Question about Dual 2-Channel Bridgeable MOSFET Amplifier (XPA4100) Car Audio Amplifier

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Very confused We hooked up this amp with a sub to an existing head unit that was installed by pep boys. When the install was complete we turned on the car and stereo, the light ignites red for a short time, then goes out. If we remove the ground wire, the led turns red. When we re-attach the ground the light goes out. My friend tested and said the amp is only getting 7 volts. How do I fix this? What causes this to happen?

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Could be you have a bad connection at the battery or at the amp or it could be that you are using a battery source wire to the amp that is way too small. Is the voltage at near 12 volts when the amp is switched off? If it is then either of the two problems I mentioned may need to be addressed. Don't forget to check and see that your ground wire is big enough and short enough and attached to the chassis good enough to carry all the amperage that it must during operation. The size of the fuse on the amp will give you a pretty good indication of which wire size you should be using for both the ground and the hot wires to the amp. A side note: be sure to keep your ground wire very short. On the order of 18 inches or less. A long ground wire can cause some kinds of problems. Good luck.

Posted on Jan 11, 2007


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Subwoofers, on the other hand, require an amp. There are subs that have an integrated amp in the enclosure, otherwise you will need to buy a separate amp. Connecting the amp to your existing system will highly depend on what outputs your head unit (aka stereo) has. If it has pre-amp outputs, those can be run straight to sub amp. If there are not pre-amp outputs, you may have to buy a "high level" adapter that connects to the same head unit outputs as your speakers.

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If there's only a single sub-out RCA cable, you have two options. The amp may have a manual switch that puts it in Mono mode, in which case you only use 1 of the 2 RCA jacks. The other option is to go get an RCA splitter. This will take your single sub-out cable and feed the exact same signal to both left/right of your amp. Either way, you get the same result. If the 1200W amp is for your sub(s) only, you should set the high-pass filter and subsonic filters to help your bass "hit harder" and cleaner.

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Hello cesar199064,

These are the steps you required to install your amp and subs:

1) Purchase an amp wiring kit with 2 or 1/0 gauge power and ground wires.
2) Decide on a location to mount the amp where it will get proper airflow and will not interfere with operation of the vehicle. Closer to the battery is better. Decide on the location and install the sub enclosures.
3) Locate a place on the metal body of the vehicle within about 3" of your amp for the ground. Connect the ground wire to the amp ground terminal and to BARE METAL on the vehicle.
4) Run power wire from battery positive (+) using one of the amp kit ring terminals through a 100A fuseholder to the amp positive terminal. DO NOT install the fuse yet.
5) Run a "remote" wire from the remote turn-on lead (usually blue or blue/white) of your dash mounted head unit to the amp turn-on terminal. Run a set of RCA cables from the preamp or subwoofer outputs on the head unit to the amp inputs.
6) Run speaker wire, preferably at least 12-gauge, from the amp output terminals to your subs.
7) Check all of your wiring. Make sure that no insulation was damaged or peeled off during the running process. Make sure there are no loose strands touching adjacent terminals or bare metal.
8) Use a multimeter set to read "ohms" and test from the negative battery post to the amp ground terminal. You should read "0".
9) Install the fuse.
10) Turn on your head unit and listen to those big Kickers thump.
11) Adjust the amp settings according to your manual.

The best place I've found for in depth information on audio installs is The Install Doctor. You'll find step-by-step procedures, color photos, wiring details, and even the tools required. I recommend that you begin with the "tech docs" link and read through some of the PDF documents.

Hope this helps.

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Cant figure out my car audio problems!!!!!

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The basic would be to wire the sub amp to your batteries with the trigger/remote wire powered by your car stereo/head unit. When your head unit is turned on it will in turn power up the sub amp. Of course the sub woofer need to be wired to the amp. For the signal/audio wiring, normally, the head unit has a stereo RCA female connectors at the rear intended to be connected to external amps through a pair of shielded/audio cable terminated both ends with RCA males. Some units have a special RCA specifically for subs. Most eternal amps also uses RCA for their inputs.

If the existing car audio system has already an external amp and your plan is to add on to this, the audio/signal from the head unit could be split to provide both for the existing and the new sub amp.

If the existing car audio does not have an external amp and their are no RCA connectors at the rear of the head unit, it is still possible to connect an external/add on amp by using an adapter that connects to the speaker wires of the head unit and converting it out to line level (through RCAs) appropriate for the input of the amp.

Hope this be of help/idea. Pls post back how things turned up or should you need additional information. it would also be nice if you can post brand/model of your head unit and intended sub amp.

Good luck and kind regards.

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