Originally posted by KnuKonceptz:
Actually the resistence in the wire is one of the reasons why you want bigger cable. How else do you account for voltage loss between the battery and at the amplifier. There will be a loss, it of coarse depends on the current as well. But the cable itself has to have some resistence, how can it not?
Yes, the wires do have resistence. This is exactly why you have different gauge wire requirements for different lengths. But it is usually not taken into account for calculating current draw because it's relative resistance is so minor compared to a 4ohm load, for example. A one ohm load would get a lower percentage of the power compared to a system with a 4ohm load, if the total current were the same.
At 100 percent efficiency maybe yes, but what amp is 100% efficient. A class AB is at most 35%, the rest is turned into heat. To even that equation out (my math is rusty, sorry) 100/35=2.857 31.62*2.857= 90.28. Maybe thats not the way to arrive at this solution, like I said its been awhile but no way does a 1000 watt true power amp draw 31 amps. Fuse ratings for PPI A600 is 60amps, a Hifonics Zues (old school seies 6) was 80amps and it would blow those fuses all day. I have an inductive amp probe (meter that clamps around the power wire), on a class D rated at 1000 watts the amp drew a peak of 123amps at clip. I know for sure it was not putting out 6400 watts.
31A that I calculated / 35% efficiency = 88.6A current draw. That's my confusion, then.
123A draw at 35% efficiency = 43A into 1ohm for example is 1853w actual output.
I see what you are saying about the AC voltage coming from the amps output. That is not relivent, (maybe relivent is a bad word to use, maybe not required instead) but the DC voltage from the car is. The power supply is demanding from that and amplifier power supplies run off DC current from the car. The amplifiers demands are the amperes that are traveling through the power wire. That is what should be calculated.
True, and see next post.
Wonder where Dave is...
