there was an extra ground cable running from the audio system to the first amp already (pre-installed subwoofer amp). I added an extra ground wire to connect both amp grounds (so radio, amp1 and 2 und same ground) but this did not remove the whine (but reduced it a bit).

                As next step I think I will run the power / ground cables of anp2 to the distribution block (where radio and amp1 are connected to).

                Connecting radio to amp2 would probably just "shift" the issue to amp1 I assume (subwoofer).

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                • #9
                  Is the head unit still grounded via the factory harness?

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                  • #10
                    yes it is

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                    • #11
                      Originally posted by Lutfu View Post
                      yes it is
                      This should be modified to directly connect the head-unit ground to the same place as the amp grounds.
                      2002 X-Star Indmar 5.7 Vortec Predator (SOLD)
                      2010 X-STAR Indmar 6.0
                      sigpic

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                      • #12
                        Correction: I checked and the head unit ground is only connected to the Amp1 ground. The factory ground ends in a Deutsch connector, but does not continue). The head units power cables (red & yellow) are connect via the factory harness.

                        I added a ground cable to connect/bridge both AMPs grounds. This reduced the whining but still there.

                        Any other short cut? Or is the only option to connect the power/ground of amp2 (currently directly connected to the battery) to the distirbution block (where amp1 is connected to via factore wiring).

                        My challenge is the distribution block is quite far and I cannot access the amp1 power cables easily. Also the pre-wired gaue is not sufficient to power both amps. So before I start this let me know any other "shortcut".

                        Thanks!

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                        • #13
                          Its been said, so ill say it again. ALL audio needs to share the same POSITIVE and negative voltage source. So many forget that with 12 DC, it takes two to tango.

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                          • #14
                            just to confirm, the positive (+) cable to connect to the amp1 would be the yellow (12v constant DC). I leave the red wire (ignition) as it is?

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                            • #15
                              If the head unit harness has both red and yellow, the yellow is the constant/MEM B+.Red is switched IGN.

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