Galapac
1000+ Head-Fier
1) 5998 is a nice tube that I use exclusively as a power tube in my BHC although the GEC 6080 is nice too, I just prefer the 5998 a little more.
2) Try amazon or partsconnexion
https://www.partsconnexion.com/cgi-...d0a875b77f1157d6bb78322a865&search_field=Knob
2) Try amazon or partsconnexion
https://www.partsconnexion.com/cgi-...d0a875b77f1157d6bb78322a865&search_field=Knob