| Author |
Message |
Tim Williams
Guest
|
 Posted:
Mon Jan 17, 2005 1:24 am Post subject:
Reverse Mu (not for Mu Ron) |
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I doubt Ron will enjoy this, so I put a warning on it. ;)
http://webpages.charter.net/dawill/Images/ReverseMu.gif
Goal: high gain. Pentodes have the highest mu of any tube, since Rp is so
high. This often comes down due to the relatively small load resistors
commonly used, and although they still beat triode gain, it's no good if you
want gain concentrated like heat in a habanero pepper.
The 6U8 spec'd in the diagram has Rp = 200kohm and Gm = 5mmhos around this
range (resistor values chosen for 10mA bias) for a "mu" of 1000. The
problem is how to get this out -- a simple plate resistor would have to be
enormous (running from either high voltage or high current) and allow nearly
no drive capability. The answer is to bootstrap it with a cathode follower,
convieniently provided by the triode in the same envelope.
Note: although the 4.7k in the middle is bootstrapped to near Rp values,
limiting gain to probably 250-500, short of the 1000 maximum and near what
is possible at lower currents by a standard circuit, the triode makes up for
this by providing a low impedance output buffer capable of driving stiff
loads.
Now, we all know two CCS's fighting each other is terribly finicky, so we
need a way to stabilize it. Trimmers need constant attention. The answer
is NFB - local NFB, shunt in this case, directed to the grid. Mind you this
circuit assumes a stiff grid input, as the input capacitor provides the
feedback rolloff. You could just as well split the 1M and add a filter
capacitor inbetween, or add a grid leak from the 1M:220k divider to the
grid, filtering the divider.
Screen supply is also obtained from the follower; filtering provides a
rolloff and stiff AC screen supply while enhancing DC stability.
NFB feedback can be applied in series with the ground symbol, as done with
any other stage.
Predicted performance - should be able to do 200Vp-p from a +400V supply
into a small load. Stiffer loads like in the say, 10k range will draw more
current from the triode and limit it to maybe 100Vp-p. Lower still it will
be ultimately limited by the current capacity of around 30mAp-p.
Distortion won't be too pleasant, although I've got to imagine it wouldn't
be bad in the tens of volts range, as most tubes aren't. It might be 10% at
full output, but this is with maybe 0.2V input on the grid - too low to be
useful - add 20dB of NFB and you've got basically no distortion. Plus much
of the distortion cancels with that of the output stage.
This would be used on a simple two tube, two stage (well, three if you count
the CF, which would be fair since it contributes another itchy time
constant) SE amplifier with good gain, ample NFB and reasonable power (maybe
a sweep tube; something with more Gm than a 6L6, about the same power). Or
you could use it for driving a cathodyne, and y'know... I wonder if it
wouldn't be possible to run the top tube as a cathodyne......*trails off in
thought*
Or as a generic high gain stage where signal levels are small enough that
distortions will be miniscule. Phono to line level in one stage, eh?
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
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Ronald
Guest
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| Posted:
Mon Jan 17, 2005 4:21 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
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"Tim Williams" <tmoranwms@charter.net> schreef in bericht
news:z6AGd.7242$wa.5474@fe06.lga...
| Quote: | I doubt Ron will enjoy this, so I put a warning on it. ;)
|
Thanks ;-)) |
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John Stewart
Guest
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| Posted:
Mon Jan 17, 2005 7:24 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
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Tim Williams wrote:
| Quote: | I doubt Ron will enjoy this, so I put a warning on it. ;)
http://webpages.charter.net/dawill/Images/ReverseMu.gif
Goal: high gain. Pentodes have the highest mu of any tube, since Rp is so
high. This often comes down due to the relatively small load resistors
commonly used, and although they still beat triode gain, it's no good if you
want gain concentrated like heat in a habanero pepper.
The 6U8 spec'd in the diagram has Rp = 200kohm and Gm = 5mmhos around this
range (resistor values chosen for 10mA bias) for a "mu" of 1000. The
problem is how to get this out -- a simple plate resistor would have to be
enormous (running from either high voltage or high current) and allow nearly
no drive capability. The answer is to bootstrap it with a cathode follower,
convieniently provided by the triode in the same envelope.
Note: although the 4.7k in the middle is bootstrapped to near Rp values,
limiting gain to probably 250-500, short of the 1000 maximum and near what
is possible at lower currents by a standard circuit, the triode makes up for
this by providing a low impedance output buffer capable of driving stiff
loads.
