Weak tubes on the right side of the pre-amp. Try sitching those tubes with tubes on the left side and see if anything happens, or if you've got'em, plug in some spares on the right side and see if anything changes.
If you haven't changed your set up at all since you put in the new pre-amp it shouldn't be much different. Try some other recordings and try a mono source like you can get from a tuner (normally there is a mono switch) or a test/set set up recording.
If you haven't changed your set up at all since you put in the new pre-amp it shouldn't be much different. Try some other recordings and try a mono source like you can get from a tuner (normally there is a mono switch) or a test/set set up recording.