[Paul G.]

On Tue, 11 Nov 2008 00:30:45 +1100, "Phil Allison"
wrote:


"Paul Goose "

grrrrrrrr



......snip......

The resistor noise voltage generated, is on the anode circuit for
your tube, if you use the input noise voltage for a typical low noise
tube (12AX7), you have about 450nv (bw=1Hz) effectively at the grid.

** uh ????????

The EIN of a 12AX7 is in the order of 2uV in the audio band.

This equates to only **14nV ** per rt Hz !!



You're correct, 2uv is about right for a 12AX7, my figures are 1.8
uv from 25Hz to 10KHz (RCA manual). The question is.... is it pink or
white noise? Assuming it to be pink, normalizing to 1 Hz, means 4
decades drop, or about 400 nv. Assuming it to be white, means it is
reduced by roughly sqrt(10000), or 100, giving a value about what you
say, approximately 14nv.
White or pink is relevant to this thread, because the original
posting was concerned with low frequency.


Paul G.