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    Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    I've searched high and low, this forum, that forum and all in between and have YET to find an actual definitive answer, so let's see if we can just get the correct answer out there and be done with it.

    My $400+ dollar Headunit (New in 2011) has a black RCA line out that says "Subwoofer" on it. Obviously, RCA's come in pairs. My amps input has 2 RCA's. This is the "dilemma" or the question:

    What is the 100% "book" way to make this connection? Do you put a Y splitter RCA into the headunit subwoofer out and run it as normal, or do you just connect ONE of the RCA's to both the headunit and the amp because the amp "knows it's mono anyway and only needs one"<~(That's not what I am saying, it's what I've read)

    The general consensus basically leaves 2 answers that make sense, but nothing definitive, and 1 answer that's just asinine.

    1. Plug 1 RCA into the headunit and 1 into the amp. The amp handles the signal internally, and there is no need for a splitter or any other alterations.

    2. Use a Y-splitter. The problem with this is you will split the signal and only get half the voltage which you can make up with the gain setting.

    3. Buy a better headunit loser. One that has 2 outputs.

    All 3 of these are what I have come across on multiple forums. The 3rd one is retarded, because my headunit was $400 and does not need to be upgraded to accomplish this connection.

    Maybe someone's search/googleFU is better than mine, and I apologize in advance if this has been discussed in depth as I have not been able to find it.







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    Re: Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    buy a y-splitter or a nice DD amp, some of those only have a single rca input for the sub. (some other high-end amp do also)




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    Re: Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    Use a Y-Splitter. This is the *only* way to be 100% sure the mono HU output will work with *any* amp without knowing the make/model of amp you are using and how the output is wired (bridged or normal).

    Your assertion about half voltage is WRONG. The HU RCA output is low impedance and the amp inputs are high impedance. (Very close to) the same voltage will be present at both amp inputs as would have been present at one input.

    Most manufacturers will tell you in the manual the best way to connect a mono sub signal for that particular amp. It varies. But if in doubt, just use a Y-splitter.

    I won't profess to be an absolute expert, but I have been an electronic design engineer for 25 years and a car audio enthusiast for longer than that. I am very open to hear other opinions on this one.




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    Re: Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    Quote Originally Posted by Jepalan View Post
    Use a Y-Splitter. This is the *only* way to be 100% sure the mono HU output will work with *any* amp without knowing the make/model of amp you are using and how the output is wired (bridged or normal).

    Your assertion about half voltage is WRONG. The HU RCA output is low impedance and the amp inputs are high impedance. (Very close to) the same voltage will be present at both amp inputs as would have been present at one input.

    Most manufacturers will tell you in the manual the best way to connect a mono sub signal for that particular amp. It varies. But if in doubt, just use a Y-splitter.

    I won't profess to be an absolute expert, but I have been an electronic design engineer for 25 years and a car audio enthusiast for longer than that. I am very open to hear other opinions on this one.
    Nice. Again, not *MY* assertion, the internets. Even on this forum, people say splitting it will cut your voltage and that you shouldn't. My amp is a Rockford Fosgate T1000-1BDCP and I have a Sony XAV-70BT 7 inch in dash.




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    Re: Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    if you don't split it, your only sending half the signal to either the left side or right side, by splitting it you atleast have the full signal coming out of your headunit going into your inputs on your amp.




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    Re: Headunit: 1 Subwoofer out RCA=Amp: 2 Subwoofer in RCA

    I looked at the amp's manual. It shows stereo inputs and says nothing about mono inputs. It looks like a basic 2-channel amp that is internally bridged to make it "monoblock". In order for a bridged output to work properly, there has to be a signal present on both L and R inputs. I highly recommend you use a Y-Splitter into this amp.

    Y-SPLITTING DOES NOT CUT THE VOLTAGE IN HALF - read on, the example is typical:

    Use this calculator to figure it out.
    http://www.sengpielaudio.com/calcula...agedivider.htm
    ------------
    Vin = Enter HU output voltage
    Z1 = Enter HU output impedance
    Z2 = Enter Amplifier input impedance
    Zload = Enter Amplifier input impedance.
    ------------
    Example.
    Vin = 5 volts
    Z1 = 200 ohms
    Z2 = 20,000 ohms
    Zload = Don't enter anything, default is 1 megaohm.
    -------------
    The HU outputs 5V, but with amplifier connected, the loading effect of the amp causes
    the voltage to be 4.95 volts.

    If you connect another amp, lets say it also has 20,000 ohms input impedance,
    the calculator says;
    -------------
    Vout = 4.90 volts

    With one amp, 4.95v
    With two amps, 4.90v
    ------------
    *What if*
    Vin = 5 volts
    Z1 = 2000 ohms
    Z2 = 10,000 ohms
    Zload = 10,000 ohms

    With two amps, 4.54v
    ------------




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