"speakers have been moved in every direction possible and the end result is always the same : center imagining and that is where it ends. "
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something is wrong with connections, externally or internally.
L/R MUST be working equally to create a center image which is entirely Phantom.
It sounds like something is in MONO mode, OR something is wrong with your l/r connections. out of preamp to amp; speaker connections. OR, inside the preamp. OR inside your amp.
1. Double Check all your connections, find something wrong, fix it.
2. double check all tubes: in correct sockets? (I switched my 6sn7 with 6sl7 once)
3. Prove AMP is producing Stereo (omit preamp). Hook up a CD player (any line level device (not LP) directly to the amp . Nice imaging? IF so, speaker wires are ok and amp is ok.
4. Same CD, same track: thru the preamp to amp. Sound same as when CD player straight to amp?
a. you have two sets of outputs on that preamp, have you tried them both?
b. 4 inputs on the preamp, try each input, any difference?
btw, what AMP?