This is a simple one and I've seen it mentioned throughout the forums but can't find a definitive fix... First off, I was wondering (kind of off-topic) why OS X makes audio output so... difficult. With Windows, you plug in your headphones and sound immediately switches to headphones. With OS X, it's a whole process - you have to plug in the headphones, wait several seconds for the Mac to recognize them, and then press the F12/F11 buttons several times to "kickstart" the audio output. Anyway, being impatient and previously annoyed with my computer, I plugged in my headphones a few days ago (I use headphones a lot) and immediately started banging the F12 key. Since then my MBP has apparently decided to get revenge on me. Every single time I plug in my headphones, wait patiently, and then press the F12 key, it shows the volume at full but with a Ø, and I can't change it. Weirdly, going into Sound in System Preferences, I can easily change it from there with the slider. Then, after several minutes, things go back to normal and I can use the F12/F11 keys with my headphones. What is this and what have I done to upset my computer? Thanks.