Now, we all know two CCS's fighting each other is terribly finicky, so we
need a way to stabilize it. Trimmers need constant attention. The answer
is NFB - local NFB, shunt in this case, directed to the grid. Mind you this
circuit assumes a stiff grid input, as the input capacitor provides the
feedback rolloff. You could just as well split the 1M and add a filter
capacitor inbetween, or add a grid leak from the 1M:220k divider to the
grid, filtering the divider.
Screen supply is also obtained from the follower; filtering provides a
rolloff and stiff AC screen supply while enhancing DC stability.
NFB feedback can be applied in series with the ground symbol, as done with
any other stage.
Predicted performance - should be able to do 200Vp-p from a +400V supply
into a small load. Stiffer loads like in the say, 10k range will draw more
current from the triode and limit it to maybe 100Vp-p. Lower still it will
be ultimately limited by the current capacity of around 30mAp-p.
Distortion won't be too pleasant, although I've got to imagine it wouldn't
be bad in the tens of volts range, as most tubes aren't. It might be 10% at
full output, but this is with maybe 0.2V input on the grid - too low to be
useful - add 20dB of NFB and you've got basically no distortion. Plus much
of the distortion cancels with that of the output stage.
This would be used on a simple two tube, two stage (well, three if you count
the CF, which would be fair since it contributes another itchy time
constant) SE amplifier with good gain, ample NFB and reasonable power (maybe
a sweep tube; something with more Gm than a 6L6, about the same power). Or
you could use it for driving a cathodyne, and y'know... I wonder if it
wouldn't be possible to run the top tube as a cathodyne......*trails off in
thought*
Or as a generic high gain stage where signal levels are small enough that
distortions will be miniscule. Phono to line level in one stage, eh?
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
|
Providing a CCS (Pentode) with a CC Load is usually a misery, as you have
stated. The Q point quickly becomes indeterminate. Your circuit might work for a
while. It may need a stabilized heater supply to prevent it from wandering to
much!
Have Fun, John Stewart |
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Tim Williams
Guest
|
| Posted:
Mon Jan 17, 2005 8:28 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
"John Stewart" <jh.stewart@sympatico.ca> wrote in message
news:41EB21F0.FEC5B4AC@sympatico.ca...
| Quote: | Providing a CCS (Pentode) with a CC Load is usually a misery, as you have
stated. The Q point quickly becomes indeterminate.
Your circuit might work for a while.
|
Uh... did you see the DC gain of 4?
Very transistorey...heh...
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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Patrick Turner
Guest
|
| Posted:
Mon Jan 17, 2005 8:28 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
Tim Williams wrote:
| Quote: | I doubt Ron will enjoy this, so I put a warning on it. ;)
http://webpages.charter.net/dawill/Images/ReverseMu.gif
Goal: high gain. Pentodes have the highest mu of any tube, since Rp is so
high. This often comes down due to the relatively small load resistors
commonly used, and although they still beat triode gain, it's no good if you
want gain concentrated like heat in a habanero pepper.
The 6U8 spec'd in the diagram has Rp = 200kohm and Gm = 5mmhos around this
range (resistor values chosen for 10mA bias) for a "mu" of 1000. The
problem is how to get this out -- a simple plate resistor would have to be
enormous (running from either high voltage or high current) and allow nearly
no drive capability. The answer is to bootstrap it with a cathode follower,
convieniently provided by the triode in the same envelope.
Note: although the 4.7k in the middle is bootstrapped to near Rp values,
limiting gain to probably 250-500, short of the 1000 maximum and near what
is possible at lower currents by a standard circuit, the triode makes up for
this by providing a low impedance output buffer capable of driving stiff
loads.
Now, we all know two CCS's fighting each other is terribly finicky, so we
need a way to stabilize it. Trimmers need constant attention. The answer
is NFB - local NFB, shunt in this case, directed to the grid. Mind you this
circuit assumes a stiff grid input, as the input capacitor provides the
feedback rolloff. You could just as well split the 1M and add a filter
capacitor inbetween, or add a grid leak from the 1M:220k divider to the
grid, filtering the divider.
Screen supply is also obtained from the follower; filtering provides a
rolloff and stiff AC screen supply while enhancing DC stability.
NFB feedback can be applied in series with the ground symbol, as done with
any other stage.
Predicted performance - should be able to do 200Vp-p from a +400V supply
into a small load. Stiffer loads like in the say, 10k range will draw more
current from the triode and limit it to maybe 100Vp-p. Lower still it will
be ultimately limited by the current capacity of around 30mAp-p.
