Discussions on RAT -
What about a series of discussions, that are surely at the
heart of the matter, dead on topic: Tubes

How to build that perfect tube with today's technology available ?

----------part A: pre-amp stage----------------
(B:line amp C: power amp
stage);
(JJ, EH, Shuanguang guys, please read along over our shoulders

You may or may not believe this, but I've witnessed a NG's
speculations and wishes end up in products, so , who knows ?

Here's the series 'tube-storm session' kick-off:
What way, to what spec's would your 'ideal' pre-amp tube be made ?

Rudy

"Ruud Broens"
..nl...

How to build that perfect tube with today's technology available ?


** They are all around you - they are called power mosfets.

Stick one in an evacuated glass bottle if you like.....




........... Phil

"Phil Allison" wrote in message
u...
** They are all around you - they are called power mosfets.

Stick one in an evacuated glass bottle if you like.....

Well, once you get rid of the 'grid' capacitance problems, not to
mention the gate breakdown problems... Then you need to figure out
how to keep it from melting, that radiative cooling inside a glass
bulb won't be very effective.

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"Tim Williams" wrote in message
...
"Phil Allison" wrote in message
u...
** They are all around you - they are called power mosfets.

Stick one in an evacuated glass bottle if you like.....


Well, once you get rid of the 'grid' capacitance problems,


** Only a problem for the terminally feeble minded like Tim..


not to mention the gate breakdown problems...


** Ever heard of a zener diode ?????


Then you need to figure out how to keep it from melting,


** Ever heard of a heatsink ???




........... Phil

"Ruud Broens" wrote in message
...
How to build that perfect tube with today's technology available ?

This isn't a very easy question because our experience is in the
electrical properties of the tubes, not the internal design of them.
If we all had some nice precision gear to build, evacuate and test
our own tubes that would be a different story...

One wish I've seen posted here was a triode KT90.. (I wonder how EI is
coming on that!)

Well let's see. What makes the perfect tube?
Triodes:
o Low plate resistance
o High gain
o Low capacitance (for easy driving)

The first goes hand-in-hand with perveance, which goes up with heater power.
Tubes like the 6V6 can't fight their way out of a tissue-paper
bag in triode mode, whereas 6AS7 and 6C33C, which take between 5 and 15
times more heater power, have very much lower Rp, and higher current
capability.
The second requires very precise grid spacing: a grid wound of fine
wires, closely spaced to each other and to the cathode for maximum effect.
It should be noted that very high Gm will make bias difficult because
any small change in bias voltage will cause a large change in current.
This goes counter to the third option, low capacitance. The best way
around this is to reduce the area (since you can't increase the distance),
such as in planar triodes. These babies can go up to 10GHz and above.
But they aren't real linear anyway. You also run into the problem of
heating the cathode, and reduced emission due to reduced cathode area.

For pentodes, the ideals a
o High plate resistance (towards infinity)
o High gain
o High current capability
o Low saturation voltage
o Low screen requirements

A lot of these were met with the late sweep tubes, 6KG6(?)/EL509 for
instance. The ones that were designed in the late 60s and early 70s.
Saturation (plate-curve knee) below 50V, high current, low screen,
high Gm. Rp doesn't seem very high, maybe 10k in some conditions, but
it should be kept in mind this is at like 900mA Ip! Better expressed
as a scaled number in that case.
If you ask me, they're like MOSFETs with magnified characteristics
(Vsat 50V vs. 2V), great HV characteristics (6~8kV peak), two extra
grids and a big farking heater (15-30W consumed depending on type).

Ah yes, the heater. The worst offender for tubes, it alone can ruin
the efficiency rating of an amplifier. (You might have 60% plate
efficiency, but counting total consumption of the amp, you'll have
maybe 40-50%!). A good reason that you should use tubes to their
fullest capability. You don't use a 6L6 to drive a 6V6. (I mean, Al
might, but we might just have to start calling him Weird Al instead! )

Which brings up another good point. What is perfect?

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"Phil Allison" wrote in message
. ..
** Ever heard of a zener diode ?????

Nope, don't have any. Besides, aren't they supposed to be putting them
in internally? Didn't they at one time? Why not any more?

Then you need to figure out how to keep it from melting,


** Ever heard of a heatsink ???

Err:

Stick one in an evacuated glass bottle if you like.....

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"Tim Williams" wrote in message
...
"Phil Allison" wrote in message
. ..
** Ever heard of a zener diode ?????

Nope, don't have any.


