chapter 23, page 925, halfway down the page they have a list of
variables and what they signify. They have one capital-R
subscript-?something? for "valve input resistance at working frequency".
I can't see what this is, in either the CD or my copy, in either the
useage in the equation or the definitions. IS this an "i" or a "t"? Or
smoething else? The only relevant entry I can find is in chapter 38,
page 1366, under (B) Valve and circuit, which lists a lowercase-r
subscript lowercase-i for "input resistance".... ?:|

DougC wrote:

chapter 23, page 925, halfway down the page they have a list of
variables and what they signify. They have one capital-R
subscript-?something? for "valve input resistance at working frequency".
I can't see what this is, in either the CD or my copy, in either the
useage in the equation or the definitions. IS this an "i" or a "t"?

It looks like a small t to me.
The only bother is that Rt does not appear in the equation
above the explanation notes, just , R1, R2 & Ro.

Maybe you just gotta build it and see if it works.

Patrick Turner.

Or
smoething else? The only relevant entry I can find is in chapter 38,
page 1366, under (B) Valve and circuit, which lists a lowercase-r
subscript lowercase-i for "input resistance".... ?:|

On Thu, 28 Apr 2005 16:54:49 -0500, DougC
wrote:

chapter 23, page 925, halfway down the page they have a list of
variables and what they signify. They have one capital-R
subscript-?something? for "valve input resistance at working frequency".
I can't see what this is, in either the CD or my copy, in either the
useage in the equation or the definitions. IS this an "i" or a "t"? Or
smoething else? The only relevant entry I can find is in chapter 38,
page 1366, under (B) Valve and circuit, which lists a lowercase-r
subscript lowercase-i for "input resistance".... ?:|

This is a Greek letter that I have long forgotten, and am too
lazy to look up. It stands for the equivalent input resistance
caused by cathode circuit inductance (I **** thee not), and
doesn't matter at audio frequencies.

Good fortune,

Chris Hornbeck
"Don't panic."

Chris Hornbeck wrote:

On Thu, 28 Apr 2005 16:54:49 -0500, DougC
wrote:

chapter 23, page 925, halfway down the page they have a list of
variables and what they signify. They have one capital-R
subscript-?something? for "valve input resistance at working frequency".
I can't see what this is, in either the CD or my copy, in either the
useage in the equation or the definitions. IS this an "i" or a "t"? Or
smoething else? The only relevant entry I can find is in chapter 38,
page 1366, under (B) Valve and circuit, which lists a lowercase-r
subscript lowercase-i for "input resistance".... ?:|

This is a Greek letter that I have long forgotten, and am too
lazy to look up. It stands for the equivalent input resistance
caused by cathode circuit inductance (I **** thee not), and
doesn't matter at audio frequencies.

Unless one uses a grounded grid circuit in a phono amp
where you have a highish gm j-fet driving the low Rin of a grounded grid
triode. This type of circuit has the tendency to become a
good oscillator at 100 MHz, so one has to treat it as an RF circuit
and carefully bypass things to prevent such oscillations.

Sould anyone try to drive a pentode connected grounded grid tube
with a j-fet, I wish then the very best of luck, since it is the land of
absurd outcomes ands wierd oscillation effects.

In such instances the gain of the fet between gate and source is less than
unity,
and the fet acts into a very low value load of the tube's cathode Rin,
so a small amount of inductance may well have a big significance.

Where the input device in cacode circuit has a high source or plate
impedance,
such as a j-fet, gain between the input and cascode tube load is very nearly
gm x RL, regardless of the
tube used.

So a 2sk147 with gm = 40mA/V with a 6DJ8 triode in cascode
powering a 20k load will produce an overall gain of 0.04 x 20,000 = 800.
If a 12AU7 or 12AT7 is used instead, gain stays the same.

The beauty of cascode circuits is that the input device acts will
very little gain in itself, so miller Cin is lower than if you try to use
the device for high gain to start with.
The grounded grid or grounded gate device following the input
device then also has very low Cin, circuit R is low, so
F reponse is very good.
But at the output of the second device, the outout resustance is very
high, usually a pure current source even if the output device is a
triode with low Ra.
So the load connected determines the Rout.
So if the load has inductance, and there is stray C, an LC resonant circuit
exists which may encourage RF oscillation.


Patrick Turner.




Good fortune,

Chris Hornbeck
"Don't panic."

Mebbe I just append all the previous chapters together, and then do a
search for "Rg", Ri" and "Rt" and see if any other instances come up....

Patrick Turner writes:
: DougC wrote:
:
: chapter 23, page 925, halfway down the page they have a list of
: variables and what they signify. They have one capital-R
: subscript-?something? for "valve input resistance at working frequency".
: I can't see what this is, in either the CD or my copy, in either the
: useage in the equation or the definitions. IS this an "i" or a "t"?
:
: It looks like a small t to me.

Agreed. Even under magnification.

: The only bother is that Rt does not appear in the equation
: above the explanation notes, just , R1, R2 & Ro.

It's quite clearly in the equation above that.
For optimum load impedance where µ 1.