Distortion won't be too pleasant, although I've got to imagine it wouldn't
be bad in the tens of volts range, as most tubes aren't. It might be 10% at
full output, but this is with maybe 0.2V input on the grid - too low to be
useful - add 20dB of NFB and you've got basically no distortion. Plus much
of the distortion cancels with that of the output stage.
This would be used on a simple two tube, two stage (well, three if you count
the CF, which would be fair since it contributes another itchy time
constant) SE amplifier with good gain, ample NFB and reasonable power (maybe
a sweep tube; something with more Gm than a 6L6, about the same power). Or
you could use it for driving a cathodyne, and y'know... I wonder if it
wouldn't be possible to run the top tube as a cathodyne......*trails off in
thought*
Or as a generic high gain stage where signal levels are small enough that
distortions will be miniscule. Phono to line level in one stage, eh?
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms
|
The 1M/220k shunt FB network acts to reduce gain to a minimum
of around 5 if the signal source signal impedance is high.
But at DC, there will be shunt NFB applied to the pentode.
But if Rsource is low, sure, the gain is very high, about 1,000, or whatever the
u is for the pentode
At DC there will also be shunt NFB applied to the G2 circuit via the 33k from
output to
G2.
There is no need for either NFB loop if the top triode is biased from a fixed
bias voltage
of about 0.6 x B+, using a 1M R from the bias v to the triode G1, bottom pentode
is biased also with fixed bias via you 1M and 220k, and the 33k is swapped for a
resistor to B+
What you have here though is a bootstapped follower.
It would be possible to use such a circuit for phono.
Resistance loaded EF86 was often used for MM carts using an equalizing shunt
feedback network.
Quad22 and Leak and others did this one to save using tubes although
it never was as good as using a the pair of triodes in a 12AX7.
However, using the bootstrapped follower similar to Tim's gif,
the NFB network cab driven off what is a low impedance source so the NFB shunt
resistors need not load down the pentode and lower its open loop gain.
The usual technique starting from the phono socket is 100k to
the pentode G1, and 100k to 0V.
The signal voltage at G1 will always be very be low, since it is a "virtual
earth" signal potential,
so the cart is loaded by the two 100k in parallel, so cart loading is ok.
Then from the CF output, after the coupling cap, there is
an RC RIAA equalizing network.
The 6U8 data I have gives Ra = 400k and Gm = 5.2mA/V at 10 mA of Ia.
At 5mA, Ra will be higher, and Gm lower, and U will be about 2,100.
So the maximum gain at below 20 Hz can be dropped to say 500 with the resistor
networks in the RIAA
FB network, and then gain at 1 kHz will be say 50, and at 10kHz about 12.5, and
so on.
So for 3 mV input at 1 kHz, we'd get 150 mV of output.
Rout will be quite low.
Distortion at 1 kHz will be reduced 32 dB from what it is when gain is at 2,000,
so if was 0.5% at 1v output, expect 0.0125% at a volt of output, or about
as good as medium U triodes with a paassive eq filter and no NFB.
But this is a slightly better outcome than when using an EF86 with resistance
load,
since the NFB network loads down the pentode and reduces its open loop
and then reduces the amount of applied NFB by a large factor.
Unfortunately, pentode noise limits the use of such schemes to MM carts.
A whole different approach is needed for the better sounding moving coils
which have 20 dB lower output voltage but which is at less than 50 ohms source
impedance.
Tim's circuit can be used as a low gain triode line stage
if quite a few mods are applied.
1, apply fixed bias to the G1 pentode from a divider from the B+.
2, Get rid of the pentode Rk = 4.7k, and place whatever Rk is needed so
G1 can be bypassed to 0V in the normal way.
3, Don't use any bypass caps across pentode Rk,
4, Leave the 33k pentode G2 feed from the triode CF as is, but bypass the 33k
with an electro to apply the CF signal output to the G2 of the pentode.
5, Gain with 1 - 4 in place will be near the U of the pentode when connected
as a triode, and probably about 40, way too high for a line stage, when
only 8 may be needed.
So therefore use the same 100k + 100k input network as used for the phono
stage described above.
Only instead of the RIAA R+C shunt NFB network between CF output and pentode G1,
just use a gain setting resistance, about 820k will give closed loop gain of
about 8,
470k will give A' = about 4, and so on, and the FB resistor won't load down the
gain triode.
