# voltage drop at amplifier?



## carter1010 (Sep 20, 2009)

I have a Battery, a alternator upgraded to around 120 amp output and the voltage at my amp is 11.1 or so with the car running according the readout on a SX900.2. The wire running to the distribution block is 1/0 gauge as is the ground. distribution block takes the 1/0 and splits to 4/0 for both power and ground. The amps currently installed are a ZX850.4 and a SX900.2. The sx display says 11.1 volts or so with a little fluctuation and shuts off if I crank the volume. I have adjusted the gain all the way to the lowest settings and it still acts as though it is not getting enough current. The ZX stays on just fine no matter what. Any ideas? 

How does one go about getting 14 volts at the amplifier input?


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## IceWaLL (May 30, 2005)

what is the voltage at the battery? 

have you checked the ground?


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## kyheng (Jan 31, 2007)

X2 on check the ground..... Best still another run back to battery dirrect


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

kyheng said:


> X2 on check the ground..... *Best still another run back to battery dirrect*



Check the ground, but running back to the battery for ground is not a great idea.. 

The chassis of the car is a FAR better ground than 4 or 1/0awg



I would be checking voltage at the battery too.. or right off the alt.. could be a crap alt...


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## kyheng (Jan 31, 2007)

Emm... You have some point here, but what if the original ground cable also a crap?


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

kyheng said:


> Emm... You have some point here, but what if the original ground cable also a crap?


would be FAR easier to replace 1-2' of cable than 10'....


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## carter1010 (Sep 20, 2009)

Ground is 2 ft long at and grounded to the frame. Area where ground is attached has been ground smooth. Last I checked the voltage at the battery was over 12 volts and when the car was running it was 14 volts. I will check it again tomorrow just to be sure. All connections are relatively new and tight.


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## kyheng (Jan 31, 2007)

Aaron'z 2.5RS/WRX said:


> would be FAR easier to replace 1-2' of cable than 10'....


If I have the proper tools for this, i'll go for it... But I don't want to disturb the original.....


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## jalba (Dec 20, 2010)

An "upgraded" 120A alt is most likely an alt that used to do ~70 amps at full throttle, maybe 45 at idle. Now it probably still does 50 at idle and 120A (if you're lucky) at 4k rpm. I'm assuming you didn't actually test your alt with an amp clamp after it got upgraded. Buy a clamp that can handle 300A and test your alt. I can almost guarantee that it's too weak. Even if it put out 120A at idle, it would be too weak. My stock alt does 130A, so something's not right if an "upgraded" alt is only 120A. You need a second alt, or an actual HO alt. But before you spend any more money on alts, buy an amp clamp DMM and read this page at the link below. It's a lot of info, but well worth your time.

Learn about choosing and retrofitting high output alternators


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

kyheng said:


> If I have the proper tools for this, i'll go for it... But I don't want to disturb the original.....


Add to, don't replace, unless you go even bigger...


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## cubdenno (Nov 10, 2007)

I agree that something is amiss here but I kindly disagree that adding a dedicated ground run is useless or inferior to chassis ground. I added a dedicated ground run to my Solara and 2 runs to my son's Buick (he had 3kw just on the subs) and saw in my case about a .5 volt voltage increase over chassis ground alone. Remember that in todays use of welds on the frame, not metallic bushings, and whatever else they use to decouple, the chassis is not such a great ground. And check your resistance with a DMM and you will see a huge drop between the 1/0 and the metal of the car. My voltage drop decreased, my interior and rear lights got visibly brighter as well.

Also look at what SPL guys do. They also add dedicated runs of cable for the ground. It is not a useless endeavor.


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## kyheng (Jan 31, 2007)

Aaron'z 2.5RS/WRX said:


> Add to, don't replace, unless you go even bigger...


Case by case I would say, on this. If you got a good frame that having lesser resistance, adding ground on top of original will be good. 
But a sh*t chasis you add another run also will be the same, useless.....


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