- The cathode
- The Anode
- The Grid
This is the first post in our series on Tubes vs. Transistors. I'll do my best to keep this fun, informative, not uber technical and to the point so we can all have something to look forward to each day. You may have heard the term "Audion" as there is a UK manufacturer using the name to build tube electronics as well a popular MAC MP3 player software leveraging the name as well. The true origins of the name refer to the first tube amplifier invented by Lee De Forest in 1907. Until the invention of the Audion there was no such thing as an electronic amplifier. De Forest's invention was not an audio amplifier but rather a radio amplifier - but it started something big for audio. In the early 1900's radio, then known as "wireless", was listened to on crystal radios - basically a piece of crystal with a tiny wire touching the crystal surface and both crystal and wire connected to a set of headphones. De Forest was looking for a way around using crystals - playing with heating a gas tomimicthe action of the crystal - a well known but unexplained phenomena at the time. To take advantage of the heated gas's tendency to conduct electricity, he captured some of the gas in a glass envelope called a tube. Around the glass tube he wrapped some wire and to that wire he attached a set of headphones - he heard radio. In later experiments he discovered that if he placed a small piece of wire inside the glass tube, formed in a grid pattern, the radio reception was improved. He now had a wire at each end of the glass tube and one in the middle. De Forest had stumbled onto what is known as a Triode: meaning it has 3 parts. While DeForest's triode worked better than any crystal radio receiver of the time it was not a linear audio amplifier - it was a non-linear radio receiver. DeForest had incorrectly determined that the glass tube had to be filled with gas in order to work - which was the entire basis of his thought. In fact, so convinced was he of this fact the patent he took out specified the gas requirement and the name "Audion" came two words: Audio and Ion (as in ionized gas). Turns out he was dead wrong. It wasn't until 1912 that Irving Langmuir of General Electric figured out the Audion could become a linear audio amplifier by removing all the gas DeForest had so adamantly demanded be included. Once the gas and the air had been removed from the glass tube what was left, of course, was a whole lot of nothing called a vacuum and to this day, most of the world refers to this type of amplification device as a "Vacuum Tube". Our UK friends refer to it as a valve, which I'll explain next. A triode vacuum tube is the most common of all tubes, even today. If you listen to tubes in your high-end system, chances are quite high you're listening to a triode. Triode means three and the three elements in a triode are:
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