[sdiy] tube question 2: characteristics , DC versus 20kHz

[Grant Richter]

> It is true for the often used bypassed cathode configuration (which will
> give you roughly twice the gain at frequencies higher than the RC cutoff
> point). Other than that the tube parasitic capacitances have some effect,
> but you can calculate the effect yourself. Typical capacitances are shown
> in the datasheets.

Has anyone seen a configuration where a zener diode is used in the cathode
circuit of an inverting triode stage? I saw an old app. note where a zener
is used as a "grid voltage regulator". It replaces the cathode resistor and
bypass cap. It allows you to adjust the tube operating point, using only a
single supply.

It seems necessary if a tube circuit is to handle +/- 5-10 volt signals at
the grids.