You can plug them in anywhere actually, they don't so much interact with your equipment as much as your person, i.e: yourself.
I have owned a pair of them for several years...
The effect they have is not at all subtle if set to 12 o'clock or above.
They operate in essentially the same manner as the Acoustic Revive RR-77 and other devices tuned to generate the 'Schumann resonance', except that they offer a fully adjustable antenna and intensity control.
