replaced the old 6l6b sylvaina original 1957 model stromberg/carlson PA amp used for guitar,these tubes tested even and veryhigh output on hickock tester,great sounding and strong low to high notes,real dynamic responce,ive never heard my les paul this dynamic,dont worry they burn a little blue (slight impuritys in vacume causes that,not a problem,4 rated but im not sure about distortion,it has a killer voodoo child e chord,great sounding tubes!

I put a set of these in my Fender Hot Rod Deluxe when my amp tech did some mods. He checked these out and said they were made on American machinery to the same specs and design as the old black plate RCA tubes that in my opinion were some of the best guitar tubes ever made. (of course I'm old school country, rock, and blues player) so you may or may not agree. These tubes sound fantastic, are very warm, articulate and dynamic with clear clean tones and just the right amount break up as you turn up.