So because there is shunt FB to the input, and shunt FB to the pentode G2,
and because the triode is a CF, output resistance will be very low indeed,
lower than 1/ Gm of the triode, or less than 170 ohms, so can anyone tell me
what the Ro will be since there are a few maths experts amoung youse.
Patrick Turner. |
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John Stewart
Guest
|
| Posted:
Mon Jan 17, 2005 8:45 pm Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
Tim Williams wrote:
| Quote: | "John Stewart" <jh.stewart@sympatico.ca> wrote in message
news:41EB21F0.FEC5B4AC@sympatico.ca...
Providing a CCS (Pentode) with a CC Load is usually a misery, as you have
stated. The Q point quickly becomes indeterminate.
Your circuit might work for a while.
Uh... did you see the DC gain of 4?
Very transistorey...heh...
Tim
|
No problem, Tim. I simply noted the obvious. You may be successful with this
version.
Let us know the results.
Stabilized heater supplies were an absolute must in high gain DC coupled
amplifiers.
That gets worse for the SE version. Heater temp drift causing a few mv change
in
a high gain amp such as this might be difficult to control. So we will see!!
Cheers, JLS |
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Tim Williams
Guest
|
| Posted:
Mon Jan 17, 2005 11:19 pm Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:41EB4BAC.B594F549@turneraudio.com.au...
| Quote: | The 1M/220k shunt FB network acts to reduce gain to a minimum
of around 5 if the signal source signal impedance is high.
But at DC, there will be shunt NFB applied to the pentode.
But if Rsource is low, sure, the gain is very high, about 1,000, or
whatever the u is for the pentode
|
Yep.
| Quote: | There is no need for either NFB loop if the top triode is biased from a
fixed
bias voltage of about 0.6 x B+, using a 1M R from the bias v to the triode
G1
|
*Slaps forehead*
That'll work too. Just two different ways of skinning this cat..
| Quote: | Tim's circuit can be used as a low gain triode line stage
if quite a few mods are applied.
snip |
Yeah, but that changes the circuit entirely. If you want a line stage, use
a 12AU7 instead.
| Quote: | 5, Gain with 1 - 4 in place will be near the U of the pentode when
connected
as a triode, and probably about 40, way too high for a line stage, when
only 8 may be needed.
|
Like I said, only where you "need gain concentrated like a habanero pepper".
Have you ever even tasted a habanero? ;-)
| Quote: | So because there is shunt FB to the input, and shunt FB to the pentode G2,
and because the triode is a CF, output resistance will be very low indeed,
lower than 1/ Gm of the triode, or less than 170 ohms, so can anyone tell
me
what the Ro will be since there are a few maths experts amoung youse.
|
Ah, the polite way of saying "the final calculations will be left as an
exercise for the student." :^)
I would expect Zo to be reduced primarily by the CF, then second by the
loop. As you noted, open loop Zo will be around 1/Gm, then reduced further
by the shunt NFB, by perhaps a factor of 100 given a pentode mode device in
the bottom, giving SFA Zo!? Hmm.. I might have to build a beefier version
for headphone use!
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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Gregg
Guest
|
| Posted:
Tue Jan 18, 2005 3:36 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
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|
Hi Pat,
For us math dummies, can you say that again in english and in 50 lines or
less?
--
Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca |
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Patrick Turner
Guest
|
| Posted:
Tue Jan 18, 2005 5:50 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
Tim Williams wrote:
| Quote: | "Patrick Turner" <info@turneraudio.com.au> wrote in message
news:41EB4BAC.B594F549@turneraudio.com.au...
The 1M/220k shunt FB network acts to reduce gain to a minimum
of around 5 if the signal source signal impedance is high.
But at DC, there will be shunt NFB applied to the pentode.
But if Rsource is low, sure, the gain is very high, about 1,000, or
whatever the u is for the pentode
Yep.
There is no need for either NFB loop if the top triode is biased from a
fixed
bias voltage of about 0.6 x B+, using a 1M R from the bias v to the triode
G1
*Slaps forehead*
That'll work too. Just two different ways of skinning this cat..
|
I always like simplicity....
Don't keep slapping the forehead, it leeds to simplicity! :-]
| Quote: |
Tim's circuit can be used as a low gain triode line stage
if quite a few mods are applied.
snip
Yeah, but that changes the circuit entirely. If you want a line stage, use
a 12AU7 instead.
|
But it won't give you so much inner, or open loop gain to play with.
| Quote: |
5, Gain with 1 - 4 in place will be near the U of the pentode when
connected
as a triode, and probably about 40, way too high for a line stage, when
only 8 may be needed.
