I tried to write something about this project on an (American) forum but the 6T9 was "blurred" as it could be a sexual term. Crazy folks over there ...
The 6T9 was describes in the journal Nuts & Volts and the PCB was available from Spare Time Gizmo. Tubes are of a slightly different type, called compactron as they are wider that, for instance, noval tubes, have 11 pins and often much more is stuffed into the tubes. There are types with three triodes inside. The 6T9 (triode/pentode) and 6T10 (pentode/pentode) became very popular and if the prices were low ten years ago they are very high today IF the tubes can be found.
It's a simpel design with just one tube/channel, much like the 6BM8. But with tubes becoming unobtainable, better forget about this one.
I sold the board and all the tubes I had. Also, note some layouts for a four-tube amplifier, a push-pull design.