Help me understand amplifier current draw and watts

[Based]

Ok so I read somewhere that you can kind of tell if an amp puts out rated power by looking at its fuse rating.

An amp I'm looking at has a fuse rating of 160A. So that means it draws 160 amps right? It claims to do 1350rms at 1 ohm and an efficiency of 85%. So if the amp draws 160 amps at 14.4 that means it should do like 2300 watts if my math is right. I guess that is PEAK and not RMS?

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[JohnKuthe]

Ok so I read somewhere that you can kind of tell if an amp puts out rated power by looking at its fuse rating.
An amp I'm looking at has a fuse rating of 160A. So that means it draws 160 amps right? It claims to do 1350rms at 1 ohm and an efficiency of 85%. So if the amp draws 160 amps at 14.4 that means it should do like 2300 watts if my math is right. I guess that is PEAK and not RMS?

A car audio signal varies a lot. Specs are normally given as some objectively measurable constant state signal, not what YOU are going to play.

Staying well below the stated specs is always safest. Do you fully understand the differences between peak and RMS power ratings? If not just stay well below them and your system will be better off.

John Kuthe...

 

[LosIsATool 5,000+ posts]

It's a good indicator but not absolute. Some brands are now using "spare" fuses to trick people. Price is a better judge of real power

 

[n2audio 5,000+ posts]

Ok so I read somewhere that you can kind of tell if an amp puts out rated power by looking at its fuse rating.
An amp I'm looking at has a fuse rating of 160A. So that means it draws 160 amps right? It claims to do 1350rms at 1 ohm and an efficiency of 85%. So if the amp draws 160 amps at 14.4 that means it should do like 2300 watts if my math is right. I guess that is PEAK and not RMS?

If you use those numbers you'd have around 1900w (with eff of 85%).

So unless this is a dirt cheap amp with a phantom fuse or some rare BS like that, all those calculations (approximations) tell you is it appears to be accurately rated.

Efficiency ratings are pretty vague, too. They probably aren't spec'ing it with the amp under a lot of stress like high volume at 1 ohm. When a mfg makes a big deal about high efficiency they're usually referring to the most ideal operating conditions which is no where near what you'll have in a car.

The fuse rating calcuation is a VERY rough estimate. It is most useful for bottom dollar shoppers looking at low end Boss/Crunch type stuff.

The Boss ar4000d for instance. Rated for 3000w rms at 1 ohm, uses 3x40A fuses and costs $105. Obviously that's not a 3000w amp. Based on the fuses it's probably in the ~1200w range. Based on the price it's probably an unreliable 1000w amp.

 

[Based]

A car audio signal varies a lot. Specs are normally given as some objectively measurable constant state signal, not what YOU are going to play.
Staying well below the stated specs is always safest. Do you fully understand the differences between peak and RMS power ratings? If not just stay well below them and your system will be better off.

John Kuthe...

how do I get RMS from peak? A quick Google search says you can just multiply your peak by .7 and get RMS.
I just did a test. A hifonics 1200 has 2 70a fuses. 140*14.4 = 2016. 2016*.85 = 1713. 1713 peak * 0.7 = 1199 rms.

A BOSS 1100 amp has 1 30a fuse. 30*14.4 = 432. 432*.85 = 367. 367 peak * 0.7 = 257rms.

Maybe I'm wrong idk.

 

[JohnKuthe]

how do I get RMS from peak? A quick Google search says you can just multiply your peak by .7 and get RMS.

That's a pretty good approximation. It's not mathematically analytically correct but a pretty good approximation. like 3.14 is for the number Pi.

John Kuthe...

 

[JohnKuthe]

...Maybe I'm wrong idk.

You are fine, and learning! The equipment is just equipment, neither right or wrong. Just IS!

John Kuthe...

 

[Based]

You are fine, and learning! The equipment is just equipment, neither right or wrong. Just IS!
John Kuthe...

Yes I am learning! I'm just trying to make an informed decision on an amp.

 

[Based]

How do I calculate what it "should" do at more than 1 ohm?

 

[Based]

The issue I'm having is ok if 14.4v * 140a = 2016w. But ohms law says amps = volts/resistance. So if the voltage is actually 14.4 then 14.4/1 is only 14.4 amps. I'm just confused. I have a hunch that I am confusing DC volts with AC in this case.

 

[LosIsATool 5,000+ posts]

Don't put so much thought into it. Power is always changing anyway. Imp rise, dynamics, voltage. Just buy known, proven, reliable power

 

[Boomin_tahoe 5,000+ posts]

All those things can be found online. Even youtube vids. Hell anything is possible with the web.

 

[Based]

Ok so I have a pioneer 1200 watt amp now. It does 1200rms @ 1 ohm. 1200w/14.4v = 83a. So why does it have 3 40a fuses? Is that because it's peak power is probably around 1800w? Right now I have it on 10 feet of 6 gauge wire with a 100a fuse. Nothing gets hot.

I'm trying to understand this before I buy a bigger amp so I know what size wire I need and what fuse.

 

[ilikeradios 10+ year member]

Most of the amps I own do not have fuses.

You are putting too much thoughts on what the fuses are.

If you want some cheap power get the CAB 1600.1 or Skar RP2000 neither amp has on board fuses, not that it matters.

 

[kr15 5,000+ posts]

Keep in mind, unless you have stellar electrical, you wont stay at 14.4v.

At 1ohm and stock electrical, i bet that pioneer would drop down to about 12.8v

Less voltage= more amperage required. Also, the lower load an amp sees, it usually gets less efficient