Audio Reseach ref 1 tubes.

Is there any way to improve a Ref1 by changing tubes in the preamp?
If yes which on do you suggest?
Originally there are 8 6922 russian .
Yes there is. I am using Sovtek 6922s made in the 1970s from Kevin at Upscale Audio WITHOUT the ARC damping rings.
I have the 6922s from Kevin as well in a LS-25. Highly recommended for the $$. There are a lot of other NOS tubes that are pricey (especially needing 8), but they all have a characteristic sound. Which way do you want your system to change??
j k, could you describe the differences in the LS-25 you experienced with these NOS tubes? I would like to try these with my LS-25 as well. I saw that Kevin has several models available on his site. Do you know which would offer a more harmonically rich sound with less treble detail than the factory tubes provided, as my Von Schweikert VR-6's are a bit much in the treble. Thanks very much for your suggestions. Also would you suggest replacing the output tubes to the same in my VT-100 Mk II? Thanks again.
The experience with my LS-25 was a much more detailed mids, the same amount of treble but more beautiful and more delicately presented, more air and space in the music; mid bass is more defined, more holographic, male singers came to life; Lowest octaves of bass appear to be more powerful.
In general, the tubes are much easier to listen to than the stockers.... The thing I liked the most was it took a harsh edge and some siblance off of my treble, and the harmonics were better. Don't use the ARC tube rings with the 6H23 (NOS Sovtek 6922 from upscale). I also did my VT-100 -- More of the same good for the sound, not recommended if you do not know how to do the VT-100 complete alignment procedure. E-Mail me for more detail on the alignment procedure. I can't give you the procedure, but I can tell you how to get it and what it entails.