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Thread: Any car audio geniuses or EEs in here? Head units, amplifiers, CD changers, oh my!

  1. #1
    Join Date
    Oct 2019

    Any car audio geniuses or EEs in here? Head units, amplifiers, CD changers, oh my!

    So I got in a little over my head here thinking I could easily integrate a car audio system and connect my phone (hardwire) to a factory head unit. The cassette player is very charming and I don't want to replace it with a different head unit, and I'm sure many of you understand that. I have a lightly spec'd system with new door speakers and a powered sub. My car doesn't have the factory CD Changer or subwoofer. I've seen the PIE FRD03-AUX unit (which converts an RCA signal to the 16 pin CD changer input), and pending great luck that I found a place online with one in stock, that'll work great (albiet with what looks like a need to attenuate it into the head unit). But I am highly skeptical that they have some old drop shipping spreadsheet they're using and after I order this thing in a couple days they're going to tell me it's out of stock.

    So if I can't get a hold of that thing, I saw on a BMW forum someone had another solution that seemed promising.

    1. iPhone > JL Audio bluetooth receiver to RCA out (this is spec'd for marine audio, which I suspect is properly attenuated\level matched for aftermarket amplifier levels)
    2. RCA out (unknown signal level currently) SPLICED into CD Changer audio wires (currently unknown level)
    3. Not sure how I need to terminate the CD changer audio wires, or if at all.

    From what I understand, inserting a CD into the head unit disables all input from the CD Changer. And if I take the CD out, but select CD and the changer signals to the head unit that it has a CD (assumed), then it will play from the changer (I know this is the correct behavior, but don't know how the head determines it completely).

    This is ideal.

    There's only a couple issues I have to unwind.

    1. The PIE FRD03-AUX unit, and actually several across different car brands seem to have some complaints over "distortion." This seems to be a level mismatch between the RCA output and 16 pin input on the back of the head, shoddy engineering on PIE's part.
    2. I do not know the expected output level of the CD Changer into the 16 pin connector into the head unit (though I can level match this by comparing it to CD output from the head)
    3. SOLVED - The head unit does not output levels that the aftermarket amplifier will expect, so JL audio makes a very nice line attenuator for this purpose.

    So if I can get anyone in here that either knows, or is willing to measure

    A. Audio output level from the CD Changer (that is the two audio wires in the 16 pin connector out of the CD changer into the back of the head unit)
    B. What signals the changer is sending to the head unit that may be of concern with this idea

    Any help is very much appreciated, I am at the mercy of this shoddily designed part right now and don't want to hack the car up and take away its charm.
    Last edited by Nickerz; 01-25-2024 at 03:34 PM.

  2. #2
    Join Date
    Oct 2019
    Alternatively, it looks like Soundgate SDSFord might be a replacement for the PIE FRD03-AUX, just without the cable to connect to the changer wiring. So instead I would just buy the SDSFord module & a CD changer wiring harness.

    Does anyone know the CD changer wiring harness part number? Or places that will build to spec\pinouts?

    If I have to get a CD changer, is there anything fancy to power it? Is there two harnesses then? One to power the unit and another to the head unit?

  3. #3
    Join Date
    Oct 2019
    Okay I think I got this figured out.

    SOURCE 1 : Stock head unit > JL attenuator (set to match JL Marine output levels)
    SOURCE 2 : JL Marine Bluetooth Unit (assumed to be outputing correct levels for aftermarket amp)

    both of these go into an RCA switch, then into the aftermarket amp. Then I don't have to futz with the levels in the PIE\other adapter units. Now only issue is finding an automatic RCA switch I can trust. Alternatively, if that doesn't work out, I suppose I can just keep the bluetooth connection wired until I get around to getting the factory head unit working again. I am worried about *****y grounding with these automatic RCA switchers.

  4. #4
    Join Date
    Feb 2007
    Winston Salem, NC
    There are some wiring gurus on here...Here's to hoping they can help out! Most of us have chucked the factory unit when we went with Carplay/Android has just come sooo far over the years! We hope you get it friend, we are for you!
    2003 300A
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  5. #5
    Join Date
    Oct 2004
    Cape Cod, MA
    A fix for old tech is never 100% in terms of performance. Change the old head for new tech.
    2004 marauder black purchased new. Sold 9/16 at 297,000 miles. Still ran strong didn't burn a drop of oil.
    2003 marauder black 28,000 miles all stock. Garage Queen.
    2004 marauder red daily driver.

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