Like I said, only where you "need gain concentrated like a habanero pepper".
Have you ever even tasted a habanero? ;-)
|
I assume it tastes hot, and the best mexican restaurants have good smoke
extractor fans for their patrons.
I used to like a good dose of the hottest chilli sauce for my sambal at the
malay restaurants, and it acted as a great aphrodisiac with the woman I was
with;
she'd fuck a lot after it, but I never needed no encourangement from no pepper,
and now at a more gracious age my stomach tends to resent such things
deposited into it, whilst opportunities for lotsa fucking after pepper intakes
have all dried up.
I hope that answers your query.
Too much chilli results in a shunt feedback effect.
| Quote: |
So because there is shunt FB to the input, and shunt FB to the pentode G2,
and because the triode is a CF, output resistance will be very low indeed,
lower than 1/ Gm of the triode, or less than 170 ohms, so can anyone tell
me
what the Ro will be since there are a few maths experts amoung youse.
Ah, the polite way of saying "the final calculations will be left as an
exercise for the student." :^)
|
Just testing to see if any of the students are awake.
Heeeellloo, anyone here???
As long as the concept is grasped, it becomes obvious that
you have 3 FB networks all acting at once, and so Ro must be very low,
and less than an opamp.
| Quote: |
I would expect Zo to be reduced primarily by the CF, then second by the
loop. As you noted, open loop Zo will be around 1/Gm, then reduced further
by the shunt NFB, by perhaps a factor of 100 given a pentode mode device in
the bottom, giving SFA Zo!? Hmm.. I might have to build a beefier version
for headphone use!
|
Well you could.
But good HP amps still maintain correct loading for the tubes used, so
to get a match to 32 ohms, an OPT is still the best solution, rather than trying
to
fake it with a pentode current source with lots of NFB.
If you want a maximum of 1volt into 32 ohms, ( 31 milliW )
then you need 32 mA rms, so you need 50 mA of idle current
in something that can be turned right off or doubled, so
an EL84 with Ea of say 150v and 60 mA idle.
But its voltage gain will be only 0.32, hardly anything, and voltage NFB
of either shunt or series type is hard to arrange.
You need 3 volts input for 1 volt at the anode, and to reduce Ra down to
say 8 ohms means a shirtload of NFB has to be applied.
So the load value should remain at say 5k for the EL84, and output transformed
down.
Maybe a 6AS7 will do for a current supply element and you have a pentode driver
like 6AU6, or even better, 6BX6, or the more grunty 6EJ7
as a bootstrapped pentode drive as we have discussed.
Patrick Turner.
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Patrick Turner
Guest
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| Posted:
Tue Jan 18, 2005 6:34 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
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Gregg wrote:
| Quote: | Hi Pat,
For us math dummies, can you say that again in english and in 50 lines or
less?
|
Not sure what you mean.
You haven't quoted me here.
But hey, electronics was designed by the God of Triodes, not me,
and He made it barely comprehensible, to keep ppl struggling, lest too many
get things working too easily, without knowing what they were doing,
and that would have led to far greater numbers being electrocuted, like the
road toll.
So most ppl give up, and don't look harder and deeper at what puzzles them,
and leave complex things for the geeks and nerds to figure out.
Thank goodness I don't have to understand the schematic of my PC.
It'd cover the whole suburb with its masses of hyroglyphical cabalistic
symbols.
Don't ask me how my TV works.
The washing machine controller is another mystery.
If I knew a simpler way of explaining things *fully*, I would do it,
but I just can't always manage it.
It'd be REAL COOL if RDH4 was reduced to 20 pages of easy to understand
talk, but I doubt it could ever be done, and in fact to understand that book
you must really go to all the quoted references of at least 16,000 or more
pages
in publications now mostly forgotten and lost, and also spend years at uni
in courses of Triodology, and other 1955 Communications & Radio Theory
courses which no longer exist.
Sometimes I feel like I am in charge of a venerable old steam locomotive,
and one with lively and impressive performance.
Explaining its working and requirements as I travel the rail routes in
style to the fascination of onlookers places me in a bind.
How do I find time to correctly explain this behemoth,
and keep shovelling some coal in since the fireman got so old he died?
And I am always lookin for a damned water tap and hose, and coal is hard to
find......
I am currently looking for a position on a river steamer, where water can be
found,
and I will have an oil fired boiler, and where the life style is more
leisurely,
and gals can cruise up to me at the helm and take a turn or two.
