What’s the best tube for a Sonic Frontiers SFL-1 preamp

I run a Genalex, Gold Lion in mine,... fabulous! GL with yours @skipper320; it's a terrific linestage that paired with the right amp will bring you pure sonic joy. I've run mine with TAD, Hibachi Monoblocks, a Cary 808R tuber, and soon a Sugden Bijou (Class A) "AmpMaster". It's a wonderful piece

Mullard 6201 I believe is what I used to run when I had a SFL 1, but that was sometime ago. Very nice preamp with the right tube and for the money. Sold the SFL 1 and moved to a ModWright SWL 9.0 SE which I liked much better. I recall the Mullards were what everyone was using and UpScale Audio recommended too which is where I think I purchased from. I remember the Mullard was much better than the stock tube if that helps.

SFL 1 lean side of neutral so my favorite was Amperex / Phillip Holland.  

I just picked up a mint SFL-1 last night , had a "new"  Brimar NOS AT7 but when I set it up I was pretty disappointed....dark, compressed sound it was bad.  Put a new JJ ECC81 in tonight and it sounds great.  

I was actually looking for a pre for my brother but he doesn't want to deal with tubes so I couldn't pass on it for $500....     its built like a tank.  

It will see duty in a second system but for now I am really digging it