I have had multiple issues with JJ preamp and power amp tubes causing my amp to cut out or stop making sounds at all, due to JJ's insistence on using thinner-than-standard contact pins on their tubes. Has anyone else experienced this? I'm in the market for matched sets 6L6GC's, as well as 5 12ax7's pre-amp tubes. I have no idea what or where to buy. Tube Amp Doctor? AmplifiedParts? Should I go for Mullards? Winged-C Svetlana? GrooveTubes? New? NOS? Any thoughts or recommendations for a Peavey 5150 combo?