Did you get the very comprehensive instruction booklet that explains how to adjust for best sound? If you need it, I can search for mine, and make a copy for you.
Never bright in my experience, with Shure, and Grado MM cartridges.
Is there any trouble with brightness listening to CD's through the linestage?
I have two non-bright, proper sounding units in storage, as I could not bear to part with a "classic" design, when I converted to tubes. Another is still being used by a family member.
The suggestions above seem to cover most possibilities.