Guys, I know there's a few forum threads on this topic out there, but none of them quite answers my question. I want to try out a few different types of tubes to replace the standard 6922 tube inside my Rode K2. Do I need to replace this tube with the same type (i.e. 6922 aka ECC88) or can I use different types as well? I would assume that the replacement tube should have a gain factor similar to the default tube. Is this correct? Here's a list of common preamp tubes and their gain factors: 12AX7 / ECC83: 100 12AT7 / ECC81: 60 12AY7 / 6072: 45 6922 / ECC88: 33 12AU7 / ECC82: 19 From looking at this list, I would assume that I should be able to replace the K2 tube with either 12AY7 or 12AU7. Is this recommended? Also, I found out that the famous Neumann U47 and their clones (e.g. Lawson L47) use EF86 tube types. I don't know their gain factor. Would I be able to use this type in my K2? I hope somebody can give me an answer...thanks!