It's just so they comply with a standard tube base pattern. Back in the day there would have been 20 different tubes that used the same socket, with different pinouts.I am working on my XXX but I took the back off my 6505 and these tubes also have one pin pulled. What is the purpose of this? Tomorrow I’ll look into getting a multimeter to adjust the Amp bias.
Absolutely NOT.I come to understand any tube will work as long as it fits into place.
Four completely different tubes.What about 6V6, EL84, KT88, 5Y3?