New tubes for SFL-1 / SFS40

I'm thinking of replacing some tubes for both my amp / preamp. Currently, the system doesn't sound "tubey."
I heard the nature of SFL-1 isn't very tubey...but I am
hoping that replacing some tubes on both pre/poweramp will
give me the "tubey" sound that I'm looking for.
Please give me some suggestions on the tubes.

Thank you very much!

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.

Which pre-amp do you need tube suggestions for, a Sonic Frontiers SFL-1 ( or a Line 1 ( 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.
You won't be able to "ruin" the sound of SF amps just with changing tubes! You have to change complete design, and that means to find some other brand of amp that suit your taste. Try older CJ?
Try Mullard or Philips Mini Watt 6922's for a "tuby" sound (these are the ones). Too many fake and/or legally rebranded Amperex's out there (the namesake was sold) if you do not know how to ID them. Also (unless your'e feeling lucky) avoid Mullards/Philips being sold by a dealer in Hong Kong on Ebay (his seller ID contains the name of a brass instrument). Per feedback on the web some of the stock is authentic and some is not (much written on the subject).

If your amp uses 6550 or KT88 output tubes, then I agree with ElDragon in that you might be better off with a different design (given your stated goals), but a few 6922's in key positions are also worth a try, IMO, and should not cost that much. First find out what positions are more crucial to changing the tone of the preamp (perhaps just two new tubes will do the trick instead of changing all of the 6922's).

If you can sit tight for a while reviews of the new EI Elite 6dj8 tubes (a type of 6922) should start showing up @ I don't know what vintage tube/brand they copied in the design, but their current EL84 tube is a very good copy of the vintage Amperex version ($40 a matched quad Vs $300-$400 for the real thing from a NOS tube dealer:-).
Thank you for all your responses.
To clarify, I have SFL-1, not Line 1.

Dekay, do you know where I can purchase EI Elite 6dj8?
I am thinking of trying them out.

Many of you suggested that I change my system. I think you are right but before I do that, I like to try some new tubes. I am purchasing a ZERO Autoformer for my system...I am hoping that will make my system sound more "warmth".

Thanks again.

Hi Sean:

This is the only source that I have, though there should be others.

Prices are in BPS, so maybe 1.5/$US (haven't checked lately). Includes VAT and shipping is cheap.

I will probably try them eventually along with the 12ax7/12at7's.
Looked it up and now understand the 6DJ8s are for the amp, not the pre. My mistake.

A synopsis of the characteristics of a variety of 6DJ8 tubes is located on the Audio Asylum at Maybe that will help narrow down what tube will do the trick.
Hi Sean,
I know that you wanted to change tubes to get the 'tube' sound, but you may also get a lot of that type of sound by changing the coupling caps. Their are 2 pairs of caps to consider in the SFL-1, and a quad set in the SFS-40. Paper and oil caps may be the ticket for you.
Have fun!
Wow...this is getting interesting.

Dekay & Fpeel, thanks for the link.

Dtails, where can I find more information on caps? DIY? I'll do some research on AA. Thanks alot. This is fun.
No problem, do a search on 'paper and oil caps' should bring up places like The Parts Connexion, Audio Asylum. The Parts Connexion has them for sure
Let the fun begin!
I just purchased a Zero Autoformer. My system sounds more dynamic (much better bass) and the high is more focus.
Because of the extended mid-bass, my system sounds more warmth overall.
I just purchased 4 6dj8 Globe Amperex from Ebay.
As soon as I get them installed, I will give you an update.
But the new Zero really helps my system.

My system doesn't sound dry and bright like before.