Electron tube DF97 at low supply potential?

At your risk.
Take safety precautions.
A fuse should always been used in series with a battery for fire protection.


An dvantage of such electron tubes is the low filament current consumption, typically less than 25mA if underheating is used.


Some preliminary measurements were done today. DF96 has not been tried yet.


Supplying 1.5V at filament cathode.


Then control grid left open (at space potential).


Then screen grid used as anode electrode.


Vg2        Ig2
9V          0.1μA
18V         1μA
27V        18μA
36V      106μA
48V      350μA


Vb is approximate as 9V batteries were used in various discharge state.


Then an 8.2MΩ was connected between Vb and grid for pull up bias or Pleiades Bias.


Vg2          Ig2
9V            26μA
18V        122μA


A microphone booster amplifier such as Pleiades V6 should be possible even at Vb=9V.



See also:


Operating features of the Audion - E. H. Armstrong