Power ratings on amps

These four values are interconnected and having them you can do the math and get any one of them.

Voltage (Volts/E), Wattage (Watts/Power/P), Resistance (Ohms/R), Current (Ampers/I)

Having two of these values you can always get the third one.

It is all based on Ohm's law:

OHM'S LAW
BASE FORMULAS P=I*E E=I*R
TO FIND VOLTAGE E=P/I E=I*R E=SQR(P*R)
TO FIND CURRENT I=P/E I=E/R I=SQR(P/R)
TO FIND POWER P=I*E P=E2/R P=I2*R
TO FIND RESISTANCE R=E2/P R=E/I R=P/I2

P = Power in Watts
E = Electromotive Force in Volts
I = Electrical Current in Amps
R = Electrical Resistance in Ohms
SQR = Square Root

Check these links to have a better understanding:

http://www.bcae1.com/ohmslaw.htm

http://www.kc9aop.net/Doc/link_pages/Ohms_Law.htm

http://www.sengpielaudio.com/calculator-ohm.htm

I was reviewing this myself recently for the same reason you are doing it now :)

Quote:

Originally Posted by estreeter 

     For example, if the Fiio E9 has a rating of '1 Watt' ('16 ohm loaded') and the iBasso P4 has a stated output of 600x600mW into 32 ohms, what is the conversion from the Fiio figure into something I can compare with the P4 32 ohm figure ? Help :)

 

 

Deferring of course to Ohm's law, there are some generalizations you can make.  As the load impedance doubles, output power will roughly halve.  In the case of the E9, if it delivers 1000mW into 16 ohm, it will likely deliver 500mW into 32 ohm.