Away from the rattle'n'bang of the tracks, I can have an auxilliary generator
with a pulley off the paddle wheel shaft and a
tube powered FM radio, and even a decent turn table to play sweet tunes
across my vessel's deck,
and babes will offer drinks to all aboard, as we glide gracefully on sunny
afternoons.....
Patrick Turner.
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Tim Williams
Guest
|
| Posted:
Tue Jan 18, 2005 6:53 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
"Gregg" <nospam@unknown.org> wrote in message
news:P5XGd.117333$KO5.46403@clgrps13...
| Quote: | For us math dummies, can you say that again in english and in 50 lines or
less?
|
Unfortunately, no. That's our Pat ;)
To sum up: high gain combined with a cathode follower combined with enough
NFB to bring it down to non-relativistic line stage gain levels gives
relativistic levels of Zo, for a tube...
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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Gregg
Guest
|
| Posted:
Tue Jan 18, 2005 8:35 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
|
|
Behold, Tim Williams signalled from keyed 4-1000A filament:
| Quote: | "Gregg" <nospam@unknown.org> wrote in message
news:P5XGd.117333$KO5.46403@clgrps13...
For us math dummies, can you say that again in english and in 50 lines
or less?
Unfortunately, no. That's our Pat ;)
|
LOL! True ;-)
| Quote: | To sum up: high gain combined with a cathode follower combined with
enough NFB to bring it down to non-relativistic line stage gain levels
gives relativistic levels of Zo, for a tube...
|
Ahhhh, si, comprendo! :-)
Thanks Tim.
--
Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca |
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Patrick Turner
Guest
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| Posted:
Tue Jan 18, 2005 9:40 pm Post subject:
Re: Reverse Mu (not for Mu Ron) |
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Gregg wrote:
| Quote: | Behold, Tim Williams signalled from keyed 4-1000A filament:
"Gregg" <nospam@unknown.org> wrote in message
news:P5XGd.117333$KO5.46403@clgrps13...
For us math dummies, can you say that again in english and in 50 lines
or less?
Unfortunately, no. That's our Pat ;)
LOL! True ;-)
To sum up: high gain combined with a cathode follower combined with
enough NFB to bring it down to non-relativistic line stage gain levels
gives relativistic levels of Zo, for a tube...
Ahhhh, si, comprendo! :-)
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There is no accounting for what ppl say they understand.
"relativistic"?
Its certainly not in RDH4 :-/
Nor is "shirtloads of overlapping NFB loops will reduce Ro to SFA ohms".
Maybe that's what Tim meant.
Patrick Turner.
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Gregg
Guest
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| Posted:
Tue Jan 18, 2005 11:59 pm Post subject:
Re: Reverse Mu (not for Mu Ron) |
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Behold, Patrick Turner signalled from keyed 4-1000A filament:
| Quote: | Gregg wrote:
Behold, Tim Williams signalled from keyed 4-1000A filament:
"Gregg" <nospam@unknown.org> wrote in message
news:P5XGd.117333$KO5.46403@clgrps13...
For us math dummies, can you say that again in english and in 50
lines or less?
Unfortunately, no. That's our Pat ;)
LOL! True ;-)
To sum up: high gain combined with a cathode follower combined with
enough NFB to bring it down to non-relativistic line stage gain
levels gives relativistic levels of Zo, for a tube...
Ahhhh, si, comprendo! :-)
There is no accounting for what ppl say they understand.
"relativistic"?
Its certainly not in RDH4 :-/
Nor is "shirtloads of overlapping NFB loops will reduce Ro to SFA ohms".
Maybe that's what Tim meant.
Patrick Turner.
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Tim speaks fluent Turnerese and Geekese, so it was a translation ;-)
--
Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca |
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Tim Williams
Guest
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| Posted:
Wed Jan 19, 2005 6:25 am Post subject:
Re: Reverse Mu (not for Mu Ron) |
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"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:41ED3C14.9C9977A6@turneraudio.com.au...
| Quote: | "relativistic"?
Its certainly not in RDH4 :-/
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Neither is SFA that I am aware of, they are both outside expressions.
I like "relativistic" because it means something whose velocity is Really.
Fucking. High. Within 10% of light speed, namely. The laws of physics
don't apply at this point and you get into formulas which this crazy-haired
German fellow figured out about a hundred years ago.
Tim
--
"I've got more trophies than Wayne Gretsky and the Pope combined!"
- Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms |
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