Question Amp power and speaker issue

Discussion in 'ICE, Sat Navs & Dash Cams Forum' started by Netskee, Apr 14, 2016.

  1. Netskee

    Netskee
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    Hi all

    I've installed a nexus 7 into my car and have a alpine ktp-445u hooked up to a Bluetooth audio recieved to play my music. The situation I've got is that I bought a harness to connect from an after market head unit into my cars wiring. I chopped the wires that would go into the head unit and connected them directly to the amp.
    1st problem lies here.. As it goes direct to the amp, the remote turn on didn't work, so I've had to wire the remote to the constant feed but this is no good as it's drained my battery. I've thought about adding a switch to turn it on and off but I don't like the idea of that so was wondering if anyone has any suggestions I could try?

    2nd issue is, when there is no music being played, the speakers make a hissing noise (like when the volume is cranked right up) any thoughts on this?

    Thanks
     
  2. edd666999

    edd666999
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    The harness you bought to take your car wiring into standard iso will have both a live and a switched live, this is where you can usually get your remote.

    Maybe grab a photo?

    The hissing to me would suggest the Bluetooth receiver or possibly the quality of connector used with it.
     
  3. Netskee

    Netskee
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    I'll try get a photo over the weekend. I had the harness all plugged direct to the car but like that, the amp would not power up. I've had a thought and maybe taking a live feed from the 12v socket would work as that powers down after like 15 mins?

    Yeah I see what u mean. I may try using an audio cable direct into the amp and just do away with the receiver
     
  4. edd666999

    edd666999
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    That wiring harness is all you need, Get me a photo and im sure I can point you in the right direction :)
     
  5. Netskee

    Netskee
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    So over the weekend I tapped into the 12v socket and it works perfectly. Only problem I have now is the hissing noise. As soon as the amp receives power (when the cars unlocked and 15 mins after I lock it) it starts up. As soon as music is played it's fine. Even if I have a track on with no volume it's ok. As soon as no audio output is received, it starts up. May sound trivial but it's driving me nuts!
    Any ideas?
     
  6. edd666999

    edd666999
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    Well the device receives the volume level from the bluetooth connection, maybe its on 100% all the time with no connection?
     
  7. Netskee

    Netskee
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    Wouldn't have thought so? Even if I pause a track it does it. I'm not using Bluetooth any more either. Just an audio cable from the headphone port
     
  8. edd666999

    edd666999
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    straight into the amp?
     
  9. Netskee

    Netskee
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    Into a 3.5 to rca then to the amp
     
  10. blankscreen

    blankscreen
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    My 2p's worth, why not simply by a conversion loom?

    if you have no input loading to the amp it will hiss, this is different to having no signal during quiet sections in music, or program/CD being paused.

    Think of having a simple guitar amp, with the input lead plugged into the amp but not a guitar (or other instrument) perhaps due to the cable being severed, you then have an 'open (or unloaded) input'.

    Signal Inputs to amps are very sensitive often quoted as an impedance figure. in simple terms this impedance 'loads' the amp's input, which then ignores higher impedance signal sources such as RFI and so silences your hisses.

    the above is not intended to be tectbook technically exact, but as a laymans guidance.

    i think likely your amp is left 'live' and so input wide open by whatever is connected to it, it is being disconnected via your wiring modifications.

    Alan
     

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