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Old 04-07-2013, 12:43 AM
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Remove factory amp - retain bass/treble control

So I've been working on replacing the amp and speakers in my '13 JK. It has the Alpine factory system with the amplifier under the dash.

I read that to add another amplifier to this, a special adapter that reads the CAN bus signals from the head unit is required so that fade/balance and volume work correctly.

However, I also read that if you remove the factory amp, the standard adapter that just takes the speaker outputs and converts them to line level will work. I ended up buying both types of adapters because I wasn't sure what to expect.

I started by disconnecting my factory amplifier and using the standard head unit line level converter. Initially this worked like a charm. I had fade, balance, treble, bass, and mid control from the head unit through my new amps.

However, after starting the vehicle for the first time, the factory Radio reverted to thinking the factory amp was there and I had constant volume, with no fade, balance, or tone controls.

I think this happened because I had left the battery disconnected while I did the install, and then after the first start of the vehicle, the Jeep's engine computer communicated with the factory radio over the CAN bus and told it "hey, you have a factory Alpine system".

Anyway, I ended up putting in the "special" CAN bus adapter and now I have fade, balance, and variable volume, but no tone controls.

Also, the fade and balance are a little wonky. I have to put it 1 step to the left side to get it to correctly balance the speakers at low volumes. I'd rather just use the standard adapter, and get tone controls back.

Has anyone had any success in using a standard adapter with the Alpine or Infinity systems after removing the factory amplifier?

Do I have to get the dealer to program the computer or radio to tell it "hey, you don't have the factory amplifier so revert to normal speaker control"?

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Old 04-07-2013, 09:04 AM   #2
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How did you tie in the line level converter(s)? With those, you need a standard amplified signal - so you must leave the factory amp in place and plugged in. Then, tie your line level converter to the factory amp's outputs for the front and rear speakers. If you are doing an aftermarket sub and amp too, than you will also need a converter for the sub signals. There is no way to interface into the audio signal between the radio and amp - it's all a summed data-based audio signal. If you want to keep the stock stereo, and add amps than the factory amp needs to stay. If you don't mind replacing your headunit too, than the factory amp may be removed, and you will also get better overall sound quality than you would with the stock headunit.

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Old 04-07-2013, 12:18 PM
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PAC, Metra, and others make interfaces that work with the data bus (CAN bus). I bought one of those, as well as one that was made for the non-Alpine/Infinity JKs just to try it. I was under the impression that if I disconnected the factory amplifier, the factory radio/headunit would revert to a normal amplified 4 channel stereo with built in fade, balance, and tone controls.

It actually worked that way, until I started the vehicle up. At that point, I'm guessing that the Jeep engine computer communicated with the radio and reprogrammed it to work as if it had the factory amplifier still installed.

After that, I switched out the standard line level converter for the one that supports the data bus and constant level speaker outputs. This was a PAC C2A-CHY23 adapter if you are interested. The problem is with this unit that there is a bit of noise and that there are no bass/treble controls.

I'm wondering if anyone has had any experience getting their JK headunit or engine computer that had an Alpine or Infinity system reprogrammed so that it works like a normal radio. (The way mine worked until I started the car after having disconnected the battery for about an hour.)
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