Bypassing Boston Acoutstic amp on Jeep REC w/ Nav

General discussion about interfacing with the CAN bus
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scott
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Bypassing Boston Acoutstic amp on Jeep REC w/ Nav

Post by scott »

The upgrade stereo for 2006 Jeep Grand Cherokee is a Boston Acoustics' system that has a rear amp. The amp's inputs are the left and right rear outputs from the Alpine-produced REC radio, two CAN B wires, power, and ground. The output is simply 6 pairs of speaker wires. Dash, front door, rear door...

I have changed out the speakers to better ones and am trying to bypass the factory amp altogether. I intend to use the radio's rear high-level outputs as inputs for an aftermarket amp.

So far I have simply bypassed the factory amp and connected the speaker level wires from the radio to the new front speakers as a test.

Works great, but now nav and bluetooth don't produce sound over the speakers. What gives? How did that signal get to the speakers in the first place, if not through the only wires that went into the amp.

I know nothing about CAN bus, but I believe the radio is used in other cars without an amp and that in that case the nav and bluetooth phone sound comes through the front left speaker.
Maybe i can just use the front left out?

Thanks in advance for any help you can give.

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linuxkidd
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Post by linuxkidd »

Ok.. here's what's going on...

When the Factory AMP is connected and sensed on the CAN bus, the Radio ( REC ) puts out a LINE level speaker voltage that the factory AMP uses as it's input. This signal does NOT change with volume level, nor with EQ settings. All these changes are handled by the factory AMP with data received over the CAN bus from the REC unit.

When you disconnect the Factory AMP and it is No longer sensed on the CAN bus, the Radio ( REC ) puts out a HIGH level ( speaker level ) output that is Volume controlled and varies with EQ settings. HOWEVER: You loose bluetooth and nav audio.

The only way to have everything work is to apply the outputs of the Factory AMP into some sort of summation device ( Like the AudioControl LC6 ) to sum all the outputs together and produce a single line level output. You will loose Fade control, and the NAV & Bluetooth voice will go to both front and rear speakers... but, it'll all work, and sound fairly good.

The problem with this "recommended" setup is that the factory AMP has a pre-set EQ inside to compensate for the crappy speakers that DCX puts in the vehicles. So, even with this summation device, You still inherit the EQ settings and thus will have to tweak the audio to make it sound the best that you can. If your a TRUE audiophile and want nothing but 100% pure signal, the only thing you can do is replace the entire system, New head, amps, and speakers.

The Factory AMP splits the front signal into a Mid/High frequency to the dash speakers and bass/sub-bass to the front doors. The rear speakers seem to have full range audio, so you may consider using the summation on the front channels, and then a regular line level converter on the rear output to have seperate front and rear outputs such that the fade will continue to work.... But I'm not 100% certain the rears are full range.

If you have any other questions, please feel free to ask!
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scott
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Post by scott »

Wow! Thanks, you are the man. You have no idea how many people I have tried to get to help on this.

Would it be possible to connect the old wiring harness, complete with can bus wires, 12v wires and ground, but minus the rear speaker wires?

Then, I could use the speaker wires' low level signals, unequalized, with a afterfactory amp and ignore the output from the Boston amp. This probably wouldn't work, but it is a question.

thanks again

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Post by linuxkidd »

When the amp is connected, the signal coming from the REC will be Line level, and a nice clean signal. HOWEVER: It does not vary with the volume control. So, you wouldn't be able to adjust the volume with the REC ( or steering wheel controls ).

You would need to have a remote volume control from some sort of gear... Maybe a DSP, crossover, or the amps themselves.


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egocogitovolo
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Post by egocogitovolo »

Ok first post but I have been lurking for quite a while... I am working on a carputer in a 06 Jeep commander. My first step is to get info from the CAN interface as I don't want to have to buy and try to rig some of the PAC products to do steering wheel controls and AMP control and Sirius control. I am working on not replacing my factory amp and Sirius setup. but removing the factory stereo and replacing it with a Xtronic HQCT-i usb radio / receiver. I am assuming I can use the line level output to connect to the factory amp with the factory wires that the current radio is using. But at that point it gets complicated, as stereo control (volume, steering wheel, Sirius) would have to be done with CAN requests? I have plenty of time on my hands for this project as I assume it is going to take a while to map all of the data.

I guess I am posting as a sanity check, Linuxkidd does this sound feasible as a goal?

Also has anyone used the: http://www.qprotos.com/quickcan.htm Just wondering as it has its own software setup that may make things easier, as long as it works?

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Post by linuxkidd »

Sound VERY feasible. Agreed though.. It will take a LOT of time.

