Several months ago I woke up one morning to no subwoofer volume even though I had clear, full volume sound from all 5 of my satellites.  After shutting the power off to the amp for approx 10 min it worked again with no issues until the next day when it had the same problem.  This continued to get worse over the next week until finally nothing would restore sound to my subwoofer unless I had my computer volume at full and my external volume control at 65 or above.  The higher the volume is the clearer it seems the subwoofer sound gets as well.  Now I like bass, but my neighbors are going to murder me if I listen to music all day long at that volume level.

I have read a few posts regarding issues with sudden intermittent sound from the subwoofer leading to eventual loss of sound and one of the apparent problems is bad MOSFETs.  I tried replacing them as this is the simplest and cheapest fix I saw around and had seemed to have a high rate of success for most, but this didn't fix my problem. Luckily, at least, the problem did not get any worse upon replacing the MOSFETs so I'm pretty sure I didn't ruin anything.

I've tried searching further and have come up against a wall regarding finding out where my failure is and what I need to replace to get them back in working order.  I miss my subwoofer :(   Help please?

my guess would be the op amp is defective.

 So, essentially, there is nothing I can do but replace the amp?  Do I have any cheaper alternatives?

Well you could always bust out an oscilliscope and walk through the circuit and fix problems as you come across them. Might wanna map out the circuit in the process so you can understand what things should be doing.

It's not like there's a magic fix-all for any possible problem you might be having. 

Good luck. 

 Unfortunately I'm not that electrically inclined.  More along the lines of the basics like soldering, etc. hehe.  Never hurts to hope for someone who has had a similar experience and some luck fixing it but I definitely understand that there is a lot more involved with this issue and, like you said, there isn't really any sort of fix-all aside from just replacing it outright.

 I do have access to an oscilliscope so I could try to walk back through the circuit.  I can get a general idea of the function of the circuit from my limited (VERY) knowledge of electronics so I think if I spent a bit of time researching I could get a pretty solid idea of where to start.  It will be interesting familiarizing myself with the oscilliscope again as I've really only ever used one for aligning microwave antennas in the past =/

 Do you, or anyone reading this, have any pointers or tips for me as I try to delve into all this nonsense?  It will, at the very least, be a good project heh.

 Thanks again for the info. 

Well first get a tone generator to, pump in a low freq some thing around 80hz i think, dont remember what freq the sub works at, and start from the begining and move your way up. or start from the end and move your way down. Like i said it might be a defective op amp " its operational amplifier" or maybe one of the resistor or capcitor combo is defective for some reason.