Guys one more question
Is this right calculation?
V=3.57771
mA=111.8
R=32
W=0.4
V=5
mA=8.33
R=600
W=0.04167
Or if iCan is class A, so on higher impedance load will it produce more power?
The iCAN is able to output a maximum 5V. However, there is also a maximum current which is apparently about 111.8mA (approx.)
So with a 600ohm can, there is no current limiting.
However with a 32ohm can, current limiting sets in when the voltage reaches 3.57771V (approx.)
Remember that the loudness of a headphone depends not just on the amount of power but on it's sensitivity.
The iCAN doesn't appear to put out a lot of power into a 600ohm beyerdynamic T1 but the T1 produces 102db/mW so the available 41mW can drive the T1 very loud.
Maximum power from the iCAN is available into a 45ohm load as this is the impedance at which 5V produces 111mA of current.