But the since the input signal is the noise at the power supply B+ connection, the power supply noise can be easily relayed to the cathode through a large valued electrolytic capacitor. And since the power supply noise frequency is  twice the line frequency and since harmonics seldom extend beyond the 5th, exceptional high frequency transmission is not necessary. In fact, the usual disadvantage, power supply noise leaking into the output of the grounded grid or cathode amplifier, works in our favor in a shunt regulator circuit and against us in a comparable series regulator. Furthermore, the need to offer the pentode's screen grid a clean AC path to ground also disappears, as triode connecting the pentode works to increase the effectiveness of a shunting pentode tube. And do forget the advantage all tube shunt regulators share: the shunting tube's heater does not require a separate power supply, as its cathode is at ground level.

    The appearance of the diodes (connected by dashed lines) will have many readers scratching their heads. They are there as a safety measure; should the output accidentally short to ground, they will become forward biased when the capacitor that is connected to the grounded grid stage's cathode attempts to becomes a negative 400 voltage source. Remember, always try to imagine the worst case scenario.
   We come this far, yet something is missing. So far all the examples have shown AC only shunt regulators. DC regulation can be implemented by paralleling the grounded grid stage's capacitor with a zener string and replacing the coupling capacitor to the shunting tube with a zener string that terminates into a resistor that leads to the negative power supply. Because this last arrangement will require much tweaking in construction and much adjustment in use, I would rather use an Op-Amp to adjust the DC portion of the regulator's output and let the tubes handle the AC portion where music falls. Two versions are shown below: the first is for shunting tubes that require a high negative bias and the second is for those tubes that do not.