I need to buy an outboard preamp so I can get rid of that phono cable extender. It’s horrible. I’m surprised so many people have recommended to just extend it. The hum is so bad it’s not even listenable. Rega seemed adamant that it’s a certain length for a reason.
The reason people recommended trying an extension cable is that in most situations it would not cause anything like the hum problem you experienced. I think someone mentioned early in one of your other threads that the Rega’s grounding configuration is unusual, which presumably has contributed to or caused the problem in this case.
In any event, congratulations on finding a solution to the rumble issue. I can’t comment on phono stage possibilities in the price range you are considering, or how they might compare to the one that is built into the AV7704. I note, though, that the Atoll phono stage provides a choice of two load capacitance settings, differing by 100 pf, which is nice although not quite as flexible as the four or so settings some much more expensive phono stages provide.
FYI, BTW, whenever any phono stage provides a load capacitance setting designated as "0," the actual capacitance presented by that setting is not really zero (which would be impossible). My guess is that it may be a few tens of pf’s, and the 100 pf setting is 100 pf higher than whatever it is in the 0 setting.
Continued good luck. Regards,
-- Al