@thomaschan are you using the Lampizator with the 5670 and the AN DAC3 tube output with 6922/6DJ8? Both circuits are SRPP. Transconductance of the 6DJ8 is much higher. Also, the cathode resistor is bypassed with an electrolytic cap (220uF) in the AN SRPP. This will add gain. The Lampizator circuit has some local degenerative feedback without the bypass cap. I am not a fan of the 6DJ8. Too cold and analytical sounding.
Hardware: RPi Zero W | Allo Kali | ProtoDAC TDA1387 X8 | PGA2311 | Icepower 500ASP | Harbeth SHL5
Software: Moode 8.3.3
Source: Win 10 NAS
Software: Moode 8.3.3
Source: Win 10 NAS