It could be the cartridge doesn't connect properly with the tonearm. I had the same problem with concorde pro's. I simply cleaned the contacts of the tonearm/cartridge and my problem was solved.

most carts in my experience have given a slightly stringer signal on one side, it stands out more on one side than the other, this is generally down to tracking forces of the spinning vinyl making the stylus have better contact on one side of the groove.

but yeah, if its a massive difference, clean your contacts, as well as remove the stylus and put it back to make sure its got good contact. clean the stylus with the brush supplied with it too

___________________
MUGGETS