Just to say that Russ bought both of these from me (at different times - the power amp had been on loan to Jake).

They worked together really well here with no hum beyond the minimum ear up to the speaker noise that's normal with valve amps. I had them running together in the study for a while with a Garrard 401, latterly with a Technics SL10 (into the phono input), an Arcam iBlink and a Sony ES CDP, into Tannoy DC6's - this was actually a stunning combo. I ran them both separately into the main rig as well driving the big Tannoys with no problems and the pre driving my Radford STA100 at the time. All no issues.

The pre-was driven north by Petrat and collected, so wasn't shipped - it would definitely have arrived undamaged. The Croft was shipped to Jake's (where it was fine for several weeks) and on to Russ. Prior to me getting it it was fettled by Alan (Firebottle) and sounded stunning here. Behaved fine for Jake too.

Unless something has damaged the power amp in transit (which I guess is possible) then this is most likely to be a local mains hum issue. @Russ can you show the layout? It's still most likely to be a ground loop in my view, though it's also possible that it or the attached interconnect is picking up transformer noise from something too close. The speaker flap is a bit odd though and looks a bit like DC.