RE: More on space charge - no harp content

["Michelle LeFree" <mlefree@xxxxxxxxxxxxx>]

IronMan Mike, you never cease to amaze me.  This time you delivered a fine
explanation on the action of tubes:
> Actually, there's a very good reason the old tube amps sound so good.
Tubes
> have a softening effect.  It's because of something known in engineering
> circles as "space charge".  I'll give a very basic explanation.  Bear with
> me and you'll understand.  Questions entertained after the lecture. <big
snip>

Thanks for your explanation; I enjoyed it very much.  As long as we are on
the subject, it might interest readers who also enjoyed it that "space
charge" plays a key role in the production of x-rays.  With x-ray tubes, in
the family of cathode ray tubes, the electrons making up the space charge
are also "boiled" off the cathode, pass the grid and then collide with the
anode.  With x-ray tubes there is a high enough voltage (in the
multi-kilovolt range) applied between the cathode and anode to impart
sufficient energy to the electrons in the space charge to cause x-rays to be
formed when they interact with the atomic structure of the anode.  I suspect
that vacuum tubes also emit low levels of x-rays.

Also interestingly, TV picture tubes are cathode ray tubes, too.  Since they
work with similar principles as the x-ray tube they also produce x-rays
(albeit as a side-product as x-rays are a bad thing if they aren't used for
a purpose).  With TV tubes, the anode is just inside the surface of the
screen where the phosphor layer resides.  The phosphors emit the visible
light that makes the picture when struck by the electron beam.  (TV tubes
are a bit more complicated than other cathode ray tubes because they include
focusing electrodes that sweep the electron beam back and forth across the
screen to make the picture.)

The unwanted x-rays that are emitted by video tubes are a very good reason
to keep your young'ns at least several feet away from the TV set while they
watch their cartoons for hours on end.  I doubt that there is significant
enough x-ray exposure from the vacuum tubes in our amps to cause concern.

Keep 'em coming, Mike!

Thanks, Michelle