That is almost never a good idea as it usually means a bigger ground loop, not a smaller one - that's what you are looking for to minimize hum from mains wiring......I have pluged each component to different wall socket....
That is almost never a good idea as it usually means a bigger ground loop, not a smaller one - that's what you are looking for to minimize hum from mains wiring.
You don't say anything else about your system, whether it is all recently purchased, unknown condition, untested with other gear etc, what source you have connected or if you just have open inputs. That makes it hard to identify any problem. However, you seem to be saying that the amplifier itself emits a hum noise when you connect the preamp. That suggests either or both the preamp and amplifier are wrongly (probably dangerously) earthed. Possibly, they have been messed with before?
check your power amp output noise without interconnects and then with interconnects and finally with the interconnects shorted together at the barrels.
These 6 measurements should show deficiencies in the power amp wiring.
If you measure output @ 0.0mVac for all six test arrangements, then the Power Amplifier has been wired to be tolerant to the way the interconnects are wired.
That means the wiring fault is inside the Source.
The line-out connectors from the tube preamplifier are not balanced for use with XLR connectors and I assume the input sockets on the CA100 amplifier have not been properly modified to accept a balanced input either, so what part of your system uses XLR connectors, which usually means a balanced line?
I guess the amplifier has been modified, since you say there are additional resistors between an XLR socket and original RCA input sockets on the amplifier but it would not make sense to change to a proper balanced 600 ohm line, just for the sake of it. I'm guessing XLR cables are for looks or for when the amplifier perhaps was used with another preamp. that did have balanced outputs.
Personally, I would remove the XLR adaptor wiring and use both units as designed, with RCA connectors. You probably wouldn't like to pay ($$$) for a transformer to adapt the PV10 to a real balanced line anyway.