** Then you are an even dumber mother****er than ever.





........... Phil

On Sat, 01 Nov 2003 05:25:01 +0100, Ruud Broens wrote:

Discussions on RAT -
What about a series of discussions, that are surely at the
heart of the matter, dead on topic: Tubes

How to build that perfect tube with today's technology available ?

These guys know, but they'll wind up in Leavenworth if they tell you
the details:

http://sinh.nrl.navy.mil/code6840/code6840entry.html


slac.stanford.edu (Erik Jongewaard) wrote on Date: 1997/08/07 :
For ECRH (electron cyclotron resonance heating) magnetic confinement
fusion reactors use gyrotron oscillator tubes operating anywhere from 60
GHz to 240 GHz and 500 kW to 1 MW output for multi-second pulses. Try
that with a transistor (or lots of transistors for that matter)...


--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com

Being an engineer, I'm sure that thousands of VERY good technicians have
been working on this during the heydays of vacuum technology, and everything
that could be SENSIBLY done (and not only) has already been built . Then,
time has swept away most of the rubbish leaving only the "best" (economic,
dependable, fit-for-purpose...) tubes.
After all, the inside of a tube is a matter of micro-mechanics applied to
industrial scale, and in this fine art the world was much better some 40
years ago. As an example, I own four German cameras, Leicas, Voigtlaender
and Zeiss/Contax: well, not only the old Leica M4 but the oldest, "lowly",
Volks-camera from Voigtlaender is built to a much higher standard than my
new Leica M6 (which is a very good camera indeed, but the hand-machining
from a solid piece of metal of most pieces of the older ones make them just
of a class apart).
Take a look at a Telefunken EC86 or similar: You won't see grid wires unless
using a microscope. Or listen to an original Valvo AD1 or a RCA
"world-logo" 845, You simply cannot make anything sound better (unless You
rent the whole Berliner Philarmoniker....)
So, back to Your question: I think that the best tube is a remake of a
tried, tested and true good old TFK or RCA or GEC or Fivre tube, made with
the better alloys, the better vacuum, and the better quality controls
available thanks to today's technology, in order to achieve a better PRICE
too.
I'd love to get a REAL 845, not a Chinese beer bottle, for less than
50-60$....

Ciao

Fabio

Nevertheless, the idea of trying to influence the industry is good... at
least we should try.



"Ruud Broens" ha scritto nel messaggio
...
Discussions on RAT -
What about a series of discussions, that are surely at the
heart of the matter, dead on topic: Tubes

How to build that perfect tube with today's technology available ?

----------part A: pre-amp stage----------------
(B:line amp C: power
amp
stage);
(JJ, EH, Shuanguang guys, please read along over our shoulders

You may or may not believe this, but I've witnessed a NG's
speculations and wishes end up in products, so , who knows ?

Here's the series 'tube-storm session' kick-off:
What way, to what spec's would your 'ideal' pre-amp tube be made ?

Rudy

Hi RATs!

I build tube circuits and listen.

Only the sound matters to me.

Measurements are not in my sights.

No component is perfect. Some circuits may be, at least for a while

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Tim Williams wrote:

"Ruud Broens" wrote in message
...
How to build that perfect tube with today's technology available ?

This isn't a very easy question because our experience is in the
electrical properties of the tubes, not the internal design of them.
If we all had some nice precision gear to build, evacuate and test
our own tubes that would be a different story...

One wish I've seen posted here was a triode KT90.. (I wonder how EI is
coming on that!)

I contacted the EI factory a few times, telling them
thay could do worse than make a tube the same size as a KT90,
with 50 watts of plate dissipation, but a real triode,
with the same pinout at an EL34 or KT88, so
ppl could just plug a pair into an existing amp.
They agreed this would be a great idea, and that they were
already working on a prototype, to be called the 400B.
Last time I heard from them, the email was written
in a way that led me to believe the author was drunk.
I have not seen a 400B on the market place yet,
costing less than a KT88/6550, which it should be,
since there is one less electrode within.



Well let's see. What makes the perfect tube?
Triodes:
o Low plate resistance
o High gain
o Low capacitance (for easy driving)

The first goes hand-in-hand with perveance, which goes up with heater power.
Tubes like the 6V6 can't fight their way out of a tissue-paper
bag in triode mode, whereas 6AS7 and 6C33C, which take between 5 and 15
times more heater power, have very much lower Rp, and higher current
capability.
The second requires very precise grid spacing: a grid wound of fine
wires, closely spaced to each other and to the cathode for maximum effect.
It should be noted that very high Gm will make bias difficult because
any small change in bias voltage will cause a large change in current.
This goes counter to the third option, low capacitance. The best way
around this is to reduce the area (since you can't increase the distance),
such as in planar triodes. These babies can go up to 10GHz and above.
But they aren't real linear anyway. You also run into the problem of
heating the cathode, and reduced emission due to reduced cathode area.

