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 ...

[Jenny List] shows us the way with her neat headphone amp build. The build starts with an off-the-shelf preamp kit based around two common 6J1 tubes. These Chinese pentode valves come cheap and ...