Calculating current

[MkKin420 10+ year member]

What is/are the formula/s for roughly finding amplifier watts and figuring efficiency into the equation? Correct me if I'm wrong but I'm pretty sure its Volts x Amps (fuse rating) x estimated efficiency. I was trying to figure out how a few amps were rated, weather they were under or over rated such as the Hifonics 1208d. The fuse is 80a and the amp is rated at 1200 Rms at 1 ohms. 14.4*80=1152 without figuring efficiency, is that right? But if I look at the Alpine Mrp m500 it has a 60a fuse and is rated 500 rms at 2 ohms. 14.4*60=864 864*.7 (.7 as a rough guess of its efficiency)=604.8 this falls well within its rated Rms power. How is this?

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[roarzorz 10+ year member]

Sounds like you have it. A general rule of thumb I go by is take the fuse rating x 10 and that's the rough power output.

 

[MkKin420 10+ year member]

Sounds like you have it. A general rule of thumb I go by is take the fuse rating x 10 and that's the rough power output.

Thanks for the reply. I like your rule of thumb, 10x the fuse rating, it seems to work with most of the CEA rated amps / well reputed amps. I've just been browsing through amps looking for the best for my buck. Both ways work alright, yours comes in handy for quick estimates since neither is going to be dead on correct. THanks.

I did some of the math with the Sundown SAE 1200d, as well as the SAZ's, OMG what a great amp. If I had the cash I would buy that amp in a heart beat. That thing will do at least its rated power at 12.8v that things a monster.

 

[roarzorz 10+ year member]

I did some of the math with the Sundown SAE 1200d, as well as the SAZ's, OMG what a great amp. If I had the cash I would buy that amp in a heart beat. That thing will do at least its rated power at 12.8v that things a monster.

Keep in mind that Sundown amps are close to 80% efficient @ 1ohm . They'll easily do more than rated @ 12v. The sae-1200d is good for 1500watts.

If you want to get more technical and precise use a clamp meter on the power input and read the DC current draw. Also use a volt meter at the power & ground terminals to read the dc voltage input at it's lowest point after drop. Then multiply those #s. Now move your clamp to the + speaker output and measure the AC current ouput. Use the volt meter on the + & - speaker output to measure the AC voltage output. Then multiply those output #s. Divide the input measurement into the output and you have actual efficiency.

 

[MkKin420 10+ year member]

Keep in mind that Sundown amps are close to 80% efficient @ 1ohm . They'll easily do more than rated @ 12v. The sae-1200d is good for 1500watts.
If you want to get more technical and precise use a clamp meter on the power input and read the DC current draw. Also use a volt meter at the power & ground terminals to read the dc voltage input at it's lowest point after drop. Then multiply those #s. Now move your clamp to the + speaker output and measure the AC current ouput. Use the volt meter on the + & - speaker output to measure the AC voltage output. Then multiply those output #s. Divide the input measurement into the output and you have actual efficiency.

THank you man. It can be hard to get that in depth of an explanation on here. I will keep that in mind, I need to pick up a clamp and a new volt meter ASAP anyway. I need to save my cash and invest in a Sundown amp. Thanks again.

 

[IDSkoT 5,000+ posts]

Sounds like you have it. A general rule of thumb I go by is take the fuse rating x 10 and that's the rough power output.

The actual generalized equation is fuse rating * Voltage * .8 (For efficiency)

But, fuse rating * 10 works, too.

 

[MkKin420 10+ year member]

Of course were talking about Class d amps only right? AB amps stand no chance of reaching that kind of efficiency.