The 6J1 seems to be ubiquitous throughout the Chinese kits, which is surprising when you understand that it’s not an audio tube at all. Instead it’s a small-signal VHF amplifier, a rough ...

There are a small handful of old tubes that need an impressively low voltage to work, though, and [J.G.] has put a few of them to work in this battery-powered audio tube amplifier. The key to the ...

Uniquely, Dynaco sold its amplifiers in two different ways: preassembled or as DIY kits (called ... options to tube roll to ...