All tube amps that I have worked on have unregulated power supplies. This type of power supply is relatively simple, and very inexpensive to build. In this article, I'll discuss the major parts of an unregulated power supply and how they fit together to provide enough power for the typical tube amp. Tube amp power supplies must convert this AC to DC and step the voltage up to somewhere between 400 and 600 volts and occasionally even higher. Transformers are used to step the voltage up or down.
Transformers consist of a core with two different strands of wire wrapped around it.
One strand is the input and the other is the output. The number of windings of each strand determines the ratio of input to output voltage. For example, if there were equal windings on each side, the voltage would be the same going in as coming out. It is very important to correctly set the input voltage switch. Alternatively, if you have 110 volts at the wall and have the amp set for 220, then you will only have half the voltage that you want.