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Saturday, July 10, 2021

Tube of the Month : The 416D


After last months post about the 6EN4, let's continue with another rather uncommon tube this month. I present to you the 416D.

The 416D is a planar triode developed by Western Electric for very high frequency applications in the range of several GHz.

The 416D does not come in the common glass bulb but is housed in a shell composed of ceramic and metal. The metal parts of the housing also serve as connections to electrodes. There are 4 versions from 416A to 416D. The tube is an indirectly heated triode. It has a 6.3V heater which consumes 1.85A. The Western Electric data sheet of the 416B lists an amplification factor of 200 coupled with a transconductance of 50.000 micromhos. A candidate for a phono stage maybe if you dare to cope with the unusual base and shape and need to connect to the shell. I have never seen any suitable socket and connection accessories for this tube so you probably would have to make your own. But could be worth a try and I heard from some DIYers that they used this tube for auto applications.

The pin extending from the top connects to the plate. The upper metal ring is the grid connection and the major part  of the housing connects to the cathode which also connects to a base pin. The heater is powered through two of the base pins.

The datasheets I found do not show any plate curves, so I cooked up an adaptor to use it in an octal socket on the tube tracer. Here are the plate curves which have been taken using 0.5V steps on the grid.

Not exactly a linear tube but linearity is not of importance in high frequency applications. 

The 416D I have came wrapped in padding material packed in plain white boxes.

What an interesting tube. If you have used this and have some experience with it, please let me know.

Best regards


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