I'd start by checking your interconnects are making good contact with the connectors on the TT and preamp (swap them out if you have spares), also check that the TT ground connector is securely connected to the preamp.
If the hum is still there then search up 'Ground Loops', it may be worth experimenting with ganging up all the mains plugs to a single wall socket if you haven't done that already.
Other than that I'd try to locate the source of the hum by disconnecting equipment until the hum goes away. Also check to see whether you have any equipment nearby that may be emitting interference.
The TT and preamp you reference look pretty high quality and I would not expect to hear any hum at all. The link provided by @hagtech looks like a good starting point.
If the hum is still there then search up 'Ground Loops', it may be worth experimenting with ganging up all the mains plugs to a single wall socket if you haven't done that already.
Other than that I'd try to locate the source of the hum by disconnecting equipment until the hum goes away. Also check to see whether you have any equipment nearby that may be emitting interference.
The TT and preamp you reference look pretty high quality and I would not expect to hear any hum at all. The link provided by @hagtech looks like a good starting point.