06-10-2016, 08:04 AM
Most Rod Pentodes were designed to "still work" at 0.7V.
In contrast a DK91 / DK92 / DK96 / 1L6 is unreliable below 0.9V. The DK96 HF performance is poorer below 1.1V
At 0.7V it must be only about 70mW of power consumption?
I suppose over a 1000 hours from a D Cell. Why bother with an on/off switch?
If you examine the g2 current vs Anode current vs g1 voltage for Rod Pentodes, you can see why the usual technique of a simple resistor for screen grid fails badly, as Ia rises, the Ig2 falls to almost zero, so the Vg2 would rise to full HT. Hence the technique is either voltage tap, full HT (if it's a low HT) or a pair of resistors as voltage divider. g2 and Anode is almost a current mirror.
In contrast a DK91 / DK92 / DK96 / 1L6 is unreliable below 0.9V. The DK96 HF performance is poorer below 1.1V
At 0.7V it must be only about 70mW of power consumption?
I suppose over a 1000 hours from a D Cell. Why bother with an on/off switch?If you examine the g2 current vs Anode current vs g1 voltage for Rod Pentodes, you can see why the usual technique of a simple resistor for screen grid fails badly, as Ia rises, the Ig2 falls to almost zero, so the Vg2 would rise to full HT. Hence the technique is either voltage tap, full HT (if it's a low HT) or a pair of resistors as voltage divider. g2 and Anode is almost a current mirror.
