A VTL amp sounds great with a pair of Brimar 12AT7 black plate with the copper posts a NOS tube. I use them in a VTL 125 mono block amp and like it very much. I use EL 34 tubes in My amp but just tried KT77 tubes and like it a lot I have no experience with 6550 tubes or KT88 tubes try it you may like it ? Marc
