OK I'm a dump shit with a strong preferences! :-)
That said, have you tried disconnecting the IC's from your TT (cartridge) to the phono stage? If not try that, leaving the IC's to the pre-amp in place and seeif that changes anything. The phono stage might be fine but the IC's from the TT/cartridge to the phono stage could be the ones picking up stray magnetic fields, as opposed to the IC's from the phono stage to the pre-amp.