Sound jumping from normal volume, to extremely low.

So for the past few days, whilst watching youtube or playing a video game, I have noticed that my computer's sound has bounced from normal volume to extremely low. Nothing seems to effect it, as it does it randomly. I have changed out wires, and speakers (I only have my center speaker hooked up as I am moving soon and didn't want to wire up the entire room). It is not the speaker, the wire from the computer to the amp, or from the amp to the speaker. Now the sound seams to be stuck at the low volume, and I can only hear the bass unless I turn the volume up- in which case it sounds fuzzy. JVL audio wave series HD 707

Thanks for the reply, yes headset works in both front and rear port, I also hooked my surround speakers up and they work fine. It seems to be only the center channel. I connected my center speaker to another output (front left I think it was) and the speaker works fine.

Center by itself has worked correctly for the past month. The entire surround is connected and the center is still low volume while the rest of the system is at full volume.

Ok sorry let me break it down. I have a cable running from my green jack to the bass, which distributes the rest of the wiring to the speakers. I only had my center speaker hooked up at first, but when all my efforts showed that I couldn't fix it, I hooked up the full surround. All speakers work, and when I disconnect the center speaker from the center output, and say, reconnect it to any other output- the speaker works. It looks like for some reason the center output is not working correctly... May be that the output directly from the bass isn't working properly... I hope not hah.