I bought a set of Sovtek 6922 tubes from ARC two months ago and although they are reasonably decent, my ARC LS16 still doesn't sound as good as I would like. As more experienced tube users have suggested, my next step will be to try some NOS tubes, probably from Kevin Deal at http://upscaleaudio.com. If I'm still not satisfied, I'll sell the LS16 and not use a preamp at all!
