Welcome to Issue One
The Tube CAD Journal is a monthly online magazine devoted to tube audio circuit design. Each month we will present some fresh looks at some old tube circuits and some altogether fresh tube circuits as well (yes, new tube circuits are possible). Circuits and more circuits. While we plan on covering complex tube circuits, like phono preamps or power amplifiers, our focus will be primarily on elemental circuits. Elemental circuits are the primary topologies, part configurations, arrangements that can stand on their own as recognizable functional circuits although they may be part of a larger circuit. A power amplifier circuit, such as the famous Williamson, comprises several sub-circuits: the Grounded Cathode amplifier, the Split-Load phase splitter, and the Differential amplifier, and finally, push-pull output stage. Just as we must understand how a resistor or a capacitor function in a simple circuit, we must understand the function and logic of these elemental circuits before we can understand more complex compound circuits.
As these atomic circuits are like archetypal roles, mustached villain, white hatted hero, crusty, but actually soft-hearted boss, which can appear in many types of movies: western, mystery, sci-fi, each of these circuits finds application in infinite varied circuits: microphone preamps, SE amplifier, electronic crossovers, audio expanders and compressors, headphone amplifiers, and so on....
Armed with knowledge, the tube hobbyist can move beyond just being a mere part exchanger. Of course, part quality is of extreme importance to any quality audio design and part upgrading is an extremely cost effective way to upgrade a stereo system, but do not forget that the parts are only there because someone understood the structure and the logic of the circuit first. How sad and comical it is to see an audiophile, who equipped with a soldering iron and a platinum credit card, changes the resistor that feeds the LED on the front panel with a ten dollar bulk foil resistor in the hope of dramatically improving the sound of his system. Or the tube expert who can talk for hours on the superiority of one tube brand over another, but hasn't a clue