WyllyWylly

Steve(nwithaV): those are the right ones. It can be done with one pair of hands, but two pair and a bright light are recommended!

Thanks Habersham, your post was more helpful than you give yourself credit for. As far as testing, it is not affected by either the PC volume controls nor the control pods volume pot; it does not emanate from the computer the sound persists when the computer is turned off and even unplugged but the speaker system is on; and it does not appear to be related to noise on the circuit. I have disconnected all electrical devices from the circuit the amplifier is connected to and the hum remains. I have also run an extension cord to a different circuit in the home and the hum was still present. The headphones themselves are hum-free when attached to any other source, a relief given that they're fairly high-end Sennheisers. I'm unclear on the relationship between the control pod and the amp; my thinking is that if the hum is in the headphones straight from the pod, that's where it has to originate - somewhere in the preamp circuit. That makes sense to me because the amp would pick up any hum in the preamp circuit; what I don't fully understand is why it is not affected by the volume pot. It's just... there. Based on your input, it sounds like it's cap-sweep time. That can't be a bad thing regardless, I bought the system new about one year after it was released so it's got some miles on it, and as you mentioned... caps are cheap. Thanks for the link, I'm going to break out the multimeter and soldering pencil and get to work.

Would this also apply to the original ProMedia 5.1s? I suspect the control pod because the humming in my rig is in the headphones with the main amp disengaged... old swelled up caps are a sure bet given the age of my system, but I confess that I don't know exactly how the pod interacts with the amp... I always assumed it was a preamp of sorts. Would I be hearing a constant hum (regardless of volume) in the headphones even though the amp is disengaged? On a side note, I've always hated the pop in the mains when switching from the headphone jack. Shame there's no easy way to fix that since I'm cracking the board anyway.