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12v dc to 7v dc for amp on

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=109876
Printed Date: May 20, 2024 at 2:35 PM


Topic: 12v dc to 7v dc for amp on

Posted By: frankgant
Subject: 12v dc to 7v dc for amp on
Date Posted: December 19, 2008 at 12:24 PM

Hey guys.  I've got an Ford Expy that has a built in sub and amp.  I put a new head unit in and the voltage coming out of the new head unit to kick on an external amp is 12v.  The old factory unit only used 7v to turn on the factory amp.  Does anyone have a quick and easy solution for dropping the voltage to 7v?  I thought about using a resistor but have no idea how to figure which one I would need.  I know diodes work too but again I don't know how to figure which one I would need.  So any help you could provide would be greatly appreciated.  Thanks...

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- Frank



Replies:

Posted By: kassdog
Date Posted: December 19, 2008 at 1:49 PM
It should still turn on but you might here a pop. I believe I always put in a 1500 ohm resister in the fords.




Posted By: frankgant
Date Posted: December 19, 2008 at 2:28 PM
I thought it would come on too.  I hear the pop but I never get any bass from it.  It worked before I put in this head unit.  I couldn't get a connector that would fit so I took one apart that I had to use the rca connectors from.  The wiring is pretty straight forward but still I get no bass.  I've made sure the bass outs are active on the head unit too.  If I can get bass then I'll go out and find the resister needed to get rid of the pop.  Any ideas why I still get no base hooking it up to the 12v even though I hear the pop?  There are only 3 wires to connect to the RCA's from the truck so I assumed they shared the braided wire???

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- Frank




Posted By: frankgant
Date Posted: December 19, 2008 at 5:25 PM

Okay, so here is what I've found.  There were two wires from the original harness that were for inputs to the amp, at leats that is what I thought.  There also was the braided wire which I assumed the other two shared.  Then of course the green wire which is to turn the amp on.  I found that connecting the first two wires to two diff. rca's while having the braded wire attached for both doesn't work. The amp will come on but no sound.  If I remove one of the original wires I now have bass.  Doesn't matter which one is connected or not.  So good news there.  Now however that I have bass I also have amp noise.  I've tried different configurations of the wiring to see if it would go away but have had no luck.  I have a hard time with this noise because I'm using original wiring and it's the factory amp.  So if there is a problem with grounding, like a loop, it should have always been there.  I've added no additional grounding or changed anything other than connecting my harness for my reciever.

Any ideas before I just go out a buy a new amp that takes 12v and that I can ground and run RCA's to and just be done with the whole thing?  I hate to spend more money when I would just be happy with factory.  Thanks again for any help.



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- Frank




Posted By: KarTuneMan
Date Posted: December 20, 2008 at 3:37 AM
Find a Peripheral PTR7.....

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