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getting around factory amp issue

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  • getting around factory amp issue

    here's my situation, my particular car needs the factory amp because the navigation phone and all the other bells and whistles run through it. I'm upgrading my system and really don't want the factory amp but I want my music to attenuate the same way when the phone call comes in or the voice navigation comes on. So what I'm thinking about doing is taking the speaker lines that come out of the head unit and go into the factory amp and route that to a junction box (I'll get back to this) then out of that directly to my aftermarket amp. Then taking the line out of the factory amp that would go to the speaker, and send that to the junction box. In this box I'm imagining something that will see (audio) voltage from the factory amp carrying the phone signal, navigation, and any other voice directive coming from the car. when it sees that voltage it attenuates the main audio signal coming from the headunit and patches the phone or whatever else in.
    Here's the question, what do I need besides a relay to build something like this? Where to begin? Will this work?

  • #2
    Could something like this work for your install? SNO


    • #3
      Sort of, but I think id need to build it because I need

      1/ 4ch unbalanced in for ch 1
      2/ 2ch unbalanced in for ch 2
      3/ 4ch unbalanced out
      4/ no time delay.

      Unless you know of one that does what I need.


      • #4
        does somethong like that have a specific name?


        • #5
          This is also from the same company. It has 4 channel connections. Not sure if you can find one, they seem to be sold out everywhere. SNO


          • #6
            You are right, they are either sold out or discontinued. So I need to make something. Problem is, when thinking on how I would make this, I realise that everytime the relay would switch audio to gps voice I would probably get a pop in the speaker when switchng sources. So Im now thinking an attenuator activated by a relay acting on the music signal would be the best route. Here is what I drew up on how I imagine it. Can someone tell me what components to buy to build this, or if something like this already exists?


            • #7
              Gang a couple of these together:

              link to my CTS-V project:



              • #8
                That looks good. The question is, have you used that? Because remember, my issue now in thinking of the mechanics of this is, there will probably be a pop in the speakers everytime it switches over. That's why I changed to looking towards attenuation of the music instead of switching. So do you have personal experience?


                • #9
                  If you don't want a pop, get a relay and short the input lines whenever there is a switching action.

                  A lot of the newer switches use fet switching so you don't get pops.

                  I HAVE NOT USED THE ITEM.
                  link to my CTS-V project:



                  • #10
                    Ok. Do you think it would be possible to show me how to make this with this relay and short? I kind of still have my heart set on attenuation of the music, but if that's not possible I'd rather give a shot at making this relay device instead of buying one. Could probably do it for less than half the cost of that and get an education out of it.


                    • #11
                      When you add up the shipping and handling buying parts from Digi-Key or Mouser, and the time, it is better (IMO) to buy something that works and adapt it, rather then re-invent the wheel.

                      All you have to do short out the input lines and that will mute the sound.

                      If you add a resistor, you can attenuate so it doesn't go dead silent.

                      On a 10k input I would try a 250 ohm load and see how much that drops the sound.

                      The device I gave you a link to will do two lines.

                      Add another one to do the four.

                      It even has a 12 volt trigger and I bet it doesn't
                      "pop" when switching either.

                      Here is a device to look at:


                      What exactly are you trying to do?

                      Do you want to "bleed" the GPS voice commands over the normal audio?

                      I would just switch the inputs (FET) and give the GPS priority.
                      Last edited by heavymetals; 04-03-2013, 11:01 PM.
                      link to my CTS-V project:



                      • #12
                        Originally posted by heavymetals View Post
                        that's really going to be the easiest way to accomplish what you want to do. $100 for a complete setup is really quite good.. of course it ruins the diy stuff, but i really don't think you could come in that low diying a solution..

                        those units are a little tricky to setup to switch at the right times-- i did a niles amp in a conference room once with an identical feature(they wanted the background music to play through unless there was a conference call/video meeting)--but once they are setup, they don't need to be touched again..
                        My OLD 2001 Mitsubishi Eclipse GT:
                        "The Project That Never Ended, until it did"

                        next project? subaru brz
                        carpc undecided


                        • #13


                          • #14
                            Originally posted by Champak View Post
                            What did you end up doing?
                            link to my CTS-V project:



                            • #15
                              I haven't done it yet because there are a few other things I have to do to the car, but I'm going to follow your suggestions and get one of those devices instead of building one.