When most people think of tube circuits, the first thing that comes to mind is often the use of high-voltage power supplies. It wasn’t a given for tube circuits, though, as a range of low-voltage devices were developed for applications such as car radios. It’s one of these, an ECH83 triode-heptode, which [mircemk] has taken as the basis of an audio preamplifier circuit.
This is a companion discussion topic for the original entry at https://hackaday.com/2023/11/17/a-low-voltage-tube-makes-for-a-handy-preamplifier/