Got the kit version of ember about a month back and since been building and toying around with some mods(more for usability/transportability).
Manage to integrate the ODAC in the chassis and have move the led pot to the front for easy access.
Tubes I've got and tried so far are Electro-Harmonix 6922,6922 gold,12ax7,Shu Guang 12au7,RCA 12au7 cleartop and Voskhod 6n1p(the last 2 courtesy of jeremy).
Currently using the Shu Guang 12au7(my favorite and might be permanent) tube as I find it to be the least hiss/noise prone for my AKG K701 and Maddog with high gain,
low output impedance and with input caps bypass setting, also the scratching sound that you hear with other tubes when changing volume(when input caps are bypassed)
is not present with it. Very powerful amp indeed and overall I'm very happy with it and it really pairs well with my K701.
The front with the LED trimmer pots easily accessible
Back view with the ODAC underneath
The ember with it's partner K701