Interesting. Hum can be a problem with transformers - I have that very challenge myself at the moment since fitting the Jelco arm, as the interconnects Dave supplies, whilst sounding excellent, do seem to be hum magnets, but that'll be fixed when I visit him shortly. Hum wasn't a problem before when I had the Techy arm and the same cartridge and transformer.

Correct positioning, and eliminating earth loops seems to be the key with transformers. Get that right and generally there's no problem.

I've not heard the Phono2 so can't comment but I've tried loads of other active MC phono stages, some pretty expensive ones, with the 103 and none of them come close to emulating the performance I get with the A23 through the Croft's valve MM stage. Perhaps results are different through a valve phono stage? Since you're thinking about building a valve amp, why not build one with an all-valve MM phono stage and revisit the transformer thing to see what happens?

I'd be curious to know your thoughts and would willingly lend you my A23 for trial purposes

There's so much to learn with this hi-fi malarkey!

Marco.