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Thread: Alternator whine and other noise problems.

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    Alternator whine and other noise problems.

    I am at my wits end trying to solve system noise issues. I am dealing with 3 separate problems that all cropped up at the same time. I have a new alternator whine, a low rumbling static like sound, and system hiss that all cropped up when I installed a DSP into my system.

    Background:

    I received a Dayton DSP-408 for my birthday last week. Got it installed 5 days ago and have been chasing noise ever since.

    my old setup that was noise free was a older pioneer hu into a PG tantrum 600.4 with two channels feeding front passives and two channels bridged to my sub. Being a single amp system I had the power and ground wires direct to the amp, no distribution blocks needed.

    My new setup is Hu to DSP-408 using the same 2 pairs of rca cables that i already had in place. from the dsp I have 2 new short rcas to the old PG amp. added a third set to a MTX thunder ta202 to power my tweeters. I re used the same power and ground cables by running them into distribution blocks and than ran new power and ground wires from there to both amps plus the dsp.

    after installing I keyed on the system and I immediately noticed a system hiss and a low rumble sound coming from my door woofers and my sub. after lowering the main volume on the dsp I got the hiss to a manageable level and after some experimenting I found that the rumble only occurs when I have my HU set to disc. it does not make the noise when using the tuner or aux input. I initially thought it was no big deal because I use my aux in 90% of the time.

    After finishing a basic set up of the DSP i finally started the engine and than I was greeted by a very loud whining noise. as a temporary band-aid I was able to lower the main volume on the dsp another 20 points to get it to the point of minor annoyance as opposed to piercingly shrill.

    Things that I have tried to isolate or eliminate the noise:

    I replaced the factory ground cable from the battery to the chassis with a much larger wire. no change.

    Ran a new dedicated ground from the battery to the HU. Made the noise worse.

    ran a temporary connection from the oem radio ground wire the the HU chassis. The noise got slightly better.

    Removed the oem ground and the direct to battery ground and installed a ground wire from the HU to my distribution block so everything in the system has a common ground. noise is the same as it was running the oem radio ground but better than it was running a ground wire direct to the battery.

    tried testing the system with the HU out of the dash and resting on my knee. no change.

    I tried disconnecting the rcas from the back of the HU to see if I was picking up noise in the cables. with the system powered up and the rcas connected to the dsp but not the HU my alternator whine is gone but my noise floor hiss is still present.

    Tried swapping to an old Kenwood HU that I had sitting around. Noise is unchanged.

    I double checked and freshly sanded my ground point in the trunk to see if that would help. No change to the noise.

    The last thing I can think of to try is looking for a different part of the chassis to ground my distribution block which I am going to attempt later today.

    If that fails than the only other things I can think of would be to add some dedicated ground cables for the alternator housing and the engine block to see if somehow i have a week factory ground causing an issue underhood, pulling a A/C ripple wave form on the charging system under load, or ordering a set of ground loop isolators like these https://www.crutchfield.com/p_127SNI1/PAC-SNI-1.html

    now that I have a taste of what a fully active system can do I do not want to go back to passives again but these noise problems are killing me.

    Any tips or suggestions would be very appreciated.

  2. Back To Top    #2
    Owner BigAl205's Avatar
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    Alan
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    Re: Alternator whine and other noise problems.

    The only additional troubleshooting ideas I can come up with is to run a temporary ground wire from the HU back to where the amps and DSP is grounded. You may also try running RCA's across the top of the carpet directly from the HU to the DSP to see if it's maybe picking up something along the way. Last idea is to wrap a wire around the RCA shield at the HU and grounding it. I was thinking it could be a pico fuse inside the Pioneer, but you said you tried a Kenwood, so that eliminates it as a suspect...unless you have multiple issues.

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    BURNED OUT Hillbilly SQ's Avatar
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    Chris
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    Re: Alternator whine and other noise problems.

    What kind of rca's are you running? I prefer shielded cables in a standard unbalanced setup.
    They might say "don't try this at home" but nothing about not trying it at your friend's house.

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    Re: Alternator whine and other noise problems.

    Currently I have the head unit grounded to the same point as the amps and dsp. no joy from that change.

    i am running a mixed pair of rcas. one is a twisted pair the other is a coaxial type. beyond that i dont know much about rca cables but i can google it and see if i can provide more details if needed.

    I will go digging to see if i can scrounge up a long enough rca to try a test run across the cabin.

    one thing that has crossed my mind more than once is could i have a faulty dsp? I know the dayton units are not as nice as say a helix or what not and i have read that some people have noise problems with them. I just don't like to jump right to condemning a brand new part unless I can prove it is bad.

    thanks for the replies gentleman. I will try some more things asap and get back with the results.

  5. Back To Top    #5

    Re: Alternator whine and other noise problems.

    Just finished another round of testing. Tried grounding the outer rca ring to the HU. No change.

    Ran another rca from the HU to the dsp across the seats. No change.

    Unplugged the antenna lead. No change.

    checked the alternator ouput. Found i am holding 14.1 volts at the battery under standard load (high beams, A/C on etc...) with 27mV ac ripple through the diode tree.

  6. Back To Top    #6

    Re: Alternator whine and other noise problems.

    Are you using the Dayton master volume controller? Heard they can be noisy.


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    Re: Alternator whine and other noise problems.

    No on the wired remote controller and yes on the bluetooth adapter. and just in case it matters the noise is the same with and without the BT dongle installed.

    As another test I ran an extension cord out to the car and powered the DSP off of the supplied 110v adapter with the 12v in fuse removed. No change in the noise.

    The only thing I have found that seems to eliminate the noise is to unplug the rcas from either the HU output or the dsp input.

    As far as I can tell the noise is not present when the rcas are disconnected and I am streaming BT audio direct to the dsp.

    Would it be possible that I have had a problem all along but it was masked by the passive crossovers? that is one way I could explain why I have noise issues on a previously noise free system but I have no clue if that is even possible.

  8. Back To Top    #8

    Re: Alternator whine and other noise problems.

    Could be - are you able to change the RCA’s from the headunit to the DSP to confirm?


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  9. Back To Top    #9

    Re: Alternator whine and other noise problems.

    I have tried a spare set of rca cables. noise unchanged. at this point i am seriously considering ordering a set of ground loop isolators. after reviewing the different kinds of rca cables available I will try and check all of my gear to see if they are single ended or differential inputs and maybe will try ordering some new rcas of the correct type as needed.

    from what I gathered looking at the owners manual last night it seems implied that my PG amp uses differential inputs. I am going to guess that my mtx amp and my dsp us single ended inputs. if I can prove that to be the case than maybe swapping from twisted pair style to a set of shielded coaxial rcas may be of use for some of my gear.

  10. Back To Top    #10
    Owner BigAl205's Avatar
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    Alan
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    Hayden, AL
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    2018 Chevy Silverado Z-71
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    5,699
    Join Date
    Feb 2013

    Re: Alternator whine and other noise problems.

    Disconnect the input on the DSP and see if the problem continues. If so, disconnect the DSP output. If the problem goes away, it's definitely the DSP. If not, keep going down the chain until it goes away.

    ...process of elimination....

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