I got tired of going thru 6sc7 pre-amp tubes,after replaceing the tube sockets,making sure everything was soldered properly,changing caps,useing tung-sol glass 6sc7 tubes.I had the amp changed to use 6sl7 tubes.The amp is now more quiet,sounds a bit more responsive.What is everyone expirence with 6sl7 tube.Im looking to get a backup set or two.What are everone thoughts on tung sol,rca,ect. onthese tubes?