[totojepast]

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595


-----
http://usenetove.koukat.cz/

[Scott Dorsey]

totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Al]

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the
tube characteristics, such as the ability to handle high power, might be
nice to have on a chip. With carbon nanotubes, acting as miniature
emitters of electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new
innovation in this regard is the development of an on-chip system of
vacuum triodes. Scientists at Agere Systems (a company spun off from
Lucent Technologies) build their chip using microelectromechanical (MEMS)
technology; a lateral field of carbon nanotubes is grown on a cathode
which can then be rotated into a vertical position in order to face a grid
(10 microns away) and anode (100 microns away). Radar, electronic warfare,
and satellite communications are expected to be the chief applications
areas. (Bower et al., Applied Physics Letters, 20 May 2002; contact W.
Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595


-----
http://usenetove.koukat.cz/

The problem with goodies like this is the fact that sputtering will take
place. As the electron winds moves from cathode to anode, it brings along a
little bit of the cathode. The transfer will result in degradation. In
vaccum tubes, it was not a real problem. In the nanoworld it may be.
Reliabily studies need to be done.

Al

[John Williamson]

totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

--
Tciao for Now!

John.

[John Larkin]

On Tue, 11 Dec 2007 14:40:02 +0100, "totojepast"
wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595


-----
http://usenetove.koukat.cz/



Nanotubes are erratic and noisy electron emitters, and tend to wear
out fast. This sounds like another parlor-game "breakthrough" that are
too common these days.

When there's an actual application, let us know.

John

[Scott Dorsey]

John Williamson wrote:

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

I still have kits to build several kinds, intended for amateur radio gear
with now-unavailable tubes.

I keep saying I'm going to design something like this for TV sweep tubes
too, but that's a non-trivial problem.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Stephen Cowell]

"Al" wrote
....

The problem with goodies like this is the fact that sputtering will take
place.

Sputtering nanotubes? That's the active element on the
cathode surface.

As the electron winds moves from cathode to anode, it brings along a
little bit of the cathode. The transfer will result in degradation. In
vaccum tubes, it was not a real problem. In the nanoworld it may be.
Reliabily studies need to be done.

Yes, of course... but the cathode chemistry of yesteryear
used a different effect (thoriated? emission) than buckytubes...
they're sharp, and they conduct, so they emit. Will they wear?
Don't know. Maybe *not*.
__
Steve
..

[John Williamson]

Scott Dorsey wrote:
John Williamson wrote:
Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

I still have kits to build several kinds, intended for amateur radio gear
with now-unavailable tubes.

I keep saying I'm going to design something like this for TV sweep tubes
too, but that's a non-trivial problem.

Good luck with that.

The ones I had in mind were something like an ECC83 replacement, only
needing (in some circuits) the heater pins connecting with a resistor.

It would have been handy at the time to be able to replace an EL84, as I
had a few pairs of those in output stages. I guess times have moved on
past the need for them, though.

--
Tciao for Now!

John.

[Lord Valve]

John Williamson wrote:

totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

--
Tciao for Now!

John.

That was the Fetron.

Developed for (by?) the phone company, to replace vacuum tubes
in equipment. They weren't robust when it came to HV spikes
(lightning strikes) like tubes were, so Ma Bell ****canned 'em.
They were offered by one of the major ham radio companies
(Collins?) for a short time, and also turned up in early Mesa-Boogie
guitar amps, where they were feared and hated by all. ;-) Mesa,
fortunately, included a switch which allowed the guitarist to
replace the Fetron with a 12AX7. I still run into a Fetron every
couple of years or so.

Here's a pic: http://www.telephonecollectors.org/p...s/?id=36365496

Lord Valve
Geetah Amp Fixer

[Lord Valve]

Are these naturally rad-hard like the glass ones?

LV




totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

-----
http://usenetove.koukat.cz/

[Dirk Bruere at NeoPax]

Scott Dorsey wrote:
totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott

Such a magnetron would probably operate at close to optical wavelengths.
Might as well get an LED

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

[Mike Rivers]

On Dec 11, 11:01 am, "Stephen Cowell" wrote:

Sputtering nanotubes? That's the active element on the
cathode surface.

No, that's the name of a new band.

[John Williamson]

Lord Valve wrote:


That was the Fetron.

Developed for (by?) the phone company, to replace vacuum tubes
in equipment. They weren't robust when it came to HV spikes
(lightning strikes) like tubes were, so Ma Bell ****canned 'em.
They were offered by one of the major ham radio companies
(Collins?) for a short time, and also turned up in early Mesa-Boogie
guitar amps, where they were feared and hated by all. ;-) Mesa,
fortunately, included a switch which allowed the guitarist to
replace the Fetron with a 12AX7. I still run into a Fetron every
couple of years or so.

