If you have a shared line, make sure all connections in the line (like wire nuts, outlet screws, any cut in the wires) are as tight as possible. They are source of added resistance that degrades audio performance. You might even consider using a
silver cream on the contacts. The line connection to the breaker and ground buss should already be very tight.
A dedicated line could be installed with thickest ga wire. This is why you install a 20A service for audio system outlet, instead of 15A; not because you will use 20A, but because you want the thicker wire to reduce resistance, especially when outlet is far from the service panel.
Because of these opportunities for variably higher resistance with wirenuts and outlet connections, cheap brass contacts in outlets, etc. you should make sure the audio system has a good ground. Ideally it would use a single 20A outlet, or 2 nearby 20s shared, so that there is only one ground path back to the breaker panel and all components in the system see the same ground resistance. A power strip makes this easier, but most strips add their own unacceptable levels of resistance, and audiophile quality strips are very expensive, so DIY your strip with thick wire and copper contact outlets like
Jena Labs. Remember the neutral is also ground. Earth wire is for safety, but neutral is the return for the single ended power and can just as easily create hum with bad connections when two different circuits power the system, the loop forms through the interconnect grounds.
When you can't fix the different ground resistances, like the above example of multiple circuits serving the system, or when when bringing grounded cable TV or FM antenna into the system, and you get a ground loop hum, use a cap or transformer to isolate the signal wire that creates a loop with the grounds. Lifting the earth wire with a groundbuster plug will often not work, because the neutral wire (return conductor for the single ended power) is also connected to the ground buss in the panel. Jenson Transformers makes good signal isolation products like this to stop hum. I use their Iso-Maxx on my FM antenna.
Groundbuster plug is a useful tool for diagnosing ground related hum, but it shouldn't be left installed in the system. Remove it immediately after diagnosis and fix the problem correctly so the safety earth is restored to prevent electrocution.
As for power conditioning, I like balanced power transformers because they offer a floating ground so all components see the same ground voltage to avoid voltage flowing in a loop, and it eliminates DC offset which causes power transformers to buzz. They also offer a reservoir of magnetic energy to improve transient current delivery to components whose power transformers are undersized, like most tube components. Of course as a huge inductor low pass filter, it filters out the HF noise from the mains. A large balanced transformer has its own mechanical vibration sound which small sorbothane footers will cure.
I also like
Purepower regenerator and
Brick Wall surge protectors.