I have just purchased a 4 channel amp (Alpine MRP-F450) to run my interior speakers.
I currently have 4 ga. ran in my car from battery to trunk, which is way more than my current 400watt monoblock requires on its own. I think that the total fuse rating between the two amps is somewhere between 90 and 110 amps, I can't remember off of the top of my head.
My new alpine uses 2 x 30A fuses on its own but it will only be running @ 4 ohm on all channels, none of them bridged. Because of this I believe my 4 ga from battery to trunk is still ok to use.
My question lies with the wiring once in the trunk. I obviously have to go and pick up a distribution block and based on the owner's manuals for both amps each amp only requires 8 ga. Is it ok to take the run of 4 ga. back to the trunk, split it to 2 8 ga. power leads, and then ground each amp with 4 ga. grounds?
The reason why I ask is that I have enough scrap 4 and 8 ga. around to do the install but only in this way. Would I be better off just going out and getting some more 8 ga. so that power and ground on each amp are the same size?
Also, must the 2 amps be grounded at the same point? I think the answer is yes, but it would be a lot easier if it were no.
Thanks
as long as your ground is equal to or larger then your power wire size you will be fine
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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place
That's what I figured, that's why I said I'd use the 4 ga. as grounds. I'm hoping this might help too because my grounds might be a bit longer than 3 ft. especially if they must ground at the same point.
Speaking of which is this truly necessary? By my reading I've heard that ground loops may develope when multiple amps have the same power source but different grounds. Is this myth or fact?
I was hoping to install my 2 amps on the 2 opposite sides of the trunk.
I'd ground each amp about an inch apart...not in the exact same point...each amp would be grounding at different rates...may affect the other.
Hmm interesting. Never thought of that before but it makes sense. I'm going to ground near where the current ground is for the monoblock. Behind my backseat there's a metal square tube brace, not painted and bolted dirctly to the body. It'd be super easy to create 2 solid grounds on there.
You can also use a ground distribution block, might make it a little easier and cleaner.
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The reason for using different locations instead of stacking the rings on one bolt is for the best contact-to-sheet metal for each ground wire. The second and third stacked wires might not get as good a contact as the first one, or the contact could weaken over time due to oxidation or whatever affects metal contacts. And the reason the wires are grounded very close to each other is to eliminate possibilities of ground loop if they are spread far apart.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
I have had it happen before once, where one amp was effected by having 3 amps grounded to the same point. I cleaned up the connections and all was good again, but since then everything gets grounded to the batterys ( The great ease of having batt's in the trunk) and the batts are all grounded to 3 diffrent spots.
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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place