Here's a pic: http://www.telephonecollectors.org/p...s/?id=36365496

They're the ones :-)

Shame they didn't work out. I vaguely remember more than one sort being
available on this side of the Atlantic.

--
Tciao for Now!

John.

[Jan Panteltje]

On a sunny day (Tue, 11 Dec 2007 14:59:14 +0000) it happened John Williamson
wrote in
:

totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

In Europe the lumince amplifier tube PL802:
http://www.radiomuseum.org/tubes/tube_pl802t.html
was at one time sold in a semiconductor version:
http://www.jogis-roehrenbude.de/Kuri...L802/PL802.htm

[Jeff Liebermann]

John Larkin hath wroth:

Nanotubes are erratic and noisy electron emitters, and tend to wear
out fast. This sounds like another parlor-game "breakthrough" that are
too common these days.

When there's an actual application, let us know.

John

The audiophile market will love them. Tube amps and pre-amps have
been hot sellers in the high end audio market.

For example, this CD player has 3ea 12AX7's and one 12AU7
http://www.audioadvisor.com/prodinfo.asp?number=1VICDS6
and sells for about $1500. There are plenty other audio products on
that site with tubes inside (search by keyword).


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[John Larkin]

On Tue, 11 Dec 2007 14:54:52 GMT, Al wrote:

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the
tube characteristics, such as the ability to handle high power, might be
nice to have on a chip. With carbon nanotubes, acting as miniature
emitters of electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new
innovation in this regard is the development of an on-chip system of
vacuum triodes. Scientists at Agere Systems (a company spun off from
Lucent Technologies) build their chip using microelectromechanical (MEMS)
technology; a lateral field of carbon nanotubes is grown on a cathode
which can then be rotated into a vertical position in order to face a grid
(10 microns away) and anode (100 microns away). Radar, electronic warfare,
and satellite communications are expected to be the chief applications
areas. (Bower et al., Applied Physics Letters, 20 May 2002; contact W.
Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595


-----
http://usenetove.koukat.cz/

The problem with goodies like this is the fact that sputtering will take
place. As the electron winds moves from cathode to anode, it brings along a
little bit of the cathode. The transfer will result in degradation. In
vaccum tubes, it was not a real problem. In the nanoworld it may be.
Reliabily studies need to be done.

Al

Nanotubes have been the rage for a decade or so now. Some day somebody
may find a use for them.

John

[Scott Dorsey]

John Williamson wrote:
Scott Dorsey wrote:
John Williamson wrote:
Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

I still have kits to build several kinds, intended for amateur radio gear
with now-unavailable tubes.

I keep saying I'm going to design something like this for TV sweep tubes
too, but that's a non-trivial problem.

Good luck with that.

The ones I had in mind were something like an ECC83 replacement, only
needing (in some circuits) the heater pins connecting with a resistor.

If you could still get high voltage JFETs, you could pretty much drop one
in place of an ECC83 without any problem.

But you can't. If you want that kind of voltage and that kind of current,
you are limited to MOSFETs. You can drop one in place of an ECC83 with
some additional bias resistors added, but it WILL take some additional
tinkering to set the bias and that may differ somewhat from circuit to
circuit.

It would have been handy at the time to be able to replace an EL84, as I
had a few pairs of those in output stages. I guess times have moved on
past the need for them, though.

Thing is, if you replace a power tube with a solid state tube of similar
transconductance, you still have the same heat issues that you did with
the tube. And if you use a higher transconductance device, you're going
to need to change the circuit a little.

Things like the EL84 and ECC83 work just fine and don't cost all that
much, so the demand to replace them with solid state equivalents just
isn't there. You could do it, if you really wanted to.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Tom Bruhns]

On Dec 11, 6:42 am, (Scott Dorsey) wrote:
totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I recall integrated "micro" vacuum "tubes" being touted 30 years and
more ago for use in instruments dropped into wells -- deep wells where
the temperature gets too hot for most solid state devices, and can be
used to excite emission from the tubes' cathodes.

Cheers,
Tom

[John Williamson]

Scott Dorsey wrote:

If you could still get high voltage JFETs, you could pretty much drop one
in place of an ECC83 without any problem.

But you can't. If you want that kind of voltage and that kind of current,
you are limited to MOSFETs. You can drop one in place of an ECC83 with
some additional bias resistors added, but it WILL take some additional
tinkering to set the bias and that may differ somewhat from circuit to
circuit.

Accepted, which is why the replacements had a PCB with a number of
components in them. A picture & schematic I've been pointed at on the
web shows 2 FETs, a couple of resistors & a capacitor on the board.
That's per triode, the picture was of a single triode, while the ECC83
was, IIRC, a double triode with a single heater.

They got pretty close, though, or so I heard.

