If you are sure its the cables, try wrapping some aluminum foil around them. If you still have the buzz, try grounding the foil to your preamp/phonostage/integrated. Not sure if it will work as I've never tried it but essentially you are creating a shield around the cables and attempting to drain EMF/RFI away from your cables.
The source of the buzz is likely a transformer in a power supply or the motor in your TT. An unshielded power cord can sometimes put off enough energy to cause the buzz too. Moving your cables and gear around to give a good distance from your cables might also help. Also, make sure that any small signal cables that must be located near a power cord don't run parallel to them if you can help it (try to keep an inch or two separation if not more). If they must cross each other, try to hold them to make it a perpendicular intersection.
Hope that helps. Phonostage noise can be really frustrating to eliminate.
