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How to ground RCAs with factory HU?

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Old Jun 27, 2012 | 03:01 PM
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How to ground RCAs with factory HU?

I installed an additional amp and 6.5" components last week and have both constant hiss and alternator whine coming through the speakers. I tried an RCA filter but it didn't help much if at all. A little about my system:

Factory Bose car
Female RCA pigtails soldered into pre-amp wires going into the OEM Bose amp.
These RCAs are then plugged in my amps (one for sub, one for components)
Both amps have same grounding point (seatbelt bolt/nut, paint has been sanded away)

I'm thinking now that the factory HU and RCAs are not adequately grounded. What I'm thinking of doing is grounding the RCAs (near Bose amp under parcel shelf) to the HU, and then grounding the HU to something substantial in the center console or firewall.

Thoughts?
 
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Old Jun 27, 2012 | 10:20 PM
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It has nothing to do with the ground. It's a differential-balanced signal and your amp isn't made to handle it.

Read this:
https://g35driver.com/forums/audio-v...-stock-hu.html

If you use a LOC after the amp, it'll be less noisy, but still have the signal ruined by the bose amp's built-in EQ.
 
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Old Jun 28, 2012 | 07:11 AM
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Originally Posted by Wrathernaut
It has nothing to do with the ground. It's a differential-balanced signal and your amp isn't made to handle it.

Read this:
https://g35driver.com/forums/audio-v...-stock-hu.html

If you use a LOC after the amp, it'll be less noisy, but still have the signal ruined by the bose amp's built-in EQ.
Thanks Wrathernaut. I just ordered an AudioControl LCQ1 which should take care of everything including equalization.
 
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Old Jun 28, 2012 | 07:24 AM
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For about the price of an LCQ-1, you could just get a JL amp, which does take differential-balanced signals. http://www.woofersetc.com/p-5583-a43...amplifier.aspx
 
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Old Jun 28, 2012 | 08:58 AM
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Originally Posted by Wrathernaut
For about the price of an LCQ-1, you could just get a JL amp, which does take differential-balanced signals. http://www.woofersetc.com/p-5583-a43...amplifier.aspx
You have a good point... didn't really think about that. I really need an equalizer anyway so I think the LCQ-1 will be good for my application. Hopefully using the speaker-level inputs will get take care of the hiss/whine I'm experiencing.
 
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Old Jun 28, 2012 | 07:43 PM
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It will, to a large extent, as the signal from the bose amp is standard speaker-level output.
 
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Old Jul 10, 2012 | 08:30 AM
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Does anyone no of a decent 5 channel amp that accepts differential-balanced inputs? I want to also run single sub and replace all the bose door speakers.
 
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Old Jul 10, 2012 | 08:35 AM
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Originally Posted by Michael Joneser
Does anyone no of a decent 5 channel amp that accepts differential-balanced inputs? I want to also run single sub and replace all the bose door speakers.
JL XD700/5
http://www.jlaudio.com/xd700-5-car-a...plifiers-98264

A little update on my situation, I returned the LCQ1 and ordered a JL XD 200/2, which is TINY compared to my previous amp. It's about 6" by 8" and sounds great, plus the differential balanced inputs have gotten rid of a lot of noise. I will be ordering an AudioControl EQL soon to take care of equalization.
 
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Old Jul 10, 2012 | 09:32 AM
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Thank you acr, I see that amp goes for about $400. I saw this five channel Alpine amp on Crutchfields website says it accepts speaker level inputs but not sure if that means differential-balanced, http://www.crutchfield.com/p_500MRXV...8#overview-tab

I was also thinking about getting the Alpine MRX-V70 to run four component speakers and using the rca output from that amp for an additional amp(that I have- Kenwood 600w 2 channel), to run a sub.
Would the output rca's from that amp work on a non differential-balanced amp?
 
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Old Jul 10, 2012 | 10:03 AM
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see comments in red
Originally Posted by Michael Joneser
Thank you acr, I see that amp goes for about $400. I saw this five channel Alpine amp on Crutchfields website says it accepts speaker level inputs but not sure if that means differential-balanced, http://www.crutchfield.com/p_500MRXV...8#overview-tab
Unfortunately they aren't differential balanced. Speaker level just means you could tap into the speaker wiring after the Bose amp and run those to the amp (which you don't want to do due to the factory equalization)

You can find the JL amp for less here: http://www.sonicelectronix.com/item_...o-XD700-5.html
EDIT: looks like it is out of stock but I found it on Amazon and other sites for around $425.


I was also thinking about getting the Alpine MRX-V70 to run four component speakers and using the rca output from that amp for an additional amp(that I have- Kenwood 600w 2 channel), to run a sub.
Would the output rca's from that amp work on a non differential-balanced amp?
Crutchfield lists the Alpine amp as not having RCA outputs. But if you did get another amp with RCA outputs, there would be no issue running things the way you described. IMHO differential balanced inputs don't matter as much with sub amps since you won't hear alternator noise.
 
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Old Jul 10, 2012 | 01:48 PM
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Sorry I meant to copy/paste the JL A4300, it has an output I could use for a subwoofer amplifier.

I found the JL XD700/5 here for $403 shipped, http://www.ebay.com/itm/JL-AUDIO-XD7...item4605444b4a

I would really like to install a double din but adding the cost of the JDM ac fascia seems really pricey. Plus I would still want an amp for the components I want to install.
 
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