Part 3: The Universal System (second section)

of The Vanderveen Project

Three forms of local feedback are possible with the screen grid of a power tube. The screen grid connected to the anode creates a triode. When the screen grid is connected to a tap on the primary winding, we have the ultra linear configuration. In the pentode mode the screen grid is connected to a constant voltage supply.

Local feedback is also possible directly at the cathode and the control grid. The cathode can be connected to an extra winding on the output transformer, or the control grid can get local feedback through resistors from the anode. These circuits belong to the super triode topology, as explained in the DIY-kits section.
The most important variations in tube amplifiers are discussed now, almost every amplifier will fit into this universal system. The next figure shows 20 examples of the many amplifiers that can be constructed with the universal POW80 and GIT80 transformers.

More news to follow soon!