Grounding Question for floated filaments

[Blair]

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?



Maybe like this??

Thanks!

Blair

[Brik]

Hi Blair,

if I am not mistaken, you are rectifying the direct current voltage source (1/4 B+) with a 4.3V P-P ripple, ending up with 1/4 B+ to the Remote Circuit.

Brik

[Blair]

Yeah,

Big goof on my part. I need to figure out how to install another cable to pipe my DC to my remote circuit.

Thanks!

Blair

[Geek]

No different than a Rogue Audio heater lift. They lift them about 100V.

Cheers!

[Blair]

Hi Gregg,

The question is whether or not the center tap can be lifted, and the DC rectified voltage can be grounded at earth ground? Is that OK?

Thanks!

Blair

[Geek]

No, you don't want to do this... put the B+ lift where you show the ground symbol.... like this: