Stereo sound stopped working
 

Hi everyone,
I'm new to this forum but have been reading it for a few months for info. I have an 06 Sentra spec v and recently the stereo has no sound. It has the "upgraded" Fosgate. The stereo comes on and all functions work but no sound. How do I test the amps? as this is probably where the problem is. It just stopped working one day. I have a new Pioneer cd player to install but figured it was pointless until I have sound. Thanks