Optical Audio connection stopped working on Apple TV

Hi,

I recently bought an amplifier and speakers to hook up to my Apple TV so I could use those for sound instead of the speakers of my monitor/tv. My current setup runs an HDMI cable from the Apple TV to the screen for video, and an optical audio cable directly to my amp.

This setup has worked fine since I bought the amp about 2-3 weeks ago, but suddenly this week the audio through the amp has stopped working. When I turn it on and try to play a video/music/anything with sound through Apple TV I hear a loud pop and a buzz/hum coming from my speakers. I have tried replacing both the speaker cables and optical audio cable but this has not helped. I can still run the sound through the TV which works fine. I'm not sure why the sound through my amp suddenly does not work anymore, has anyone had experience with this?

Thanks