Does anyone ever retube Sonic Frontier preamp. SFL2?

If you mean biasing the tubes, the tubes in pre-amps do not need to be biased. Sonic Frontiers will sell you matched pairs for your pre-amp, but matching is different than biasing. I have re-tubed my SF Line 2 with matched pairs of tubes several times. Good Luck. Craig

There are two small bias trim pots next to each of the two banks of tubes; however, do not touch them unless you have a voltmeter and have the instructions from Sonic Frontiers that they will fax to you. If you order the matched sets from Sonic Frontiers, they will include a drawing of these trim pots and where you should set them for the tubes you are getting from them.

However, I understand that it is not critical, and you can just leave them alone. If you get tubes from another source, I would not touch them, unless you do the voltmeter procedures outlined by Sonic Frontiers.

When I asked Kevin of Upscale Audio, he said he has never touched them or adjusted them and the replacement tubes he has sold have worked fine.

I replaced the tubes as matched pairs and it worked OK. Of course, I had to roll tubes to lower the noise floor and obtain the preferred sonic flavor. Thanks for all of your help.

How you contacted Sonic Frontiers. They do have a procedure to accomplish biasing the new tubes. Put in some new old stock tubes like Mullard or Seimens "A" Frames, very nice. There are a lot of other good options to select.