New tubes for SFL-1 / SFS40

New tubes will change the sound but maybe not as you like. You should try changing your gain tubes first with NOS telefunken or mullards and see if that is going the right direction. Many times you will get better sound with these than new tubes. If that works, then spend the real money on NOS output tubes. It's a lot easier to spend $75 for a pair of 12ax7s than $300 on EL34s and realize it didn't help.
If you get some well used/almost dead older telefunkens, you may get to experience the real tubey sound you thought you were looking for. After about an hour you will realize that that is a "microphonic" almost echo that is just too much.
Good Luck

Talk with Kevin at Upscale Audio.

He know the SF products.

I actually called Kevin at Upscale Audio but he wouldn't sale me any 6dj8/6922 tubes because I didn't buy my amp/pre-amp from him. :( darn it.

Seanchau,

Which pre-amp do you need tube suggestions for, a Sonic Frontiers SFL-1 (http://www.anthemav.com/pics/sfl1big.jpg) or a Line 1 (http://www.anthemav.com/pics/line1big.jpg)? These are two very different products. Your most recent reference to 6922s suggests a Line 1 which takes six 6922s. Your original post referenced the SFL-1 which uses a single 12AT7. Which is it?

BTW, along with a wide variety of other tubes Upscale *does* sell replacement 6922s to the general public. In fact, they stock a couple of different Russian tubes, the modern Sovtek 6922 and a NOS 6H23. Upscale also has some NOS 6922s which they keep in reserve for customers that bought hardware from them. Just a little clarification.