It would have been handy at the time to be able to replace an EL84, as I
had a few pairs of those in output stages. I guess times have moved on
past the need for them, though.

Thing is, if you replace a power tube with a solid state tube of similar
transconductance, you still have the same heat issues that you did with
the tube. And if you use a higher transconductance device, you're going
to need to change the circuit a little.

It was more of a vibration sensitivity problem I had, to be honest.

Things like the EL84 and ECC83 work just fine and don't cost all that
much, so the demand to replace them with solid state equivalents just
isn't there. You could do it, if you really wanted to.
--scott

I don't need to, now. :-)

Solid state's now better sounding (IMHO) than valve technology. The
problem I had with the EL84 amps was the fragility of a valve in the
back of a van on the way to a gig as well as the weight of the output
transformer. The solid state version might have got round the fragility,
but not the weight. Now I just need a 1U sized rackmount power amp that
weighs a fraction of the amount which does an equivalent job.

As I said, technology's moved on...

I suppose in the sound field, the new triodes could be used as a compact
valve replacement, but how close to the classic valve transconductance &
other specs could they be made? How many volts can you use with a gap of
100 microns, mounted on silicon? The article mentions them currently
operating at 10 volts.

As has been said elsewhere in this thread, they seem to be a solution
looking for a problem. A bit like lasers were to start with, I think.
Uses will no doubt appear that nobody's even thinking of yet.

--
Tciao for Now!

John.

[[email protected]]

On Dec 11, 2:11 pm, Tom Bruhns wrote:
On Dec 11, 6:42 am, (Scott Dorsey) wrote:



totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I recall integrated "micro" vacuum "tubes" being touted 30 years and
more ago for use in instruments dropped into wells -- deep wells where
the temperature gets too hot for most solid state devices, and can be
used to excite emission from the tubes' cathodes.

Cheers,
Tom

Nuvistor, 13CW4, perhaps?

[Scott Dorsey]

John Williamson wrote:
Scott Dorsey wrote:

If you could still get high voltage JFETs, you could pretty much drop one
in place of an ECC83 without any problem.

But you can't. If you want that kind of voltage and that kind of current,
you are limited to MOSFETs. You can drop one in place of an ECC83 with
some additional bias resistors added, but it WILL take some additional
tinkering to set the bias and that may differ somewhat from circuit to
circuit.

Accepted, which is why the replacements had a PCB with a number of
components in them. A picture & schematic I've been pointed at on the
web shows 2 FETs, a couple of resistors & a capacitor on the board.
That's per triode, the picture was of a single triode, while the ECC83
was, IIRC, a double triode with a single heater.

They got pretty close, though, or so I heard.

You can. Back then, you could get higher voltage JFETs from Hitachi, but
those have all been discontinued. Getting discrete semiconductors today
is getting to be a lot harder than getting tubes.

Hmm. IGBTs would be interesting. Take some additional biasing too.

I don't need to, now. :-)

Solid state's now better sounding (IMHO) than valve technology. The
problem I had with the EL84 amps was the fragility of a valve in the
back of a van on the way to a gig as well as the weight of the output
transformer. The solid state version might have got round the fragility,
but not the weight. Now I just need a 1U sized rackmount power amp that
weighs a fraction of the amount which does an equivalent job.

As I said, technology's moved on...

The EL84 was never really intended for high vibration environments, but
the loctal tubes that were never really made it in the audio world.

I suppose in the sound field, the new triodes could be used as a compact
valve replacement, but how close to the classic valve transconductance &
other specs could they be made? How many volts can you use with a gap of
100 microns, mounted on silicon? The article mentions them currently
operating at 10 volts.

Actually VUDU Tube was trying to build some high voltage JFETs whose
curve carefully matched that of some standard tubes, even up in the
clipping region. They did one production run of them and they were
very impressive, but they could never get the financial backing to
get production fab done.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[It's that guy again...]

That was the Fetron.

When I received the 1st schematics from Boogie, it took a
while to find replacement 'FETRON' devices. They died a
quick death, and later a stronger FET (yes, even MOSFET)
was found to replace it, but the sound sucked donkey...

Developed for (by?) the phone company, to replace vacuum tubes
in equipment. They weren't robust when it came to HV spikes
(lightning strikes) like tubes were, so Ma Bell ****canned 'em.
They were offered by one of the major ham radio companies
(Collins?) for a short time, and also turned up in early Mesa-Boogie
guitar amps, where they were feared and hated by all. ;-) Mesa,
fortunately, included a switch which allowed the guitarist to
replace the Fetron with a 12AX7. I still run into a Fetron every
couple of years or so.

'NANO' tubes will not work at the higher voltages needed to make
it all MoJo. Current devices in the plate of V1 (NEVER another
stage, no way no how) works, but sounds like puke. Ya have to
understand WHY said tube sounds good for guitar input stages.

