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

Czech Martin Martin.Czech at micronas.com
Thu Aug 28 12:52:17 CEST 2003

Ok, my question was not correct in this meaning.
Of course audio tube circuits have often DC blocking,
or DC feedback which will create a very much different
signal for DC than that for -say- 100Hz.

Ok, the question should have been:

If I do a triangle input sweep (grid) with 100 and 10000 Hz,
and if I plot input voltage and output voltage (e.g.
by using scope with x/y mode), will I see a major difference?

I guess not.


> -----Original Message-----
> From: Antti Huovilainen [mailto:ajhuovil at cc.hut.fi]
> Sent: Donnerstag, 28. August 2003 12:38
> To: Czech Martin
> Cc: Sdiy (E-mail)
> Subject: Re: [sdiy] tube question 2: characteristics , DC versus 20kHz
> On Thu, 28 Aug 2003, Czech Martin wrote:
> > is it true that e.g. a triode stage large signal
> > characteristic measured at DC differs from
> > those measured at -say- 10kHz or 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.
> Antti
> Give a man a fire, and he'll be warm that day,
> Set him alight and he'll be warm for the rest of his life

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