A triode like the KT88 connected as a triode is one of the best triodes around.
A real triode, such as a 400B, able to be fitted
to all existing circuits would be nice.
Ppl say why bother, since we already have the 300B, and that's
a very usable tube, in terms of Ra, and linearity, (and the sound!).
There are supposed benefits of a directly heated cathode,
but I struggle to hear them.
So a 300B with indirectly heated cathode and octal socket, and smaller
glass bulb would be welcome, ie, the 400B.



For pentodes, the ideals a
o High plate resistance (towards infinity)
o High gain
o High current capability
o Low saturation voltage
o Low screen requirements

A lot of these were met with the late sweep tubes, 6KG6(?)/EL509 for
instance.

Only 35 watts anode Pdiss.
KT88 has 42 watts, and much better linearity.

imho, pentodes or beam tetrodes are only any good for audio hi-fi
when class A is used, and lots of NFB.



The ones that were designed in the late 60s and early 70s.
Saturation (plate-curve knee) below 50V, high current, low screen,
high Gm. Rp doesn't seem very high, maybe 10k in some conditions, but
it should be kept in mind this is at like 900mA Ip! Better expressed
as a scaled number in that case.
If you ask me, they're like MOSFETs with magnified characteristics
(Vsat 50V vs. 2V), great HV characteristics (6~8kV peak), two extra
grids and a big farking heater (15-30W consumed depending on type).

I don't mind mosfets for SS amps.



Ah yes, the heater. The worst offender for tubes, it alone can ruin
the efficiency rating of an amplifier. (You might have 60% plate
efficiency, but counting total consumption of the amp, you'll have
maybe 40-50%!).

You don't listen to efficiency.
a quad of KT88 consume 46 watts of power in the heaters.

That's less than one lousy 60 watt light bulb,
and so who cares about this when at any time during an evening,
maybe an average of 500 watts per hour are consumed by
TV sets, PCs, lights, and a host of other stuff, PER PERSON,
in a given household.
Many people use 24 KwH per day.

A good reason that you should use tubes to their
fullest capability. You don't use a 6L6 to drive a 6V6. (I mean, Al
might, but we might just have to start calling him Weird Al instead! )

Which brings up another good point. What is perfect?

What you percieve as perfection, is your perfection,
and perhaps nobody else's.

Patrick Turner.



Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"Ruud Broens" wrote in message news:3fa3350c$0$13887 How to build that perfect tube with today's technology available ?

You may or may not believe this, but I've witnessed a NG's
speculations and wishes end up in products, so , who knows ?

Rudy

One could build vacuum tubes without the need of a heater nowadays.
Have a look at these journals: Physics World, October 2000, page 25 to
26 or Physical Review Letters 2000 Vol. 85 page 864.. (also subsequent
articles by same) Two scientists, Vu Thien Binh and Christophe Adessi,
solved the problem of a room temperature thermionic emitter. They use
a 50 nm film of Titanium oxide on a nickel plate as a cathode. It has
a mere 0.1 electron volt thermal barrier which is satisfied easily by
just room temperature. The technique is robustly stable in the normal
vacuum tube environment against adsorbed surface contaminants as well
as ion bombardment. Since no heater or filament is required with this
technology, one can afford to use large planar cathode areas to make
high current tubes. The current density of the cathodes is quite good
also. No filaments to ever burn out. Maybe could even get some tube
manufacturer interested, although they probably prefer making tubes
that burn out.

The other amazing tube technology was just beginning to get started
when the whole tube area got eclipsed by SS in the 60s. This was the
beam deflection tube. These tubes are 1st order linear even with
actual load resistances, triodes are only linear with no load and 3/2
power law with loads below the Rp.

Don

"Fabio Berutti" wrote in message
news : Being an engineer, I'm sure that thousands of VERY good technicians have
: been working on this during the heydays of vacuum technology, and
everything
: that could be SENSIBLY done (and not only) has already been built . Then,
: time has swept away most of the rubbish leaving only the "best" (economic,
: dependable, fit-for-purpose...) tubes.

No doubt. That's part of why we lov'm !

