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07-19-2023, 01:11 PM
Hi Guys
It is always preferable to have a separate PT or PT winding for bias supplies AND to use a full bridge rectifier and proper filtering, all of which provide a reliable source for the most important voltage in the tube amp WHILE allowing for proper grounding.
RBX covers this application and is powered from the 6V heater already in the amp.
BMK uses low-value pots and to power it from the plate winding would require a low-ish dropping resistor value of significant power rating. R would be 100k, say, made up from a couple of 220k in parallel, or better, three 330k in parallel, each 1W. The filters should be protected by a 100V zener, as the TUT3 projects show.
The RBX approach is used in TUT5's The Standard project, but using out-dated filter cap values (0ne-tenth what they should be).
It is always preferable to have a separate PT or PT winding for bias supplies AND to use a full bridge rectifier and proper filtering, all of which provide a reliable source for the most important voltage in the tube amp WHILE allowing for proper grounding.
RBX covers this application and is powered from the 6V heater already in the amp.
BMK uses low-value pots and to power it from the plate winding would require a low-ish dropping resistor value of significant power rating. R would be 100k, say, made up from a couple of 220k in parallel, or better, three 330k in parallel, each 1W. The filters should be protected by a 100V zener, as the TUT3 projects show.
The RBX approach is used in TUT5's The Standard project, but using out-dated filter cap values (0ne-tenth what they should be).
