2007-18 Jeep Wrangler JK JKU Alpine System Amp Interface – AmpPRO 4 AP4-CH21


2007-18 Jeep Wrangler JK JKU Alpine System Amp Interface – AmpPRO 4 AP4-CH21

If you have talked to me on the phone before about your sound system in your Ram, then I have talked to you about this part. This may also be a bit repetitive, but I want people to know how much of a God send this piece is. This interface came out to market around February 2017 and every one that we have used works. It just works. First time, every time. So if you plan on upgrading everything in your sound system, or even just adding a subwoofer, then this is the way for you to do it.

In 2007, Jeep Wranglers came with a new Premium Sound System option, Alpine. While they are a definite improvement from the base audio package, they are still lacking when compared to a true premium, aftermarket sound system. But, it comes with it’s own complications.

This interface takes the crazy signal out of the factory radio, and uses the data coming out of the radio to control the amp, to give us usable RCA outputs for Front, Rear and Subwoofer. It even has a subwoofer knob and creates a remote turn-on signal for you. Wiring wise, it is a plug-n-play T-harness. You pull the radio, unplug the factory harness, plug this in between the two, and put it all back together. Easier than installing an aftermarket radio.

This is the geeky part about how the system works if you are interested.

The way these systems are designed is way different from your base audio systems. Your regular radio has 8 speaker wires, 4 pairs; Front Left, Front Right, Rear Left, Rear Right. These wires vary in volume as you turn the volume knob, adjust fade/balance, EQ, everything. Normal type of radio. With the Alpine System, there are only 4 wire, Left and Right. They are also a fixed volume, meaning if you hooked a speaker up to them they would just play loud, no matter what you did to the volume knob. That fixed level audio signal then goes to the amplifier and the amp is told to do volume, fade/balance, EQ, everything, through a data signal from your radio.

Then, the amp does it’s thing. Instead of just power, the amplifier heavily processes the signals going to the speakers. It limits the audio range of each speaker, through crossovers, so the tweeters only play the highs, the woofers play the mids, and the sub just plays the deep bass. There are no full range signals going to or coming out of the amplifier that you can tap into for an amplifier.

So, in the past, the best way to do this was to use a signal summing device, we like the ones from AudioControl, ARC Audio and DD Audio, but there are many other good ones on the market. The signal summing combines the signals and creates a full range signal that you can send an amp. But, if the wires aren’t correct or on pair is out of phase, then it can create a whole new mess for you.

Then, the next problem is that once you cut the speaker wires from the factory amp or disconnect a speaker, the amp stops putting out audio. So if you have it all wires up but the factory amplifier does not see a load, or thinks that it sees a speaker, it will turn off that channel. Well now you have to install load resistors to keep the audio signal working, and there is no real way to install load resistors and have them look good, or factory.

This is how the system works and what is in the way. By using the PAC AP4-CH21 harness, you eliminate the need for signal summing, load resistors, all sorts of issues. This is a plug-n-play kit that goes behind the radio and does all of the hard work for you.

PAC Audio AP4-CH21

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Additional information

Weight 1 lbs
Dimensions 12 × 12 × 4 in