I am using mbp 2011 early version 15' and recently found out 1. while charging....mbp gets more hotter enough to make fan runs about 3000rpm while not doing any tasks. 2. using a dac(which gets power from the usb port)with mbp for listening to music also makes mbp more hotter, thus makes more fan noise than using internal mbp speaker. 3. using a dac also consumes more battery. I fully charged the battery and played songs using dac and active speakers untill battery went down to 10%. It tooked only about 1 hours and a half. 4. very same situation like number 2 and number 3 except for this time its not dac but using a external monitor thru mini dp. so in conclusion if i try to watch a full hd movie using mbp with my external monitor connected and active speaker, the fan goes crazy. what do you think?