Packed up the amp but before I did I tried the Svetlana 6H13Cs and a Fivre 12sn7 I purchased from another Head-Fier. I’ve tried the brown base before and found them ok but these black bases sounded fantastic. I noticed that the black base doesn’t look at all like the brown base. After a little google search I found them to be a Brimar 12sn7. Great synergy with cheap Russian power tubes and the Auteurs. Anyone know where I could buy more?