The recent thread on running tubes at lower than normal HV got me wondering about the use of an 8BN8 triode/dual diode tube in the popular Drake 2B receiver. The 8BN8 is specified to use an 8.4V filament supply and the 2B filament circuit is nominally 6.3V. There is such a thing as a 6BN8 tube. I'm guessing that the people at Drake got a good deal on a lot of cheap 8BN8 tubes and that's why they used it. I would bet that it is the tube with the longest life in those rigs.