In the context of a power outlet, the term "phase" refers to the specific alternating current (AC) waveform that is provided by the electrical utility. In many countries, the electrical power grid delivers AC power with multiple phases, commonly known as single-phase or three-phase power.
It's important to note that in residential settings, power outlets typically provide single-phase power. However, in certain cases, such as in larger homes or buildings with specialized power requirements, three-phase power may be available at specific outlets or for specific appliances.
In audio, we use the normal single-phase outlet.
To keep interferences between audio components to a minimum it is sometimes recommended to phase out the system. You can do this pretty easily yourself.
1. Start with your power outlet or power bar and determine where the phase is.
For that, you can use a simple phase tester like this:
Mark the side of the pin that has the phase output.
2. On your device, you can use a phase detector like this, or measure it with a standard multimeter.
To determine the proper phase in this scenario, follow these steps:
Prepare the necessary equipment: a multimeter, a grounded outlet, and a non-grounded mains outlet (or use a cheater plug).
Ensure all components, including interlinks, are disconnected from each other and from the power source.
Connect one component to the non-grounded outlet, keeping it separate from the other components.
Measure the voltage between the earth connection of the grounded outlet and the chassis of the component being measured.
Reverse the Schuko connector (plug) and perform another voltage measurement using the same setup.
Compare the voltage readings obtained in steps 4 and 5.
The measurement with the lowest voltage indicates the proper phase.
3. After that connect the power plug to the phase side corresponding with your outlet or power strip and you're done!
Some people claim that this also can have audible benefits, but that is something you just need to try for yourself. Every room, system, and ears are different.
Have fun listening!