07-26-2013, 09:19 PM
6D6 and 78 are very similar. Interelectrode capacitances are slightly different because 78 has an internal shield surrounding the plate while 6D6 does not which makes it require an external shield.
6D6 was an RCA design based on the 2.5V 58 tube, while the 78 was a competing Sylvania design.
They can easily be interchanged, but you may have to realign the tuned circuits because of the different capacitances.
6D6 was an RCA design based on the 2.5V 58 tube, while the 78 was a competing Sylvania design.
They can easily be interchanged, but you may have to realign the tuned circuits because of the different capacitances.
