Ok noobs, here is some simple math that may or may not help ya in life. If anyone has comments or corrections please post them up! This does not always work out depending on the amps design but on most class a/b it works out pretty often!

#1 How to quickly determine an amplifiers general max and rms output with no info on the amp other than a factory fuse rating. "in case that wanna be car salesman of a car audio guy with greasy hair tries to push that new chrome ghetto 4000W amp on ya"

All manufacturers 99.9% of the time fuse there amps at there max power before the amp can be damaged. Peak power on a class a/b is usually double the rms rating. So if you come accross an amp that has a stock 50 amp fuse in it you would multiply the fuse rating by around 13.8 vehicle voltage to get the max power the amp can produce so 50amps x 14.4 = 720W peak power. Now if you want close to the rms rating then divide the power by 1/2 so 360W rms approx +/- 50 watts or so.

Class D amps do not usually apply here.

Most noobs have to remember it takes power to make power.

You can also take wattage divided by voltage to get amperage as in 720 divided by 14.4v = 50 amps of current draw. This helps when determining if your charging system us up to par! Say your 3 amps can produce on paper 1200W of power. Take that 1200W and divide by your vehicles running voltage "take a meter to the battery" which is probably 13.8 or so and divide it. Gives you a total of 86.95amps of current draw. 1200w divided by 13.8V = 86.95

Now when your at a stoplight and think you need to show off for that **** blonde chick next to you.. you do not want a fuse to blow right? Then you would look like an even bigger tard. So give yourself some headroom and install a fuse close as possibly to the fuse ratings on both amplifiers. Or as I do it, on a 86.95 amp draw max clean power I would slap in a 100amp fuse or breaker which should be plenty. if you find yourself blowing a 100amp fuse all the time, your cable is good, the grounds are good and your total current pull should only be around 86.95 then congrats!!! YOUR A BASSHEAD, OR YOUR EARDRUMS HAVE ANOHTER 10 MINUTES BEFORE BLEEDING FROM THE ROCK'N'ROLL ECT.. Either put in a 150amp fuse or get larger amps so you stop clipping the ones you have. Who knows, clipping them that bad could melt your nice carpet!!! "caugh caugh orion hcca 225..." oops did I just reveal how long I have been doing this crap haha??

Next time you see that flashy chrome plated super ghetto 4000w amp on the shelf and see it has a 25 amp fuse you will get the real picture real quick of what it can actually produce powerwise. Good luck and happy installing.