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How to bypass headunit using stock amps

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  • How to bypass headunit using stock amps

    I want to make my carputer replace my head unit. My car is a Ford Probe GT with premium sound and as I understand it has a stock amplifier after the head unit. I just need to know how to hack up some RCA cables (minijack to RCA from my line out on the soundcard) in order to make them go to the 4 speaker + and - wires on the wiring harness. Like when I cut off the RCA plugs, how many wires will be in there and which will be the + and which will be the - ?

    And also, since there is only 2 RCA plugs coming out of the computer (white and red) how will I make it go out to 4 speaker + and - wires on the harness (8 total connections to be made) since there will only be probably 4 wires coming from the RCA, 2 for each channel?

    I hope this makes some sense and somebody out there can help me out.

  • #2
    I'd get a soundcard that can handle the number of channels your pumping to. I wouldn't cut any RCA cables up, just get some mini to RCA cables from radio shack.

    FYI, you're the seccond person to ask about this in the last couple of hours. Look arround a little bit more and you'll find lots of answers.

    Rob
    car computer rev 5: 8" lilliput and usual suspects

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    • #3
      Originally posted by robiewp
      I'd get a soundcard that can handle the number of channels your pumping to. I wouldn't cut any RCA cables up, just get some mini to RCA cables from radio shack.

      FYI, you're the seccond person to ask about this in the last couple of hours. Look arround a little bit more and you'll find lots of answers.

      Rob
      The thing is that I don't even know if my stock amp would have RCA inputs... would it? If not then my only options are to use an aftermarket amp or to cut up the RCA cable. I just want to know what an RCA cable is composed of, is it just 2 wires per channel or what?

      BTW, I would be using mini to RCA cable but just cutting the RCA ends off.

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      • #4
        Originally posted by Bobby Digital
        The thing is that I don't even know if my stock amp would have RCA inputs... would it? If not then my only options are to use an aftermarket amp or to cut up the RCA cable. I just want to know what an RCA cable is composed of, is it just 2 wires per channel or what?

        BTW, I would be using mini to RCA cable but just cutting the RCA ends off.

        From what I understand, you cannot just simply cut your RCAs and connect them to your amp input wires (unless you have RCA inputs), as RCAs are low level lines and speaker wires and high level lines.

        I was looking into this a while back and there are a few low level to high level converters but they are fairly $$. Somebody correct me if I am wrong here, but this is what I understood.
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        • #5
          Originally posted by Bobby Digital
          I want to make my carputer replace my head unit. My car is a Ford Probe GT with premium sound and as I understand it has a stock amplifier after the head unit. I just need to know how to hack up some RCA cables (minijack to RCA from my line out on the soundcard) in order to make them go to the 4 speaker + and - wires on the wiring harness. Like when I cut off the RCA plugs, how many wires will be in there and which will be the + and which will be the - ?

          And also, since there is only 2 RCA plugs coming out of the computer (white and red) how will I make it go out to 4 speaker + and - wires on the harness (8 total connections to be made) since there will only be probably 4 wires coming from the RCA, 2 for each channel?

          I hope this makes some sense and somebody out there can help me out.
          You might want to keep in mind that it's rare to have true surround sound in a car. It's a BIG distraction, and difficult to get "tuned" in properly anyhow. Your basic headunit will take two channels and split them accordingly. I would suggest digging in and getting a good look at that amp. If it has RCA inputs, great! Feed it direct from the carPC and listen to the music! If not, then you are likely dealing with something proprietary, in which case you would be better off just spending a little dough and buying an aftermarket amp to power the speakers. Some amplifiers accept left/right input, and split each channel to feed front/rear speakers. If you ARE looking for surround sound, then I would recommend a pair of amps. Feed one with front channel information, and the other with rear.
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          • #6
            hey...i have a ford as well, and the seperate amp ur talkin about does not have rca inputs. it takes the speaker output from the head unit which is already amplified and the seperate amplifier amplifies the sound even more from there. you could hook up ur computer sound out to that seperate stock amp, but the sound will not be anywhere near as loud as coming from your head unit. if you're using a good ol soundblaster as your sound card, usually u'll have an output which is amplified by the card's onboard amplifier. that will definately work better than just line out to that other amp, but it still won't be as loud as from the head unit as the soundblaster's amplifier puts out something like 4 watts into an 8ohm speaker. you qould also hafta chop a cable which has a 1/8" stereo jack on the end of it. also as was said before, surround sound in the car is a pain, so you could hook up the cable to the amp as the head unit does: left channel out goes to the front and back left channel inputs, and the same thing w/ the right channel. also, since ur head unit is a stock ford head unit, i'm 99.9% sure it won't have any kinda aux inputs of any kind on it, unless it supports a cd changer. so basically....get a head unit w/ an aux input (like a pioneer that supports a cd changer or a jvc w/ a 1/8" stereo input jack) and that'll make life a whole lot simpler.
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            • #7
              I am having the same "problem" with a Monsoon system in a Passat. What I will try to do is hook up an amp output the input of the stck crossover amp.