It may be easiest to pick up some of the PAC adapters and fire them up on a test bench to capture the data they're pumping out. It would give you the data needed to turn on the AMP... However, there's some other comms that's required for the vehicle to think the radio is still there. I have the Pac C2R-CHY, but still get logged entries on the CAN bus that the Radio is not on the bus.

I wish you the best of luck, and I'll answer any questions you have along the way.. Feel free to keep this thread ( or start another thread... CAN Carputer, or similar ) to keep us up to date on your findings..

Also, if you'd like to get a copy of all the capture data in a Mysql Dump format along with the can_log analyzer to setup on a local system for quicker browsing. lemme know.

Thanks!
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egocogitovolo
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Post by egocogitovolo »

Thanks Linuxkidd once I get all my parts I will start another thread with my work log. I will PM you with my info for the MySql dump.

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codekey
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Re: Bypassing Boston Acoutstic amp on Jeep REC w/ Nav

Post by codekey »

scott wrote:The upgrade stereo for 2006 Jeep Grand Cherokee is a Boston Acoustics' system that has a rear amp. The amp's inputs are the left and right rear outputs from the Alpine-produced REC radio, two CAN B wires, power, and ground. The output is simply 6 pairs of speaker wires. Dash, front door, rear door...

I have changed out the speakers to better ones and am trying to bypass the factory amp altogether. I intend to use the radio's rear high-level outputs as inputs for an aftermarket amp.

So far I have simply bypassed the factory amp and connected the speaker level wires from the radio to the new front speakers as a test.

Works great, but now nav and bluetooth don't produce sound over the speakers. What gives? How did that signal get to the speakers in the first place, if not through the only wires that went into the amp.

I know nothing about CAN bus, but I believe the radio is used in other cars without an amp and that in that case the nav and bluetooth phone sound comes through the front left speaker.
Maybe i can just use the front left out?

Thanks in advance for any help you can give.
If you take the factory amp off the Data bus then the Bluetooth audio will come out of the front speaker wires. However the vehicle harness does not have wires on the front outputs, only the rear. If you can get some wires placed into the plug for the front outputs, then you can get both front and rear outputs that vary with volume adjustments.

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Re: two question

Post by CHACHY »

Hello Linuxkidd.

I´m Antonio form Spain.

I need you help.

I have 2 question

I have a JEEP Grand Cherokee WH 2005 3.0 CDR Limited (European version) with original navigation system REC (European version).
Now I changed the factory radio to Adroid radio with compatible Jeep audio connector and have a canbus decoder for Jeep/chysler.
The amplifier work with this radio but no work Fader, only balance

1) Can you confirm me that the input pins for Boston amplifier audio are in the Amplifier connector C2, pins numbers 7(+) ,8 (+), 18 (-), 19(-)
Why ther is only one input, only REAR? Where the amplifier take "fromt audio", because dont have pins with fromt imput?

2) The car system cant change the lenguage, always in english because the canbus from android radio only can work in english and you cant change
the car computer laguage , with factory REC radio I can change the language to spanish, It is any solution to change the language?

The android radio work fine with steering wheel button.


THANK A LOT AND SORY FOR MY ENGLISH

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Re: Bypassing Boston Acoutstic amp on Jeep REC w/ Nav

Post by linuxkidd »

Hi CHACHY,
The BA Amplifier has only 1 pair of stereo inputs, usually driven by the 'rear' output of the new headunit. The fade ( front to rear ) is controlled over the CAN-bus by the factory radio. So, with an aftermarket unit, you'll have no fade control.

I'm not familiar with any ability to correct the language.

If you're good with code, you can likely create your own Arduino (or similar) based fade / language correction. Someone else on the forum may have more details to help with this.

Welcome to the forum, and best of luck. Your English is WAY better than my Spanish. :D

Hope this helps,
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CHACHY
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Re: Bypassing Boston Acoutstic amp on Jeep REC w/ Nav

Post by CHACHY »

thaks a lot

CHACHY
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CAN B BUS + and CAN B BUS -

Post by CHACHY »

Hello again.
Some china android radio don´t come with specific can bus, but come with similar wire like, (Can_TX Can_RX) or KEY1,KEY2 and KEY-GND.
How do you think that can work fine with my Jeep Grand Cherokee.
the origina imput in JEEP Can B Bus (+) wire 4 and CAN B Bus (-) wire 6, it compatible o connect Can_TX and grounD?

Can Bus (-) is the same like Ground? or it is different negative pole ?

the audio input of boston amplifier can work whith RCA OUT and not use the left an right rear audio out hight level from radio? that is because I think that hight level audio out form may china radio when are working abuto 10 minutes the left channel the audio level go down, and I want to try to connet the RCA to the wire of input of connector thant go to the amplifier

Thank a lot

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