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Thread: directly wiring sound into stereo... anyone REALLY good?

  1. #1
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    directly wiring sound into stereo... anyone REALLY good?

    I have a shop manual for my car, which includes wiring schematics for the whole stereo, by looking at them, could anyone come up with a way to tap into it other than an FM modulator or tape deck thing?

    if it makes it easier, its a Bose sound unit, with a seperate amp, and a second subwoofer amp. woud the line going from the head to the first amp, would that have R/L lines that I could just splice into with the sound card outs? then hook them both into a switch and just alternate between which input it plays? possible or no?

    I can send pictures of the schematics if that will help someone to help me, but I have no where to host them so itd have to be by email or aol IM...

  2. #2
    I'm sorry, and you are....? frodobaggins's Avatar
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    possible, only one way to find out..
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  3. #3
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    trying to make sense of it... and this is what Ive found, theres inputs into the head unit which it calls "navi input (-)" and "navi input (+)" and on the actual line it says W/B and L/B, there is also a "navi ground" along with a "navi on" they are 4 plugs on the back.

    any way this can happen with these?

    then going to the amp, it has 2 lines (+ and -) for each of the speakers... which totals to 4 pairs of wires(2 pair for front speakers, which after the amp split to control door speakers and tweeters, and the other 2pairs do the rear speakers) for a total of 6 speakers. plus anothe 2 for the subwoofer...

    to me, the uninformed, it would seem there is no good place to splice into it after the headunit...

  4. #4
    Raw Wave Rob Withey's Avatar
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    Feel free to mail them my way and I'll take a look (rob_withey@hotmail.com). I hacked into my headunit a while back with no schematics to add an aux in. Details on my site.


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  5. #5
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    I am currently working on the same concept. The only difference is that I intend to remove my head unit compeltely, and drive the amp with the soundcard alone. It can be done, but it has gotten a little out of hand for my case. Let me fill you in.

    First, I never had any diagrams or schematics of the radio, so I was working blind. The car is a chrysler, so the sound system is an Infinity system. It includes a headunit (HU), with 4 pairs running to an amp in the trunk, which then drives 6 or 8 speakers (can remember, but it does not matter). Again, i was going to remove the headunit, and drive the amp with the sound card.

    What you need to be aware of, are signal levels. For example, the signal 'power' or 'level' coming out of a headphone jack, or in this case, a sound card spkr out, is called Line Level. This is just about the lowest power signal we are going to deal with. It will not drive speakers, but it is good for headphones and power amps. There are other power levels between the two, but the higher is the levels is 'speaker level'. The speaker level signal has a lot of power behind it, enough to driver your speakers. A higher power speaker signal, the better your speakers are going to sound (just b/c of the was the signal will clip or distort if you do not have enough power.)

    USUALLY, what happens, is you have a car radio that has a line level signal running around inside the radio, and before it gets sent to the speakers (a setup w/o amps) it get amplified INSIDE the HU, and sent to the speakers. The amp in the HU is usually lower power, and that's usually why the stock HU's are not so great. The other option for NORMAL setups, is the line level signal in the HU gets mixxed (cd, tape, or radio source selection, then some tone controls and volume) and that LINE LEVEL signal gets sent to the amps. The amp then does it's job of amplifying the LINE LEVEL to SPEAKER LEVEL... Using gain controls, you can ususally get the level's just right, then use the volume control in your computer to adjust the volume (there are other options).

    Now for the trick. If found that my system does not fall under either of the two catagories above. First, the amp does exist, so the amplification is not happening in the HU. The first test i preformed was to plug a line level signal (computer) into the INs of the amp in the trunk. SUCCESS!! Kinda. The sound was coming out of the speakers, but it was very quiet. After some more tests and many visits with the ociliscope, i found that the signal from the HU to the amp (the one i was expecting to be line level) was actaully higher power, higher amplitude than a line level.

    I opened the head unit, and found a small 4 channel, 18w x 4 amp board. This means the signal was amplified some in the HU, then the rest of the way in the amp in the trunk.