Chris Hornbeck notes in
rec.audio.tubesll83711p212879hthcq7rljgs0sip8lmi2 @4ax.com:

: On Thu, 28 Apr 2005 16:54:49 -0500, DougC
: wrote:
:
: chapter 23, page 925, halfway down the page they have a list of
: variables and what they signify. They have one capital-R
: subscript-?something? for "valve input resistance at working frequency".
: I can't see what this is, in either the CD or my copy, in either the
: useage in the equation or the definitions. IS this an "i" or a "t"? Or
: smoething else? The only relevant entry I can find is in chapter 38,
: page 1366, under (B) Valve and circuit, which lists a lowercase-r
: subscript lowercase-i for "input resistance".... ?:|
:
: This is a Greek letter that I have long forgotten, and am too
: lazy to look up. It stands for the equivalent input resistance
: caused by cathode circuit inductance (I **** thee not), and
: doesn't matter at audio frequencies.

Hard to see a likeness from RDH to even lower case tau, the most obvious, or
iota, perhaps the next best without a cross bar - are you sure? I say "t" !

[there is a greek alphabeta[1] at p1397 RDH4]
[and on the web, along with useful pages on rendering t' same & maths ;-})]

: Good fortune,
:
: Chris Hornbeck
: "Don't panic."

Fine advice!
--
RdM

"Space isn't remote at all. It's only an hour's drive away
if your car could go straight upwards." -- Fred Hoyle

DougC desperately and mebbe even disparately aarghs in
:
: Mebbe I just append all the previous chapters together, and then do a
: search for "Rg", Ri" and "Rt" and see if any other instances come up....
Nah ... don't waste your time ... it's a lower case "t" in print, in RDH4 ...
Anomaly or not. Congrats on finding and pointing it out; it does seem odd...

What would the "t" stand for in the author's mind?

BTW, WRT publishing etc;- even rather representing;- you had an earlier post;

Brief searches even on Greek let alone maths throw up useful indications,

http://www.cs.tut.fi/~jkorpela/math/ and
http://donald.phast.umass.edu/kicons/greek.html for instance; a world ...

Take your time, and seek the best, as well as you can - and collaborate! ;=}))
--
RdM

: [there is a greek alphabeta[1] at p1397 RDH4]

[1] I was recently entranced in reading "Alpha Beta" by John Man.

RdM wrote:
DougC desperately and mebbe even disparately aarghs in
:
: Mebbe I just append all the previous chapters together, and then do a
: search for "Rg", Ri" and "Rt" and see if any other instances come up....
Nah ... don't waste your time ... it's a lower case "t" in print, in RDH4 ...
Anomaly or not. Congrats on finding and pointing it out; it does seem odd...

What would the "t" stand for in the author's mind?



Well I could not figure that out, but then you see--this is the reason
for the effort--to clear matters like these up one last time.

I don't always follow the math as I am working; if I find some character
unrecognizable I just look around the few pages before and after for any
use or explanation, or check the conventions in the back of the book.

Also I don't have an exact replica of the Greek symbols used, I elected
to just use the standard WindowsXP Linotype "symbol" font. I could
duplicate the Greek symbols in the custom font I made for some of the
special characters, but I think it's better to just stick with the
standard symbol font.

What I am considering is color-coding the final version: I have noticed
while working that there is a problem with recognizing different
characters in the maths presented. So maybe I am thinking: black for
regular symbols and letters, dark blue for numbers, dark green for Greek
symbols.... I don't like that a lowercase "L" looks like a "1", it makes
reading difficult. Of course the letters are always italicised in use
and the numbers NEVER are (in the book) but still.... I think perhaps
they were restricted by what the print-manufacturing processes could be
expected to handle at the time. -Or maybe the paper used was just cheap;
I also have a copy of Terman's 1943 Radio Engineer's Handbook, and the
actual printing of that seems much sharper than RDH4. The paper used in
the Terman book appears to be finished better, maybe that was the
difference.

Also in the (RDH4) book they italicised the Greek symbols, and I did not
do that with mine because the Linotype symbols often get much more
difficult to recognize when italicised. But then you have problems with
things like the uppercase Pi--which unitalicised, looks just like two
capital "I"'s next to each other. --If the version is intended as an
electronic reference anyway, then using colors should be all good, as
pretty much every consumer-level computer now has a color screen.

Printing is another matter and for that a black+white document only is
preferred, but I had assumed to do another layout version in black only,
for printing on a regular page....
~~~~~~~

DougC wrote:

The custom font content so far:
http://www.norcom2000.com/users/dcim...tuff_page.html

The font hinting I don't know how to do manually, but the automatic
software attempts seem to do well enough....

On Sat, 30 Apr 2005 00:57:18 +1200, RdM wrote:

Hard to see a likeness from RDH to even lower case tau, the most obvious, or
iota, perhaps the next best without a cross bar - are you sure? I say "t" !

It's obvious from context. It's only significant at very high RF
frequencies. Good references will be found in ARRL handbooks, etc.
Not an audio issue, but well understood in RF.

Interesting conceptually, though.

Chris Hornbeck
"Don't panic."

DougC wrote:
DougC wrote:

blah blah blah



-heh, the Audio Amateur/AudioXpress CD has the pages out of order: pages
978 through 983 run 978, 981, 982, 979, 980, 983....