Voltage Theory

The tattoo process requires power. While it is possible to run a
tattoo machine without a proper power supply (as in the actual
power supply device), it is not suggested. You could very easily
hook your tattoo machine up to some type of battery and it
would run. The proper power supply will allow you a level of
control over the primary energy that drives the coils. You can
control voltage with a typical tattoo machine power supply, while
some power supplies let you control more advance features.