danger of runaway tube current when amplifier is unattended
is minimized.
Also since most bias voltage supply filter networks tend to
be very simple single diode or half wave, there is usually a great deal
of ripple in the most sensitive signal path in the amplifier – the
grid! And active bias system is also an opportunity to design a bias
supply with extremely low levels of ripple. This adds a sense of
stillness and low-level detail not obtainable with standard bias
voltage supplies.