Posted on Feb 7, 2014

Vacuum tubes represent an electronic technology whose roots extend a century and more into the past. With the exception of their continued use in certain niche applications, they have all but vanished from contemporary electronics, having been replaced by an endless array of solid state switching, amplification, and display technologies. Yet, despite all of this, it

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seems that interest in vacuum tubes and the "hollow state" technology that makes them work refuses to die. I`ve done a fair bit of tinkering with vacuum tubes, even to the extent of building a few of my own. I actually wrote a book about it. This article, however, comes from a different vantage point. In essence, I`ve identified a piece of contemporary electronic junk that, while not intended to be a vacuum tube in the classic sense, shares the necessary features of radio tubes. It can be induced to amplify feeble audio signals from primitive radio gear like crystal radio sets. Such experimentation is a lot of fun, and the end result is actually useful. That said, let us not overlook the fact that most vacuum tube experiments, including the ones to follow, involve the use of high voltages. Besides the obvious dangers associated with electric shock, miswired batteries can overheat and short circuits can produce fire. My presumption is that the reader is familiar with basic electrical principles, competent with regard to safe practices, and endowed with some level of common sense. Remember, you are responsible for your own safety. Before I describe what I`ve been playing with, it is worthwhile to engage in a quick review of what makes a classic vacuum tube what it is. It would actually take volumes to discuss this in a comprehensive manner, but let`s summarize things this way. We start with a common light bulb, that is, a...

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