Hell yeah! I received my four NOS/NIB RCA 7199 today. These tubes are AMAZING. I really like Sylvania but this one is just incredible. The high freq extension is much, much better than the other 7199's I've tried. Vocals have more body and air and the bass/mid bass and dynamics is killer. I found myself listening at higher volumes with these tubes. I love them. I'm gonna stock up on them for a lifetime supply. All you Dynaco owners should give the RCA a try. You won't be dissapointed!