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Engine Noise in Stereo

Discussion in 'Audio' started by zcarczar, Dec 11, 2005.

  1. zcarczar

    zcarczar 1/2 ton status

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    Ok this is driving me nuts, I've spent probably 3 hours now trying to figure this out, Ive checked grounds, moved grounds, tried different RCA Cables, bypassed the crossover and I still have horrible engine noise. Anybody have any ideas? The amps are a bunch of older Harmon Kardon amps, Im running a Kenwood KVT-715DVD for the head unit and I initially thought it was the grounds for that head unit so I moved those, then the noise was still there, I checked the ground at the battery, the wire strap in the back on the firewall is ok, I also checked the grounds for the amps and those are ok also. I don't really want to run a noise filter, but I'm thinking thats what im going to have to do.
     
  2. neverendingproject

    neverendingproject 1/2 ton status

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    Are your power and ground cables close to each other? If not, its called alternator whine. I think you can get isolators from circuit city, but you will have to either pull a power to you head unit from somewhere else, or work on grounds some more (make sure they are clean). Also, it might help if you tell us what size power/ ground cables and how far they are away from your battery and ground point.

    On second thought, could be a bad amp too. :(
     
  3. zcarczar

    zcarczar 1/2 ton status

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    its definately alternator whine, I messed with it some more and unplugged the alternator while it was running and it stopped. I geuss I will leave the back seat out then and try a new amp and see if I get the noise to go away.

    I replace the head unit and the whine got worse, so I'm assuming that either my head unit is broken or I have a bad amp, but A bad amp wouldn't make sense because all 4 of the amps make the noise which I think points to the head unit.
     
  4. 81jimmyslt

    81jimmyslt 1/2 ton status

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    Do you have your RCA's and your power wire running on opposite sides. From what I've read on caraudio forum, they shouldn't cross, that can lead to noise.
     
  5. neverendingproject

    neverendingproject 1/2 ton status

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    Same with the ground wire
     
  6. Tom E

    Tom E Registered Member

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    Make sure you have a good bare metal ground for the battery and the amps. I had a similar problem once it it was solved running a larger ground cable directly to the frame for the battery and the amps. And as said before, make sure non of the wire are crossed.
     
  7. Leper

    Leper 1/2 ton status

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    Agree with most of the previous posts.
    Try running a small ground wire from radio ground to the amp ground. Make sure RCAs are not next to power or ground wires. Make sure your power and ground wires are the same size.
     
  8. chevyin

    chevyin 1/2 ton status

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    "Alternator whine" can come from many places: induced into the signal chain via the RCA cables, into the circuit via a ground loop problem, through the factory harness, etc. You need to troubleshoot and find out what's causing the problem. Bypass your entire signal chain by running an (RCA) output from a small boombox/radio to your amplifiers and see if the problem persists. If it does remain, your problem is not in the signal chain, but most likely in the wiring. If the problem goes away, you know its somewhere in that signal chain. Bypass each component individually (one at a time) including cables, until the problem goes away. Obviously this tell your the piece causing the problems. Dont forget, your headunit itself may be picking up noise via the factory wiring harness. In any serious system or one with potential noise probs, I always run a seperate ground and power wire for the headunit over from the fuse panel (and closest ground point). This bypasses the factory dash harness for the setreo completely.

    I would not recommned a 'noise filter' as they are simply a bandaide for the real problem. There is no reason you cannot build a noise-less system without bandaids in your ride, people do it every day.

    Running power and ground wires close to each other is perfectly fine, its the RCA cables carrying your signal that should be placed as far from the power and ground cables as possible, as current passing through the wire creates a magnetic field that can induce noise into the signal chain. A recent theory however is that it does not matter, because in a chassis ground the 'return' side of the circuit is the car itself, and keeping your wires far from that is well... impossible. The situation is a bit more complex than that and Im not 100% sure about that theory, but its a possibility. My point? If you are worried thats the problem (noise induced into the cables), bypass them by running another RCA outside your car (temporary) from the deck to the amps, and see if the problem goes away. If your problem is induced noise in the cables, it would go away at that point. But I doubt that's your problem honestly, as it sounds like a more acute problem. I suspect its a ground loop problem with the amps, or noise in the factory harness.

    Few ideas to get you heading in the right direction.
     
  9. zcarczar

    zcarczar 1/2 ton status

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    Ok, I just eliminated the amplifiers from being the source of my problem. I have a hunch that the head unit is causing my problems and I will have to investigate whats wrong with it but hopefully the head unit isnt damaged. I had a pioneer do the same exact crap that this unit is doing on me and it had to be sent in and repaired.
     
  10. chevyin

    chevyin 1/2 ton status

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    Its much less likely a problem with the headunit itself, and much more likely a problem with the install (wiring problem, induced noise in the signal, etc). Let us know how it works out.
     
  11. zcarczar

    zcarczar 1/2 ton status

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    I doubt its a problem with the factory wiring since it isnt there, the head unit is wired through a switch since I cant find the factory wiring anywhere for the head unit, so I rewired it using an existing switch in the dash, I highly doubt its a ground problem, the noise did not change at all when i moved the grounds for the head unit and the hideaway brain. I will check the power side when I get time.
     
  12. chevyin

    chevyin 1/2 ton status

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    You rewired it to an existing switch in the dash? What switch? Easiest place to run a power wire from to bypass the harness is from the fuse panel itself. Best place is from the battery (but you must then add your own fuse).

    Im tending to agree its probably not the wiring in the head if moving the ground did nothing (but Id still bypass the harness). Id look into the signal cable next. Run an external RCA outside the car from a source to your processor/amps and see if the noise persists.

    Again, finding noise problems is a simple matter of isolating each component in the chain one at a time until the offending piece is located. The hardest part is figuring a way to jury-rig a temporary setup to bypass certain parts of the system (like cables or the source unit).
     
  13. zcarczar

    zcarczar 1/2 ton status

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    ok, got it figured out, the head unit is bad.

    I swapped in a different head unit tonight to test it and it didnt wine with the new headunit so I kept that one installed. I will have to take the Kenwood down to the repair place though, I think its something internal to it.
     
  14. onlychevy6

    onlychevy6 1/2 ton status

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    Jason

    which truck was it? i have the same thing happen every now and again. but it is because the metal fuel lines that come up and touch the firewall by the frame then connects to the TBI unit. in the 88

    Or at least so i have been told.
     

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