I have had issues with my amp, had the original replaced just after a year for free thanks to Klipsch, the replacement failed 3 months later. They claim its not a common issue, but I beg to differ, there were threads after threads of people having issues with their Ultra 5.1, they have since been discontinued quite a long time ago, no doubt because the design was poor and the amp was not designed by Klipsch, so there ya go!
My amp has been hissing on and off for several weeks now and tonight I thought id switch it to HP(headphone) mode thinking it would leave the amp in a normal state but let me effectively mute the system without turning it off. To my surprise(somehow) it didn't work and now its got a high pitched whine to it and its a huge hit or miss if leaving the power cable unplugged for an hour or all night or simply turning the system on and off several times would cause it to function.
Guess its time to find a schematic and get sodering... sad too, best PC audio system made and the amp is a POS. But buying a 5.1 500W amp is around $500 so... in order to make the system affordable they had a POS amp from who knows where installed in the system.