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Thread: 2 way aux input switch

  1. #1
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    2 way aux input switch

    Hi Guys,

    I am new here and I searched the site for a two way switch and came up with nothing.

    My car stereo has only one input. I use it for an older XM radio that does not have a built in FM modulator. I also want to use my MP3 player, but do not want to get in an accident while unplugging the cables!

    I need a simple switch to allow me to switch from my mp3 player to the XM radio.

    The input to the switch must be female 1/8 stereo (3.5mm) and two outputs also 1/8" (3.5mm) stereo.

    I thought of building one but I am not sure that a simple switch will do and I do not want to blow the inputs of my car stereo. I think there may be some caps involved, not sure.

    Any advice, links, help?
    or maybe some schematics would be appreciated.

    found this link here:

    http://electronicsusa.com/mk1and2.html

    but i don't want to spend $21 + shipping for something as simple as this. Any suggestions?

    Cheers

  2. #2
    Car Audio Moderator durwood's Avatar
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    All you need is a switch an two standard relays, and the cables to hack apart and you are in business. Probably cost you $5-6, all you need is some wiring skills. Let me find or make a picture.

  3. #3
    Car Audio Moderator durwood's Avatar
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    If you want a really simple method, but you might a slight leakage of sound from one source to another, Use a 4 Pole Double Throw Switch (4PDT). Just connect the ground signals together and wire the signal wire to each Pole of the switch.

  4. #4
    Car Audio Moderator durwood's Avatar
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    Here is probably the best way to do it.
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  5. #5
    Constant Bitrate
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    Good idea.. can you make it better?

    Quote Originally Posted by durwood View Post
    Here is probably the best way to do it.
    Now if you could add some way to have the Mute sensor activate it, I would solve one of My problems!



    Jonathan
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  6. #6
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    Re: 2 way aux input switch

    Thanks for all your help guys.

    I used a regular 4PDT and it works, and no noise on the line.

    I was curious to know why other audio switches (and one Radio Shack video switch in particular) that I have is a bit different. Being a bit curious, I opened it up and checked it out.

    The video switch is a 3 input (RCA jack) into one TV.

    It is just simple 3 way switch except that it has 47K resistors across the inputs + and - (only on the audio, nothing on the video) I am GUESSING that when the input is unused the resistor pulls the input low to eliminate noise on the line??????

    There are no other components on this board other than the resistors and the switch itself.

    Cheers

  7. #7
    Car Audio Moderator durwood's Avatar
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    Quote Originally Posted by SEGgeek View Post
    Now if you could add some way to have the Mute sensor activate it, I would solve one of My problems!



    Jonathan
    Mute sensor from what exactly? Is it a simple momentary button? Is it a 12V trigger or ground trigger? Let me know and I will update the diagram for that too.

    I am GUESSING that when the input is unused the resistor pulls the input low to eliminate noise on the line??????
    Yes you are correct, it's probably either for impedance matching or to help reduce nosie. If just the switch works for you then you are set. No need for additional parts.

  8. #8
    Low Bitrate
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    I would actually recommend using one more rely to switch the grounds seperatly. that will lessen chances of outside noise. i have the same setup in my truck

  9. #9
    Variable Bitrate 3g Jester's Avatar
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    Well im kind of trying to do the same thing. To be honest the radio sucks. theres rarely any good stations. so i have my Carputer and i have my sirius. i want to keep them seperate..sometimes i am on a short trip where i just want some good radio instead of waiting for my puter to boot. Soooo... i went looking for a 2 RCA IN to 1 RCA out. that way i could use the single RCA in on the back of my headunit. The sirius reciever has an FM modulator but to be honest it sucks. If there is any kind of radio station..even slight fuzz near that freq. it sounds like ***. and it doesnt come in as crisp or as loud or as clear as when its hard wired in.

    so i went looking for my RCA spliter with a switch and i couldnt find anything i like. either way to big or it came with video too or....just nothing i would want to or could mount (cleanly) to provide the switchability.


    DURWOOD.....thank you!!!! im going to go get some relays and try my hand out at building that little doozy of a toy you posted up. that way i will get to have my one tiny little switch!!! and no ugly boxes or anything

    Any guidance on what type of relays to get though?

  10. #10
    Car Audio Moderator durwood's Avatar
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    Any 12V relay would do. They are available at any auto parts store. You can find smaller ones too, but these are easy to find. Something like this.

    http://www.partsexpress.com/pe/showd...number=330-070

    Also, you can add in another relay for the ground wires too as tdub24 suggested, although it may or may not be needed. Depends on if you have noise.

    Also, somethign I left out. It's good practive to insert a diode between leads 86 and 85. For more info on relays visit

    www.the12volt.com
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