I recently had my MFA M200 monos serviced and retubed with matched 6550 wing C's from RAM labs. The tubes have a couple of hundred hours now and are rock solid stable. The MFA's sound better than I have ever heard them before with other tubes (KT90, KT88, 6550A and 6550B). I was going to sell them but I think that I will keep them even though I have other newer amps both tubbed and solid state. Thank you Roger for providing such good quality tubes. I also have retubbed my CAT JL-2 Sig MKII with your tubes and look forward to listening to it!
