Pan?
Are you saying that when you pan hard left or right, you get additional noise?
Seems a little odd, I have no similar problems with my eurorack.
Or are you talking about the trim pots?
If you turn them right up, there will be some noise, but I suggest that your input signal is too low if the noise is unbearable. What is the sound source? My soundblaster s/c is particularly noisy.
Good luck,
matt