So it sounds like one of my 4P1L tubes is not doing so good. I've been meaning to pick up some replacements but it looks like they're all in Russia. Any recommendations?
I get good service, but not fast delivery, from a number of old USSR sellers. I have used these more than once and would not hesitate to recommend them:
What year of manufacture is stamped on them? People claim the best of them are the early 60's vintage, and of the three sets i have the two early 60's pairs sound better to my ears. Its as though they have better extension on the high and low end of the spectrum.