Quad 405-1 Avondale

[AndrewGM]

I have recently acquired an Avondale modded 405 - 1.
MJ15003's and loads of other mods which have been beautifully done.

It hums quite a bit and read that earthing the input RCA's
directly to the chassis instead of just the ground bus between PS caps can silence a humming 405. I also read that relatively old PS caps can also be to blame.

It actually sounds great but the hum is niggling away at me.
Should I try all of the above ?
Can earthing the RCA's in this way cause further probs ?

I have only a CD player with fig 8 mains cable and passive 50 K stepped attenuator so I'm not suffering ground loop effects.

Thanks

And