12x7 tubes

having had the black ice/jolida dac (in chris johnson upgraded form), i would agree with the op in wanting a warmer smoother tube in its output stage

that said, i would add that that particular unit benefits greatly from bypassing the front panel volume control for improved sound quality... (if it is not needed for the headphone amp function, of course)

 I was in checking tubes out on BJ’s website and saw he had Ge/ Kentucky Radio pewter plates in stock.  You might want to inquire on those.  A little more cost than the Tungsram and Ge long gray plates.  They are exceptional ...as good as RCA black plates.  Probably the best Ge 12ax7.

Just order a pair of Tungsram 12x7 from Brent Jessee website. I will let you know how they sound with my system.

Add my vote for Brent Jesse. I have almost no tube knowledge and have made several purchases from him based on his advice. It has always been an improvement to my system and he is a pleasure to work with.

+1 Brent Jesse,patiently helped me upgrade tubes in my Herron phono and LTA MicroZotl….