Threshold S/300 power amp problems

Does anyone have an idea what the problem might be where the power amp does not continue to provide sound? While I was working in my office and listening to Bill Evans Trio there was a sudden pop sound (not loud because I was listening at a rather low volume) and then there was no sound. There was/is a slight static sound emanating from the speakers but nothing else. The main pilot light on the Threshold remains on but does not produce sound. I have:

1. attempted to play the CD player.
2. attempted to play the reel to reel tape recorder.
3. checked all cables and connections.
4. made certain the pre-amp volume was turned up.
5. checked all fuses on the power amp. All looked good.

I was not able to get any music out of the system. I will swap in my Audio Research power amp this weekend and see what happens. Thanks for your comments.
Not to make your day more difficult, but why do you assume it was the amp? If you are hearing any sound from it at all (slight static sound) it may be working, just not getting a signal from the pre-amp.
I agree with Newbee.

Check your preamp.
Thank you Newbee and Tvad,

You are both right. I had given that some thought but not very seriously. I can eleminate that possiblity by swapping in my standby Audio Research power amp. If I don't get any play I will then know the pre-amp is the culprit. Thanks again guys.