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.

The Wurlitzer 206 is the student version of the Wurlitzer 200. It is equivalent to the 200 in every day, but it is mounted on a cabinet instead of legs and some features of the amplifier are disabled. However, all of the components that are in a 200 are also present on the circuit board of the 206. Enabling vibrato and the aux output is therefore as simple as adding some wires and a 10k potentiometer. Here is how we do it.

Carbon composition resistors are those brown cylindrical resistors that you’ll see in most amps made before 1970. All resistors produce Johnson (thermal) noise, a byproduct of the fact that resistors dissipate heat. However, depending in their material composition and shape, resistors may produce other types of noise as well. Carbon composition resistors produce the most noise. But is this really a bad thing? Yes and no.