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Bad static from tablet and speakers - need help, please!

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  • Bad static from tablet and speakers - need help, please!

    I have Samsung Galaxy 2 (7.0") installed in my truck, bought Alpine amp KTP-445U and upgraded the speakers. Best Buy did the install.
    Here are 2 problems:
    1. Huge static when the nothing is playing on the tablet. I actually have to play something and just mute it so that I can talk on the phone.
    The tablet is hardwired now. Any idea what should I do?
    2. When I unplug the power from the tablet the sound stops coming from 3.5mm to speakers. Music is only playing on the tablet. This is crazy!

    Please help, I'm lost here.

  • #2
    Just checked, but took off the power from hard wire and just used cigarette adapter, no difference.

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    • #3
      I have the exact same amp and love it. In my system it is whisper quiet with nothing playing. This is a very quiet class D amplifier and has one of the best signal to noise ratios in its class. Just from the description, I would probably say it is some sort of grounding issue. Without seeing the install, it might be hard to diagnose. Did they hook it up via the speaker level inputs or did they use a 3.5 to RCA adapter? If they did use the RCA inputs, do you know if they used the 2 small silver ground loop isolator boxes that came with the amp? If the amp is viewable where they installed it, take a look and let me know. I installed car audio professionally for nearly 20 years. I've seen some pretty horrible installs done by Best Buy. When I ran an install shop, a problem like that would never have been allowed to leave the shop.

      I am a little unclear about something. You said you removed the 3.5 "power" plug from the tablet and the sound started coming from just the speaker in the tablet? That sounds like you unplugged the headphone jack.

      Is the noise static or a whining sound? Does it change when the engine is running? Also, if you have a different audio source like an Ipod, try plugging the headphone plug into it instead of the tablet and see what happens.
      Last edited by XSiveJeff; 02-14-2013, 03:52 AM.

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      • #4
        on the noise issue...

        agree with XSiveJeff - how is the headphone jack being hooked to the amp exactly? also:

        - does the noise happen if the 3.5mm plug is completely removed from the tablet and not touching anything?
        - try unhooking the inputs from the amp, see if the static persists (likely not)

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        • #5
          Originally posted by XSiveJeff View Post
          Did they hook it up via the speaker level inputs or did they use a 3.5 to RCA adapter? If they did use the RCA inputs, do you know if they used the 2 small silver ground loop isolator boxes that came with the amp? If the amp is viewable where they installed it, take a look and let me know. I installed car audio professionally for nearly 20 years. I've seen some pretty horrible installs done by Best Buy. When I ran an install shop, a problem like that would never have been allowed to leave the shop.
          They used 3.5 to RCA adapter. I don't see any silver boxes there. But I did just turn the GAIN on the amp way down/off, and the sound went away.
          Originally posted by XSiveJeff View Post
          I am a little unclear about something. You said you removed the 3.5 "power" plug from the tablet and the sound started coming from just the speaker in the tablet? That sounds like you unplugged the headphone jack.
          Is the noise static or a whining sound? Does it change when the engine is running? Also, if you have a different audio source like an Ipod, try plugging the headphone plug into it instead of the tablet and see what happens.
          No, I said when I unplug the power cable the sound from the speakers disappears. So, even though the 3.5 to RCA is still plugged in, the sound only comes on tablet speaker. I guess it's not that big of a problem since it's always powered on, but just weird.

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          • #6
            I do have another question. What do you guys use for power apps? I want the tablet's screen to go off when I turn off the truck and on when I turn it on.
            The system setting don't do any of this, I tried some apps but don't see anything like this.
            What do you use?

            Comment


            • #7
              Try Caffeine https://play.google.com/store/apps/d...ntaxa.caffeine
              You will need to wire the power for your tablet into the Accessories power line of your car though.

              I can't really follow what your noise issue is, but if you can connect your tablet to your amp or stereo via bluetooth, it should be an easy way of get rid of any ground loops.
              Last edited by badmonkey23; 02-16-2013, 09:10 PM. Reason: Link to wrong Caffeine app
              Android Tablet In-Car Sliding Dock using hacked DVD drive

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              • #8
                Ok.... That amp does come with 2 really nice loop isolators in the box. Maybe they just kept them. The headphone jack output shares a ground between both channels and I believe the amps input grounds are floating. Going direct from the headphone jack to the amp input shorts the left and right channel grounds together which might be the cause of the noise if they left off the isolators. The amps inputs use a floating ground because most factory stereos have floating ground outputs. In most quality amps, the signal grounds stay isolated from each other and from chassis ground.

                As far as the sound from the amp going away when you pull the power plug.... it's because they used the current sensing turn on feature of the amp. Power runs through the amp to get to the tablet. When there is a current draw, ie. the tablet draws external power, the amp senses it and turns on. No current draw, no amp turn on. It was designed so it could be used with a factory stereo that has no amp turn on output.

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                • #9
                  XSiveJeff, thanks for the help! Took the truck back to Best Buy, they installed it, no noise at all now!

                  badmonkey23, gonna try this app today, will post.

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                  • #10
                    Originally posted by badmonkey23 View Post
                    Try Caffeine https://play.google.com/store/apps/d...ntaxa.caffeine
                    You will need to wire the power for your tablet into the Accessories power line of your car though.
                    I don't see an option to go off when the power is absent, is it not there?

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