Does RMS / duty cycle equivalency matter...

[veeblefetzer eddy]

. . . when running filaments on DC? In the case of a 12AX7 w/ 6V parallel filaments, should they be fed .707 x 6 (4.2) volts? Or does the resistance difference between cold and hot states make the duty cycle irrelevant? Does the rest period during the cycle swing make any meaningful difference in wear & tear on red-hot tungsten?

 

[rayma]

The 6.3 VAC rating is for RMS voltage, which is heating equivalent to the same DC voltage.
For tube filaments, 6.3 VAC = 6.3 VDC.

 

[veeblefetzer eddy]

A handy thing for me to know forever. Danke schön very much for the quick response. Now I can proceed with the bits I already have.

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