    Therefore, depending on your setup, it might be easier to modify your headunit. I found that my headunit had a six wire plug labeled "RF- GND - LF - RR - GND - LR". That was the line level signals going into the amp portion of the board. If i wanted to mod my HU, i would splice my computer signal into that plug. Volume control and everything would then be controlled throught the HU, and the computer audio would be ALWAYS ON, and mixed with the current HU selection. (Listening to a CD from my HU, and directions from my GPS).

    I hope this helps. I would be glad to assist you in your decision and other questions.

    Clay

    ^^^^ Wow, longest post yet....
    System in the works:
    Celeron 850 or PIII 933, SB Live! Value into a stock 4 channel amp, ATI vid, 10.4" sharp LCD w/ allen's controller, Elo SW touchscreen overlay and controller, GPS, TV tuner, FW DVD drive, 4 port serial card, and some other stuff....

    Loads of ideas.

  6. #6
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    wow... that is awesome...

    ok, so assuming I figure out if I have an amp in the head unit, a few more questions.

    how do I get a line level out from the computer? ussually computers have 2 outputs in the form of plugs that go to the speakers... how do you get line level from that.

    than inside the head unit, you could cut the wires, and extend them outside the unit, plug those wires into a switch, and then plug the computer wires also into the switch, and run the output of the switch to the in side of the amp on the wire you origonlly cut. cause I want to keep my radio, but would like to be able to swap my input source, maybe I could even find a switch that would give me the option of mixing them too...

  7. #7
    Maximum Bitrate albysure's Avatar
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    if you really want to do it right check out this:

    http://www.davidnavone.com/adaptor_products.htm

    this guy makes everything. you can even call or email him with your questions. he is a moderator on here:

    http://www.carsound.com/ubb/ultimatebb.php

    he will answer you quick. i use one of his delays to turn on my amps after the computer has booted to avoid the computer turn-on thump.

  8. #8
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    The speaker out on your sound card should be the line level outputs. It should be one stereo jack, that has both Right and Left channels in it. Assuming you do not have jumpers on your soundcard that allow you to switch between line level out and speaker level out, it should be line level.

    As for the HU mod, you can do it however you like. Although, you should go through the process of testing and such (to make sure that you can succesfully get your signal spliced and amped), THEN make cuts.

    IF you can get into your headunit w/o problems, and IF you can find the line level wires somewhere, you then need to try it with your computer signal. Just for safety of your computer, I would try it with another device's Headphone out. Like a small handheld radio or somthing... just in case...

    I did not know about the David Navone guy, but it looks like I could have used him when I was searching and asking about line drivers. Oh well.
    System in the works:
    Celeron 850 or PIII 933, SB Live! Value into a stock 4 channel amp, ATI vid, 10.4" sharp LCD w/ allen's controller, Elo SW touchscreen overlay and controller, GPS, TV tuner, FW DVD drive, 4 port serial card, and some other stuff....

    Loads of ideas.

  9. #9
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    any good way to get lines out of the card? like you have the 2 outs, but they are plugs, how do you get leads for them? buy 2 cables and cut them open?

    or is that what those adaptors do?

    I kinda assume the wires connecting line level to the small amp would have a plug I can just pull off and stick wires into the slots for testing purposes?

    you say not to use the computer cause it could damage it, could it damage the head unit too? if so Im not sure Id be willing to take that risk...

  10. #10
    FLAC MP3DUB's Avatar
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    Originally posted by ares
    any good way to get lines out of the card? like you have the 2 outs, but they are plugs, how do you get leads for them? buy 2 cables and cut them open?

    or is that what those adaptors do?

    I kinda assume the wires connecting line level to the small amp would have a plug I can just pull off and stick wires into the slots for testing purposes?

    you say not to use the computer cause it could damage it, could it damage the head unit too? if so Im not sure Id be willing to take that risk...
    2 Outs? You mean front and rear outs? Depending on what your head unit sends your amp (ie whether it sends four channels or two) it will dictate whether you can use your rear channels on the sound card, otherwise, you just have to worry about the front. And really, unless you're going to be listening to 5.1 Audio DVD's, the rear channels aren't of much use.
    -Nick

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