All tubes follow the same basic principles. Inside a tube’s glass enclosure, you have 1) a vacuum and 2) at least two electrodes (but often more, depending on what type of tube we’re talking about). Each electrode has a specific job: either releasing electrons, attracting electrons, or slowing down or speeding up the flow of electrons. We’ll talk about these jobs later. For now, the main thing that tubes are intended to direct electrical current from A to B in some way that is useful to the circuit.

All Wurlitzer electronic pianos - from the model 112 to the Wurlitzer 200a - are more or less built the same. There are subtle differences in the mechanical action and the amplifier, but they all follow the same basic principles.

When you hit a key on the Wurlitzer electronic piano, a felt-tipped hammer rises and strikes a metal reed. The reed vibrates to a certain pitch, which is determined by the weight of a lump of solder at the end of the reed. A pickup converts the vibration into an electrical signal, which is finally amplified by the onboard amp and sent to a speaker.

Here’s how it works in a little more detail: