Hi Paul: NOS means "new old stock" old tubes that have not been used. they are not intrinsically superior in all cases. there are crappy NOS tubes and good new production tubes, but many people like tubes from the 50's and 60's better. I have found this to be my experience. The term is "rolled tubes" when one rolls tubes, they are simply swapping the existing tube with a compatible replacement and experimenting with the sonic signiture of their equipment. I am not very technically adept, but single ended means one tube produces the entire sound wave while push pull means one tube produces one half while another produces the other half. SET's are considered more "linear" whilst PP setups can produce more power.
NOS, single ended, push-pull???
I am not sure what the following terms mean: what are NOS tubes? I see the term NOS often, it seams to imply to me that these tubes are superior. single ended and push-pull? Also, are all tube amps class A? What does the term "roled tubes" mean? Thanks for your enlightenment. Paul