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New amp buzzing

Discussion in 'Gen 3 Prius Audio and Electronics' started by vash2695, Mar 8, 2020.

  1. vash2695

    vash2695 New Member

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    So I just installed an aftermarket amplifier in my 2010 Prius and have an issue with a buzzing noise. I've tested almost everything I can think of to no avail.

    The buzzing never changes in tone or volume, it is constant. It does not occur if the inputs of the amp are unplugged, but starts immediately if I hold a small RCA cable while grounding myself to the vehicle. I've moved my ground wire to different spots in the car (no change), I moved the power cable away from the hybrid battery (no change). I've also tried connecting RCA cables with their ground removed, and connected that to my head unit, and I still get the noise.

    The noise will not occur if the car is off, but starts immediately if the car is either on or in accessory mode. After powering off the car, the noise will persist for about 5-10 seconds.

    I have a feeling that this may be a wiring fault with another component of the car, but have no idea what I can do to determine which one it is. No other modifications have been made to the car, only the amp and an aftermarket head unit. The amp is located in the dash.

    Please help!

     
  2. Grit

    Grit Senior Member

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    Are you rca cables running parallel with a 12v source?
     
  3. ccaudio1

    ccaudio1 Member

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    What brand amp are you using?

    I ran across a similar issue with my V.

    I use install sound system for work so I did everything that I know off to get rid of the noise.

    Bottom line was the amp built in filters were the issue.

    Initial amp was planet audio but switched to diamond audio - which the noise disappeared when the diamond was installed.

    Posted via the PriusChat mobile app.
     
  4. ChapmanF

    ChapmanF Senior Member

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    When I added an aux input on my Gen 1, I had to add one of these.

    In my Gen 3, if I remember the diagram right, the cabling from the headunit to the JBL amp under the seat is shielded, the shield is unterminated on one end (and this seems to be deliberate) while the other end terminates on a dedicated connector pin, not just chassis ground; I think there is an isolated audio ground that is not the chassis power ground.
     
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  5. Ed Beaty

    Ed Beaty Active Member

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    [you are a dang wizard, Chap...]
     
  6. vash2695

    vash2695 New Member

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    I am not sure what you mean here, but I have wired everything (as far as I know) in a standard configuration.

    I did consider testing with a different amp, I probably will if all else fails. The amp is an NVX VADM4. I've looked around and have not seen any other reports of a similar issue.

    Mine only had the base system. I do have the fuse for the JBL system, but I doubt they would have the wires in place, though if I could find some sort of diagram showing me the cable routing I may be able to figure it out. As far as filtration goes, I believe if it were a simple grounding issue, then moving the ground or the point that is contacting the input (like connecting the ground of the RCA to different parts of the car) would result in at least SOME change in the noise. This seems to be exactly the same regardless of location. I also tested using only the positive lead on the RCA and still got the same result. And as a final note, this still occurs even when the ground is attached directly to the amp.

    Would anyone know if a ground loop could possibly occur conditionally? IE with vehicle on vs off?


    My current running theory is that SOME electrical component has a short to ground or some other wiring fault, which in turn is leaking noise into the entire system (maybe DC-DC converter, but I'm not sure if that is utilized when the system is in ACC mode, as the 12v aux battery is not being charged until the car is running). I checked OBD2 codes and everything looks fine, and there is no phantom power draw.
     
  7. ChapmanF

    ChapmanF Senior Member

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    My story would be that the ground loop is always there, but the signals being coupled onto it are stronger when the car's electronics are active.
     
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  8. vash2695

    vash2695 New Member

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    Ok, as far as I know there are a few options to eliminate ground loops. One would be to ground the RCA cables directly, correct? If so, I've tested that and had no luck, but if it does work differently then I'll definitely try it.
     
  9. vash2695

    vash2695 New Member

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    Update: I was mistaken on the concept of ground loop isolators. I previously believed that these simply functioned as an additional grounding point, but they actually seem to function via induction, which means no physical connection should be involved (though not all may function this way). If this is correct, then this should theoretically solve my issue, as there are no issues when the inputs are unplugged. I'll get them and report back!
     
  10. vash2695

    vash2695 New Member

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    Huzzah! The ground loop isolators did the trick! I feel dumb for not knowing how ground loop isolators actually functioned, but now I've been able to set my gain where I want it and can only hear the slightest bit of noise. Also, should anyone else do a similar setup to mine, I noticed something with the android head unit that I have. If you use the "Loud" mode in the EQ options, you will get significantly higher hiss when audio is playing. Turning this off will reduce that dramatically (and the response curve is much more flat). This should apply to most units currently on the market.