I'm working on a preamp currently and using a motorized pot board. The board runs on essentially the same voltage as the filaments. It is a 6SN7 SRPP preamp with a B+ around 260-270V. In order to not exceed the heater to cathode voltage, I have to float the filaments. Not an issue. The issue is that the board is powered from the floated DC and connected to the signal ground leaving the entire ground plane for the preamp at 70V or so.
A) can I go to AC filaments, and elevate the center tap via two 100ohm resistors and then DC rectify to run the board after that using earth ground?
B) how much does the elevation of the heaters matter? Or a simple solution to slow the B+ until the heaters are up?
Like this maybe?
Thanks!
Blair
A) can I go to AC filaments, and elevate the center tap via two 100ohm resistors and then DC rectify to run the board after that using earth ground?
B) how much does the elevation of the heaters matter? Or a simple solution to slow the B+ until the heaters are up?
Like this maybe?
Thanks!
Blair
You have to use a separate transformer winding for the remote circuit if you want its ground to be separate from the filament supply ground.
How much does the heater-cathode voltage spec matter? About as much as any other breakdown spec, I suppose. If you violate the spec, you'll likely have arc-over between the cathode and the heater.
~Tom
How much does the heater-cathode voltage spec matter? About as much as any other breakdown spec, I suppose. If you violate the spec, you'll likely have arc-over between the cathode and the heater.
~Tom
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