The Yellow Jacket socket is supposed to limit screen current and correct the bias circumstances for the el84 tube. I'm not sure how "universal" this could be to any amp they may be used in since amps vary considerably. One concern I might have is that there's no indication that plate voltage is adjusted. And el84's have a max 300Vp. A typical Vibro Champ has a plate voltage of 420+!!! That said, the limitation of screen current may be sufficient to keep the el84 alive.?. I know that some guys have used these in their Marshall amps. And many Marshall amps have over 400Vp. So these would be my concerns. I'd want to know more about what's inside that converter socket so I could equate the changes to real world circuit analysis before putting my stamp on using them.