Hi, I have a subwoofer (Dayton Audio RSS315HFA-8) that is connected to a subwoofer amp (Dayton Audio SA230), which is connected to a receiver (Sony STRDG920). At some point a little while ago, I stopped getting any sound through the subwoofer (i.e. it had previously been working fine). I am trying to figure out the issue, but I am not really sure how to go about determine whether the issue is the amp or the receiver without needing access to an additional amp or receiver. I was able to hook up the subwoofer to another source, so I am confident that it is not the issue. Also, I confirmed that the receiver is set up for 'small' speakers and the crossover frequency is 80Hz. What other steps would you take to determine the problem? Is there some type of equipment that I could get that is relatively cheap that would help me diagnose things further? Thanks!