RCA Grounding Question

I once had unacceptable hum/noise when the input sockets were grounded on the chassis. Since then, I've always isolated the input sockets and run the input socket ground to the PCB and then from there a ground wire from the PCB quiet earth to the common earth point.
Series resistors in the ground lead would also help.

Thanks.. Yah, all my grounding is going back to the main system ground, just in case I want to use a ground lift circuit at some point.
 
The idea of the resistor in a ground wire is to make the current flow somewhere else, as it likes to takes the way of least resistance, so the "bad" noise stays away.
It can only be used in low current ground wires. The input of a power amp should only carry some voltage and very minimal current, so the 10-100 Ohms in the ground line do not really matter compared to the maybe 20-47kOhm of the hot input side. These are last resort tricks you may try if a usual ground concept does not work for your build.

Make a sketch of your grounding points and lines, sometimes that way you realize where a loop is formed.

Also keep an eye on induced hum, it may enter even a shielded wire at some position you do not except at all, not only near a transformer or mains wire.
A very little change in routing may make the difference.

This chip amp can be totally quiet, it is not to blame for any hum.