Lyra Lydian Beta, Rega hum?

...and that's what I've told on my first post here...

David, i've never told that the hum is from the table. There shouldn't be any grounding problems with RB300 either except when there are some manufacturing deffects.

The first party to call should be Immedia to report a problem with the cartridge.

BTW do you connect this setup the first time or you used different cartridges prior?

The only thing that left for you to do is to contact Immedia and report that problem. It might be a problem with cartridge internal wiring.
BTW Rega turntable is a big compromise for Lyra but it shouldn't hum. Lyra can deliver much more from the Basis 1400. Basis 1400/RB300 combo will definitely smoke your current analogue setup.

...ain't rock-n-roll only in the world David, but for even listening to Metallica I would bet more on Basis1400.