Okay. Sorry this is so long.
The problem I'm having is a very dry, reedy, over-emphasized upper midrange, on particular pieces it's discer0nible as trace amounts of electrical-sounding interference -- not unlike the audio equivalent of those little traces of snow you'd see on the TV when dad was in the next room running the electric carving knife.
When it happens, I can *sometimes* fix it by powering-down and disconnecting everything and the powering up again.
As a late-breaking update, when my problem is occurring, I can feel what I had always thought was a faint vibration on the front aprons of both the amp and preamp. Recently I discovered that when the problem isn't occurring, I couldn't feel the "vibration."
I hadn't thought much about this aspect, one way or the other, until last night -- when I realized that I could still feel it after powering everything down. I'm thinking this suggests that it's not a vibration at all, but a very, very faint electrical discharge, leaving the front apron of the two pieces and traveling down my hand into ground.
In answer to your other questions, there is a big-*ss plasma TV in the rig, but it isn't connected to any subscription service of any kind, cable or satellite; it's just for movies. The rest of the rig consists of:
An Arcam FMJ-CD23 cd-player
An Oppo DV-980H, discrete analog six-channel DVD player
A McCormack MAP-1 multichannel preamp
A McCormack DNA-HT5 multichannel amp
A Hsu Research VTF-1 powered subwoofer
Power cables are by Element Cable (CD player and Preamp), and Harmonic Technologies (Amplifier).
Interconnects are by Blue Jeans Cable (between preamp and amp) and Element Cable (between CD-player and preamp).
Speaker cables are cross-connected twisted pair, by Element Cable.
Speakers used have included Linn Ninkas, Audio Physic Spark IIII's, Totem Mite-T's, and Linn Katans.
RF treatments include self-adhesive copper sheathing inside the CD-player, an Eancom plug-in filter, power wraps on the power cable for the CD-player and sometimes on the interconnects between the CD-player and the preamp, snap-on ferrites the stock power cords for the DVD player and the subwoofer, and short plugs on the unused input sockets of the McCormack.
The power in the house pre-dates the three-pin technology and, despite the fact that the outlets have a third pin, that third pin isn't actually connected to anything.
I'd thought that a dedicated and properly-grounded AC line would fix everything, but I recently took the whole rig to a friend's relatively new house on the quiet side of town, far from most common sources of RF, and everything sounded just as terrible as it so often does -- and in the same ways -- as in my house with my antiquated wiring.
I might also point out that I've had problems that aren't exactly the same but aren't completely different, with earlier solutions for amplification, too. Three years ago when my Parasound separates started acting fritzy, they exhibited the same pattern of acting up intermittently, and I could sometimes -- but not always -- make them behave normally. In that case, one channel would get cloudy with background hiss, then cut out altogether, and if I walked behind the rig and wiggled the interconnects, the sound would come booming back in and stay that way for a day or two afterward.
Then I got a Naim Nait5i which would overmodulate the low midrange intermittently, and whose input selector would freeze whenever I detected the midrange problem.
Then I got an Arcam integrated that couldn't make decent sound under any circumstances in my own house, but sounded fine at my friend's place.
And now this.
On several occasions I've had various pieces of gear serviced, and always they come back un-modified because, "we couldn't make anything go wrong, here."
Really, if all of this doesn't add up to one, obvious solution pretty quick, I'm gonna fire-sale all of this crap and replace it with two Aiwa bookshelf systems with external inputs for the signals coming from the Oppo, and just be done with it all forever. This stuff was *horrifically* expensive, was supposed to make me happy, and now I'm completely unable to listen to it, and the laughing-stock of my friends to boot.