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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > Remote turn on issue when fitting aftermarket amp to OEM HU



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      01-30-2012, 06:10 AM   #1
bmwak
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Remote turn on issue when fitting aftermarket amp to OEM HU

Hi all,

I recently fitted an aftermarket amp (namely the JL Audio XD400/4) to power my boot sub and a set of components (Focals) that I will soon be fitting to my E92.

As the amp does not have signal sensing, i had to tap into a switched live (cigarette lighter). Now the front speakers and sub only kick in when the ignition is on (i.e. not when the key is just plugged in). I think I can get around this by using a signal sensing amp (which turns on when the amp reads the HU feed coming through). I like my amp so donít want to change it. However, as i am still using the OEM Professional HU, I will need to use a proper line driver (at the moment Iím only using a Directed RCA convertor).

Having had a look at Line Drivers Iíve noticed that two models, namely the Cache COE6 and Audiocontrol LC6i to have signal sensing technology. However, from what I gather they still require a switched live signal. My question is will adding one of these into the system cure the issue of having the amped speakers only kicking with the ignition on. The Directed RCA convertor works fine with no audible interference or anything Ė so I donít want to waste money on a line driver if it wonít help me fix the issue iím having.

Can anyone help on this?
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      01-30-2012, 06:23 PM   #2
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See the new table of contents thread 2d post
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      01-30-2012, 07:04 PM   #3
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Signal sense widgets work fine in that car. PAC TR4. Solves that problem cheaply.

You don't need a line output converter. The 400/4 can take that speaker level input.

BUT... the head unit output is not linear, so you are amplifying a very nonlinear signal. If the signal coming out of your head unit were linear, this graph of the electrical output would be flat:



So you're gonna want to correct that or it doesn't matter what else you do. The Jl CleanSweep will correct it on the front channels AND do signal sensing...
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      01-31-2012, 08:32 AM   #4
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Quote:
Originally Posted by VP Electricity View Post
Signal sense widgets work fine in that car. PAC TR4. Solves that problem cheaply.

You don't need a line output converter. The 400/4 can take that speaker level input.

BUT... the head unit output is not linear, so you are amplifying a very nonlinear signal. If the signal coming out of your head unit were linear, this graph of the electrical output would be flat:



So you're gonna want to correct that or it doesn't matter what else you do. The Jl CleanSweep will correct it on the front channels AND do signal sensing...
Thanks for your reply - this is very helpful info!

I have been looking at buying a DSP unit and was looking at the MS-8 but thinking of adding it a bit later as it is a bit over my budget at the moment.

The JL Audio CL441DSP Cleansweep unit seems to fit the bill, both budget-wise and provides the signal sensing function to correct the issue. Is there any major advantage on going for the JBL MS-8 (apart from the fancy screen) over the JL Audio CL441DSP?
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