It should come with fuses in it ready to go...? Amps vary in what fuses they use. read the manual it should tell you

 

Actually, I'm not referring to the fuse on the amp. I'm referring to the in line fuse that connects to the batter.

 

Oh , okay. Then you only need one but it should be added no further than a couple of inches from the positive side of the battery. Im running a 400watt amp and my fuse is a huge 100amp fuse but i think 80 or so is fine. If you guy an amp kit it should come with the fuse and it holder. I would recommend running 4awg power cable. You can get a good kit from wal-mart for cheap.

 

I already got the kit, but I think I got the wrong one after reading this http://www.crutchfield.com/installguide ... gauge.html

I should have gotten a 10 gauge since my amp max out is 400 watts, which is a 57 something amperes.

Oh well, at least the amp works. I just don't know if it will effect the system in anyway by not adhering to these specs.

 

Trust me you dont want 10awg wire to get power to your 400watt amp. You want 4 awg. Keep in mind electricity flows like water . The bigger the pipes the easier it will flow. If you ask any car audio pro they will tell you the same. You can probably use 8awg and be fine but if your running all 400 watts of that amp 4 awg would be better with a 4 awg ground.

 

You don't want to go too high on the amperage of the fuse because then it may not blow soon enough, and potential damage to your equipment and/or vehicle could occur.

Use this equation: P=I*E, where P=power (400W), I=current (unknown), and E=voltage (12V). Solve for current. Take P/E (400W/12V) = I = 33.3A. You'll want a 40A fuse optimally in that configuration, possibly a 50A if your amp overdrives. Most likely, your amp has 40A worth of fuses on it already. The more overrated the amperage on a fuse, the longer it will take to blow. When a short occurs, the current doesn't instantaneously reach infinity. Integrated circuits require nanoseconds to switch between one another. If that surge of current reaches through and blasts a gate that cannot handle it, or any electrical component, then it may blow that IC or component. Nanoseconds of difference is what you'd see in fuse reaction times when one blows. Nanoseconds is all it takes to potentially do damage, whereas none may have been done before.

Now, using some equations I know, if you're using a copper wire, 10AWG will drop ~16% of its voltage at the end of a 20' length, based on 40A maximum current. 8AWG will drop ~10%, which is a grade of wire commonly used up to ~600W (and it will work). 4AWG, however, will only drop ~4% of all voltage, which is optimal.

 

So the formula on crutchfield is wrong? http://www.crutchfield.com/installguide ... gauge.html

 

That table is pretty much dead on with the info I gave you. I was just classifying it more specifically.

Use 8GA or better cable, that lists 50A@20' on the edge of 8GA, which you might be better off with 4GA, just for voltage integrity. It's better you use it than drop it.

 

what he said

 

You don't want to go too high on the amperage of the fuse because then it may not blow soon enough, and potential damage to your equipment and/or vehicle could occur.

Use this equation: P=I*E, where P=power (400W), I=current (unknown), and E=voltage (12V). Solve for current. Take P/E (400W/12V) = I = 33.3A. You'll want a 40A fuse optimally in that configuration, possibly a 50A if your amp overdrives. Most likely, your amp has 40A worth of fuses on it already. The more overrated the amperage on a fuse, the longer it will take to blow. When a short occurs, the current doesn't instantaneously reach infinity. Integrated circuits require nanoseconds to switch between one another. If that surge of current reaches through and blasts a gate that cannot handle it, or any electrical component, then it may blow that IC or component. Nanoseconds of difference is what you'd see in fuse reaction times when one blows. Nanoseconds is all it takes to potentially do damage, whereas none may have been done before.

Now, using some equations I know, if you're using a copper wire, 10AWG will drop ~16% of its voltage at the end of a 20' length, based on 40A maximum current. 8AWG will drop ~10%, which is a grade of wire commonly used up to ~600W (and it will work). 4AWG, however, will only drop ~4% of all voltage, which is optimal.

You are the ohm's law master superh and I concur use a 40 amp fuse.

 

i ran a 200a Blade fuse on 2ga to my JBL BP1200.1 off my stock Ford Focus. very sick setup i had. 1x12" Adire Brahma MKII sub. WOW, was it loud. cant wait to hear it in a truck soon.

 

i ran a 200a Blade fuse on 2ga to my JBL BP1200.1 off my stock Ford Focus. very sick setup i had. 1x12" Adire Brahma MKII sub. WOW, was it loud. cant wait to hear it in a truck soon.

200A fuse? I hope your amplifier had protections for power surges up to 200A, like a fuse onboard (like most have)!

The reason to choose a smaller fuse is because you want to *protect* your equipment in case something bad happens, such as a smashed cable causing a short, causing current to increase and potentially damage your amplifier!

 

the jbl amp comes with 3x40a fuses and it has clipping prot. i was able to hit a 139.X on the old therm lab mic with Crystal Method - High Roller Song from my Brahma in a 2cu. ft SQ ported box.

EDIT: the reason i went so big on my fuse is because i had 4ga w/ an 80a glass fuse and i could blow it every time. had my system checked and it needed at least 99a fuse, so i said ahhh what the hay, go big or go home. i have alot of room to upgrade now

 

Go big or go home isn't the best in this case. You don't want to oversize a fuse or breaker by that much. Of course it will work, but there are occasions that you want it to blow, that is it's job.

"Right sizing" is the best approach in this case.

 

it all depends... i ran multipal amps for different SPL comps. so i needed at least a 150a fuse. when you knows things are going good after 2 solid years, its fine. i dont believe in the RIGHT size fuse anymore, i hate replacing them from time to time. Id rather blow an amp, which i know i wouldnt, because i know the limitations. i was a big spl guy but im leaving the scene now, its way to expensive.