Hey all,   I own Beyerdynamic 990's and am considering buying an amp for them.   But the Engineer in me is bothered...  Why should high impedance phones need a bigger amp?   I can see that you need more voltage for a given volume level.  P = V^2 / R so twice the impedance requires...

Hello all,   I own the latest 990 600ohm cans, and I love the sound!  Unfortunately, I don't love the headband.   I also own the older 990 pro and 880s.  I stuck with Beyerdynamic partly my old phones were super comfortable, and the replacable ear cups and padding are a bug plus.  ...