Try this if you haven't already:
Use 1 AC wall outlet receptacle for your entire system with the possible exception of your device with the wall wart ac plug. Just use a competent AC Strip.
Next float the ground of your power amp and phono stage (use a cheater plug). The goal is to have your preamp as the only piece with a grounded AC plug.
Initially you can use a turntable ground wire. Turn everything on and give it a try. If the HUM is still present then unground the turntable and try again. Should work unless as mentioned previously your phono cartridge and TT are angry with each other.
Good luck!
Use 1 AC wall outlet receptacle for your entire system with the possible exception of your device with the wall wart ac plug. Just use a competent AC Strip.
Next float the ground of your power amp and phono stage (use a cheater plug). The goal is to have your preamp as the only piece with a grounded AC plug.
Initially you can use a turntable ground wire. Turn everything on and give it a try. If the HUM is still present then unground the turntable and try again. Should work unless as mentioned previously your phono cartridge and TT are angry with each other.
Good luck!