That will entirely depend on your tattoo machine and your individual preferences. Wireless
tattoo machines usually come with their own battery pack as a power supply, or you can use a wireless
battery pack to adapt a wired machine. Most wired rotary and coil tattoo machines will use a standard power
supply that plugs into the wall.
You should consider the voltage range, the increments with which you can adjust voltage, whether it has a
timer or jumpstart function, how many machines can be connected simultaneously, whether it has presets, its
electronic protection systems, and of course cost.