Hot plug USB speakers + Airplay

I recently purchased a Raspi 2, installed volumio and this far, I’m very happy with my experience. I was able to set up Airplay pretty easily for my USB speakers (Samson Studiodocks). The problem that I have right now: I want to keep the Raspi running all the time, but have to turn off the speakers (over the day when I’m out of the house, during night because of the bright status light).

When I want to turn the speakers on and play music via Airplay, the system just refuses to work. iTunes tells me that an unknown error occurred and nothing besides turning the raspi off and back on works.

Is it possible to do this kind of thing? Or should I turn the raspi off everytime I don’t have my usb speakers running? I tried the 3.5 mm jack, but was turned off relatively quickly due to a high amount of background noise/buzzing that occurred all the time (maybe possible way to fix that?).

Thanks for your suggestions,

Edit: Additionally, I’m able to access volumio.local/ at all times and the right output device is set too!