[planigan]

Ryan, there is another difference between the G and GT tubes. Most of the newer GT tubes have metal base and pin No. 1 is grounded. On some sets the pin No. 1 terminal may be used by the manufacturer as a common terminal for other circuits (other than the tube involved). If you use the GT tube you could ground out the circuit. This info was posted on Nostalgia Air, references, articles, Using GT tubes as substitutes for non-GT tubes. I also beleive the GT tube is a newer design of the G tube. Both class but the GT had the metal as opposed to the bakelyte/phenol/plastic base. I don't know what the designation was for the metal tubes but they where used do away with the metal tube shields. PL