I don't have a little dot, but i thought I would post here. Just got a XDuoo TA-02 which uses the 6J1 as stock, terrible tube. Also one failed after 30 mins of being plugged in (white cloud at the bottom, bass sounded awful).
So I decided to buy a pair of Mullard 5654 tubes off ebay. Got them today, put them in, and wow what a difference, brilliant body, the mids are a tad too warm sometimes, and the highs are a little less sparkly but the overall sound is much better. The are aged around 1964, Mitcham Factory, July, Week 4 (R4G4 code). Nice tubes, makes me want to try the Voshkod...
The TA-02 is a great little budget amp, for $112 retail it is incredible value, hybrid design.
Thanks for the guide. Using modded Grado SR-60's out of it at the moment.