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

[Czech Martin]

compared to the usual cathode resistor - grid resistor - automatic
biasing this will deliver lower dynamic resistance at the cathode
(less local feedback) at high grid bias.
Thus more amplification for this purpose. Makes sense.

m.c.

> -----Original Message-----
> From: Grant Richter [mailto:grichter at asapnet.net]
> Sent: Donnerstag, 28. August 2003 17:29
> To: Antti Huovilainen; Czech Martin
> Cc: Sdiy (E-mail)
> Subject: Re: [sdiy] tube question 2: characteristics , DC versus 20kHz
> 
> 
> > 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.
> 
> 
>