New Mac Mini (late 2014) sound input - says "No input devices found"
Try this:

Resetting the SMC and PRAM for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve

• Shut down the computer.
• Unplug the computer's power cord.
• Wait fifteen seconds.
• Attach the computer's power cord.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need them in next step
• Wait five seconds, then press the power button to turn on the computer.
• Press and hold the Command-Option-P-R keys before the gray screen appears.
• Hold the keys down until the computer restarts.
• Release the keys. 

Read more: http://www.justanswer.com/mac-computers/65d0r-mac-osx-no-sound-no-input-output-devices-found.html#ixzz3XNRpChvF