I had a question regarding the amount of power an amp would draw. For example, if I had a 4 channel amp which required a 60 amp fuse, but I only use two of the channels, does that mean the amplifier would only draw 30 amps of power from the alternator?

 

Not really, either way the unused channels still are using current, just a lot less.

 

the amp needs to draw power to make power and the power draw depends on the load which you run the amp at.
for example the amp puts out 1000Wrms at 4 ohm's and is rated for 1600W at 2 ohm's.
the amp will draw roughly 100 amps at full tilt while the amp at 2 ohm's will draw 160amps...roughly
i believe its about 1 amp per 10Wrms.

so current draw depends on the load on the amp and gains and bass boost and all that stuff.

so look up the specs on your amp to see what the ratings are.
go to ampguts.com

 

OK the reason i asked is because my car has a stock 120 amp alternator and I dont want to upgrade any of the electrical system. So should I look at getting a smaller amp that would only draw around 30-40 amps?

 

Don't worry about that, you can't just use amperage as a factor. You're forgetting voltage, total wattage, amp efficiency, etc. Its a headache and a half to try to figure out, I will be running 2500w on a stock alternator, so you should be fine

 

The amp I will be getting is the Rockford Punch 450.4. How will this affect my stock 120 amp alternator?

 

just hook it up and go. There's nothing to say that you're not going to be ok.

 

Most good amps put the power draw specs in the manual. Doh!

My 5100T's say they could max draw 30 amps, but it also says *19 amps average.

*Average current drawn
• The average current drawn is nearly the maximum current drawn by this unit when an audio signal is input. Use this value when working out total current drawn by multiple power amplifiers.

In other words, you can't draw max current with music. Unless your at full clipping, which would have fried all speakers, then they wouldn't draw any current anymore?

So, why do they have two 30 amp fuses?

I run six 5100t amps (not all bridged) and there is no way i can blow a 100 amp fuse, running off the stock 140 amp alternator. That includes the HU, interfaces & 3F cap all on the 0 ga. with 100 amp fuse.