WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
My friend is working on a tube linestage and have a series regulator, is that possible having the series regulator (6080, 6SL7 and OB2) feeding the Janus shunt regulator??
Set series up as a gyrator, low-pass of no specific voltage, I don't see a problem.
You wouldn't want series fighting shunt to set a slightly different "same" voltage.