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I started building my 4P1L kit today. I notice there is some "Fil Bias" circuitry on the SE Line Stage Power Supply board. Is this filament bias feature used for the 4P1L project?I've got the Rod Coleman document "FilamentBias_Supply" and notice he recommends a -9v bias for the 4P1L -- it looks like that is implemented via the Coleman Regulators by adding more voltage headroom. And I see that there are filament bias resistors, etc. on the main 4P1L Linestage boards. But I'm confused as to how this "Fil Bias" circuitry fits in, if it does.
Edits: 04/02/16Follow Ups:
The fil bias pad isn't used for a directly heated filament.
The filament is the cathode, so the value of the cathode resistor and the B+ voltage determine the cathode voltage (and the cathode current). I haven't read that particular document, so I don't know specifically what Rod is referring to, but with the values of B+ and cathode resistor I have used, I get a cathode voltage of about 8V-9V, positive relative to ground.
Kevin Carter
K&K Audio
www.kandkaudio.com
Thanks, Kevin.//The fil bias pad isn't used for a directly heated filament.//
Ok, makes sense.
What is C2 doing?
//The filament is the cathode, so the value of the cathode resistor and the B+ voltage determine the cathode voltage (and the cathode current). I haven't read that particular document, so I don't know specifically what Rod is referring to, but with the values of B+ and cathode resistor I have used, I get a cathode voltage of about 8V-9V, positive relative to ground.//
Which is exactly what Rod shows in his diagram in that document. Similar cathode resistor values too... But the -9V bias he mentions is confusing. It's just for my intellectual understanding since I'm building away happily anyway...
Edits: 04/02/16
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