Stereo channel balance/image

I just recently setup a rega p3 turntable with a cambridge 540p phono preamp on my system. I noticed that there is somewhat of a channel imbalance. The left speaker is just slightly weaker than the right speaker. I tested every possible thing , moving the speakers, swapping the wires, changing interconnects and i've come to the conclusion that it is not the amp. There's something definetely wrong with the turntable or the phono preamp it only seems to happen when I play vinyl. Strange thing is when I played Bob Dylan's "love and theft" lp, the stereo image seemed just right same thing for the "bringing it all back home" 180g lp... I also noticed that the right woofer is working and "thrumping" more than the left when the music is louder. Does any know why this is hapening? Any suggestions?