              Cheers,

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              • #8
                Ditch your head unit and buy an inexpensive (~$150) 4 channel amp and an Audigy card ($75). Then you can output from your sound card (front R/L, rear R/L) right to the amp. Get another 2 channel amp if you want/have more speakers. The Audigy software lets you set up and tune any combo of channels and speakers (4.1, 5.1, 6.1).
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                • #9
                  I am ditching the head unit. The problem is that with monsoon systems you have 4 tweeters and 4 subs, 2 on each door and hte stock amp/crossover sends the appropriate frequency to each speaker.

                  I think its easier to use an amp and send speaker level input to the stock amp/crossover.

                  Cheers,

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                  • #10
                    Originally posted by Bobby Digital
                    The thing is that I don't even know if my stock amp would have RCA inputs... would it?
                    why don't you tell us? if your car were in my driveway I'd go out and look at it
                    car computer rev 5: 8" lilliput and usual suspects

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                    • #11
                      just a note on stock amps.... In case this wasn't said before, if you want to get your factory amp to turn on, you will have to identify the lead coming from your factory deck that is sending 12v to the amp(just like remote on aftmrkt amp) and you will have to supply 12v here since you are removing the factory deck... The factory deck is likely a preamp although I'm not too familiar with fords so I'm not sure... After you find out where to supply power to turn it on, you can test which inputs to the amp correspond to which speaker... the factory amp is likely a four channel amp.... I have done this on other cars and plan to do this on my 99 Lex GS300 in order to reduce clutter(extra amp)....

                      If all this sounds like too much, find the cheapest quality deck with aux-in and have best buy install it(look for free installation deals)... Then install the pc with a y adapter 1/8in headphone jack(from soundcard) to rca(to aux-in on deck)...
                      good luck

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                      • #12
                        oh yeah and you probably don't have rca inputs on the fact amp... you'll have to add this... get some rca terminals at radioshack(or online if u can wait)... You'll see that each rca consists of two leads...... You just have to find out which leads coming from the factory harness go to each rca.. i have a trick with a battery but I won't be responsible for your blown speakers or ears.....

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                        • #13
                          Originally posted by A_C_K
                          oh yeah and you probably don't have rca inputs on the fact amp... you'll have to add this... get some rca terminals at radioshack(or online if u can wait)... You'll see that each rca consists of two leads...... You just have to find out which leads coming from the factory harness go to each rca.. i have a trick with a battery but I won't be responsible for your blown speakers or ears.....
                          maybe reading the whole topic isn't such a bad idea. A rather important point was brought up: for the most part, factory headunits are outputing, say, 15watts on each channel. The 'premium' amp is designed to take that level input, not the low level signal provided by a computer, or generally on RCA cables. It may not have been the case in your setup, but it was in my car, (ended up replacing everything), and from other's posts it's almost universally the case with stock 'premium' systems.
                          car computer rev 5: 8" lilliput and usual suspects

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                          • #14
                            Originally posted by robiewp
                            maybe reading the whole topic isn't such a bad idea. A rather important point was brought up: for the most part, factory headunits are outputing, say, 15watts on each channel. The 'premium' amp is designed to take that level input, not the low level signal provided by a computer, or generally on RCA cables. It may not have been the case in your setup, but it was in my car, (ended up replacing everything), and from other's posts it's almost universally the case with stock 'premium' systems.
                            So anywhere we can get sheap, quality product that amplifies stereo out from teh carputer to match amp?
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                            • #15
                              better yet, get yourself an USB sound card with RCA connectors for the output, and you can connect straight to the amps (Creative MP3+ USB works like a champ in my setup)
                              Also, this will avoid the mini-jack to disconnects itself with the vibrations of the road (the springy effect on those mini-jacks is terrible)
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