Channel Seperation Issues

In answer to Rwwear, the bass line is played by a Fender 4 string bass guitar with plenty of lower midrange to localize the sound. I believe, at least.

To Tarsando. Everything else is not divided properly. I spent the afternoon fiddeling around more. Changed speaker cables completely to some very short 3' oldies I had lying around, and playing music to see if I could narrow down the issue. On Dark Side of the Moon there are footsteps running from left to right and back again very clearly, I could not localize them properly. On Led Zepplin's Whole Lotta Love, there is similar swirling around between left and right in the mix, and that is not localized well either. On tracks with a single singer, the person is centered up fine, sound stage is apropriatly deep and or wide as the mix dictates.
Interesting thought on the mono switch, but no dice. At least not to my knowledge. Although I could see myself making that type of mistake! The amps bias up well. Everything else SEEMS to be in order, but I can't kick the problem.
Could I be starting to lose a driver or input tube in the right mono-block? Would the beginings of that cause a problem such as this? I need some solid Tube Afficianado advice perhaps.

Thanks very much to Rwwear and Tarsando for posting in, I very much appreciate your thoughts and time. Any other ideas from you or anyone else would be MIGHTILY appreciated.

NGjockey-

All drivers seem to be working.

Are the speakers themselves out of phase--as opposed to phase-reversed? Swap leads on just one speaker--have you done that? Find a mono cd or lp and see if it's centered. What's NEW in your system? If it's ALL new, (ie new to you) then no help, but if you installed a new piece, take it out and put the old one back in. Play just one speaker at a time--I would think a loose tube or bad tube would do more than mess up the localization...it should sound crappy on its own. Does the cd player have a headphone output that you could use to bypass the preamp and test it that way? Good luck finding it!

The only thing that comes to mind is where the xover point is for the side mounted woofers for the Audio Physics. If the point is too high, the side mounted drivers may be diffusing the upper bass therefore mixing the left and right somewhat. I would make sure the speakers are far from the side walls and perhaps toe them in to where you can't see the sides of the cabinets from your listening position. I would also try to get them as far apart as possible without getting too close to the side walls. My speakers are about ten feet apart but toeing them in gives me plenty of center fill. I do not have the same brand speaker as you so you may have different results.

Many thanks again Rwwear and Tarsando for your time!
Swapping leads on just one speaker is interesting, I hadn't considered that. No headphone jack on the CD or anywhere else, unfortunately, but I'll try the one speaker lead switch. The Pre is new, but I swapped it out already and the problem contiued.

If any other great minds out there have an idea or hunch, please let me know!!!