: After all, the inside of a tube is a matter of micro-mechanics applied to
: industrial scale, and in this fine art the world was much better some 40
: years ago. As an example, I own four German cameras, Leicas, Voigtlaender
: and Zeiss/Contax: well, not only the old Leica M4 but the oldest, "lowly",
: Volks-camera from Voigtlaender is built to a much higher standard than my
: new Leica M6 (which is a very good camera indeed, but the hand-machining
: from a solid piece of metal of most pieces of the older ones make them
just
: of a class apart).
Any well-crafted tool or component is a pleasure to use, for sure.
On the matter of industrial processes now available to build with
high precision and repeatability - sure you're not disputing this is
orders of magnitude better than in those days ..

: Take a look at a Telefunken EC86 or similar: You won't see grid wires
unless
: using a microscope. Or listen to an original Valvo AD1 or a RCA
: "world-logo" 845, You simply cannot make anything sound better (unless You
: rent the whole Berliner Philarmoniker....)
: So, back to Your question: I think that the best tube is a remake of a
: tried, tested and true good old TFK or RCA or GEC or Fivre tube, made with
: the better alloys, the better vacuum, and the better quality controls
: available thanks to today's technology, in order to achieve a better PRICE
: too.
: I'd love to get a REAL 845, not a Chinese beer bottle, for less than
: 50-60$....

Great! Why reinvent the wheel, indeed. Some production improvements:
use borosilicate glass envelope ("pyrex"). use solid cermet heater block,
CVD coating isolation: zirconiumdioxine on top for 700 V cathode-heater
isolation. Surface-maximized cathode ("surface roughness") for optimum
bonded coating. Etc. Should give triple the emission of 'old tech' version
at the same heating power.
Cheers and thanks,
Rudy

: Ciao
:
: Fabio
:
: Nevertheless, the idea of trying to influence the industry is good... at
: least we should try.
:
:
:
: "Ruud Broens" ha scritto nel messaggio
: ...
: Discussions on RAT -
: What about a series of discussions, that are surely at the
: heart of the matter, dead on topic: Tubes
:
: How to build that perfect tube with today's technology available ?
:
: ----------part A: pre-amp stage----------------
: (B:line amp C: power
: amp
: stage);
: (JJ, EH, Shuanguang guys, please read along over our shoulders
:
: You may or may not believe this, but I've witnessed a NG's
: speculations and wishes end up in products, so , who knows ?
:
: Here's the series 'tube-storm session' kick-off:
: What way, to what spec's would your 'ideal' pre-amp tube be made ?
:
: Rudy
:
:
:
:
:

On Sat, 01 Nov 2003 15:33:15 +1100, the highly esteemed Phil Allison
enlightened us with these pearls of wisdom:


"Ruud Broens"
.nl...

How to build that perfect tube with today's technology available ?


** They are all around you - they are called power mosfets.

Well, why don't you leave us and go to rec.audio.mosfet. I'm sure you can
smoke some poles over there.

Stick one in an evacuated glass bottle if you like.....

Or inside Phil's head, if a really deep vacuum is desired...



.......... Phil

What a knob :-p


--
Greg

--The software said it requires Win2000 or better, so I installed Linux.

"Patrick Turner" wrote in message
...
:
: One wish I've seen posted here was a triode KT90.. (I wonder how EI is
: coming on that!)
:
: I contacted the EI factory a few times, telling them
: thay could do worse than make a tube the same size as a KT90,
: with 50 watts of plate dissipation, but a real triode,
: with the same pinout at an EL34 or KT88, so
: ppl could just plug a pair into an existing amp.
: They agreed this would be a great idea, and that they were
: already working on a prototype, to be called the 400B.
: Last time I heard from them, the email was written
: in a way that led me to believe the author was drunk.
: I have not seen a 400B on the market place yet,
: costing less than a KT88/6550, which it should be,
: since there is one less electrode within.
:
:
: A triode like the KT88 connected as a triode is one of the best triodes
around.
: A real triode, such as a 400B, able to be fitted
: to all existing circuits would be nice.
: Ppl say why bother, since we already have the 300B, and that's
: a very usable tube, in terms of Ra, and linearity, (and the sound!).
: There are supposed benefits of a directly heated cathode,
: but I struggle to hear them.
: So a 300B with indirectly heated cathode and octal socket, and smaller
: glass bulb would be welcome, ie, the 400B.
:
: Patrick Turner.

So anyone really close to Ei, where is that 400B ?
We wanna know !
Nice contributions there, Tim & Patrick.
Rudy




: Tim
:
: --
: "That's for the courts to decide." - Homer Simpson
: Website @ http://webpages.charter.net/dawill/tmoranwms
: