Hi fellas! First post here for a new Valhalla 2 owner. Got my unit used and it came with some russian 6N6P and 6N1P tubes installed (not the stock ones). I'm totally new in the tube amp stuff, so please tell me if I'm wrong, but I think the tubes need replacing, cause I'm getting a distortion on higher volumes, which I didn't get on my old Magni 2 amp. Waited for the tubes to warm up (2-3 hours even), but the distortion doesn't go away. It's mainly present on low impedance headphones (DT770 32Ohm) and not that noticeable on high impedance ones (HD650). Again, no distortion whatsoever on either of these pairs of headphones on my Magni 2. So first question is - am I right by thinking the problem comes from the tubes and if yes, do I need to change both, or just the 6N1P pair? And now about tubes... from the little time going through some topics in different forums, searching for consensus about tubes that are liked by the majority of people who tried them, it seems that the JJ E88CC Gold Pins, or Genalex Gold Lion E88CC are some pretty decent options. I'm definitely planning to upgrade the russian ones that the unit came with, but am pretty low on budget, so getting a single decent pair would be enough for now. Here are some specific questions about the tubes in general: Do I need to change both 6N6P and 6N1P to hear a noticeable difference in sound, or swapping the 6N1P only would be enough? When buying a pair of tubes, is it necessary for them to be matched? Does gold pins make a huge difference compared to regular ones on a same model tubes? Is it advisable to buy NOS tubes, or it's better to find used ones? If used, what should I look for (how much time should they've been used at most)? Definitely subjective, but if you were able to buy a single pair of Input tubes (budget ones), which do you think work best with the Valhalla 2 and bring the best out of the HD650 and HD800S (planning on buying those in the future lol) Thanks for reading and hopefully someone will reply to this wall of text P.S. Anyone selling a decent cheap pair of tubes in Europe? Bit broke atm, but would try to save up some funds for a buy.