It's the case of tech fantasy trying to replace reality.

LEARN...!!!! Or be sold to...

I got a pile of FETRON devices collecting dust till I find
some old Boogie needing replacement. It'll cost ya big time.

JJTj






---------------------------------------------------
Nature's way is to take away from
those who have too much and give
it to those that have too little.

Man's way, on the contrary, is to
take away from those who have too
little to give more to those who
already have too much..

Lao Tsu, circa 490BC
---------------------------------------------------

[John Williamson]

Scott Dorsey wrote:

They got pretty close, though, or so I heard.

You can. Back then, you could get higher voltage JFETs from Hitachi, but
those have all been discontinued. Getting discrete semiconductors today
is getting to be a lot harder than getting tubes.

Hmm. IGBTs would be interesting. Take some additional biasing too.

Linearity might be a problem. Most of the ones I can find available are
designed for power switching. 50 amps at 1200 volts.

I don't need to, now. :-)

Solid state's now better sounding (IMHO) than valve technology. The
problem I had with the EL84 amps was the fragility of a valve in the
back of a van on the way to a gig as well as the weight of the output
transformer. The solid state version might have got round the fragility,
but not the weight. Now I just need a 1U sized rackmount power amp that
weighs a fraction of the amount which does an equivalent job.

As I said, technology's moved on...

The EL84 was never really intended for high vibration environments, but
the loctal tubes that were never really made it in the audio world.

I never got that far into it. I just carried a couple of spares. At
least they didn't need the bias adjusting after changing them, like
power transistors did then.
I could have a dead amp back up in seconds if it was just a dead valve.

I suppose in the sound field, the new triodes could be used as a compact
valve replacement, but how close to the classic valve transconductance &
other specs could they be made? How many volts can you use with a gap of
100 microns, mounted on silicon? The article mentions them currently
operating at 10 volts.

Actually VUDU Tube was trying to build some high voltage JFETs whose
curve carefully matched that of some standard tubes, even up in the
clipping region. They did one production run of them and they were
very impressive, but they could never get the financial backing to
get production fab done.

That could have been useful. Come to that, it could still be useful in
keeping the signal in the linear part of the curve, which is getting to
be a problem with some stuff.

--
Tciao for Now!

John.

[Andre Jute]

On Dec 11, 4:14 pm, Lord Valve wrote:
John Williamson wrote:
totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

--
Tciao for Now!

John.

That was the Fetron.

Developed for (by?) the phone company, to replace vacuum tubes
in equipment. They weren't robust when it came to HV spikes
(lightning strikes) like tubes were, so Ma Bell ****canned 'em.
They were offered by one of the major ham radio companies
(Collins?) for a short time, and also turned up in early Mesa-Boogie
guitar amps, where they were feared and hated by all. ;-) Mesa,
fortunately, included a switch which allowed the guitarist to
replace the Fetron with a 12AX7. I still run into a Fetron every
couple of years or so.

Here's a pic: http://www.telephonecollectors.org/p...s/?id=36365496

Thank you but I'll take the WE396A if it is all the same to you. For
what someone with brains and taste can do with a single agreeable
little WE tube per channel, check out my Type 68bis "Minus Zero" 417A
single tube micropower single ended amplifier, a glorious one-third
watt:
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg
http://members.lycos.co.uk/fiultra/t...17acircuit.jpg
Of course the T68bis "Minus Zero' with that huge one-third watt needs
high sensitivity speakers, so if you don't have any old VOT, check out
my Fidelio-pattern bicor horns, as in the T91 HWAF3 below:
http://members.lycos.co.uk/fiultra/K...20T91HWAF3.jpg
HWAF stands for High Wife Acceptance Factor, as the footprint is only
11in wide by 14in deep --- that's why I keep mine in my studio, for
fear my wife likes them so much that she grabs them...

Lord Valve
Geetah Amp Fixer

Those horrid Fetrons should not be inflicted even on axe murderers and
other guitar players; it is not humane.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Scott Dorsey]

John Williamson wrote:
Scott Dorsey wrote:

They got pretty close, though, or so I heard.

You can. Back then, you could get higher voltage JFETs from Hitachi, but
those have all been discontinued. Getting discrete semiconductors today
is getting to be a lot harder than getting tubes.

Hmm. IGBTs would be interesting. Take some additional biasing too.

Linearity might be a problem. Most of the ones I can find available are
designed for power switching. 50 amps at 1200 volts.

Yup, but the curves on them are actually pretty linear. The problem is
the bias points on them aren't anywhere near where you would want for
a tube.

You see them for switching, because that's what there is a demand for.
There are very few high power linear devices made out there, so everyone
has to make do with semiconductors intended for switching. For the most
part (well, except for SCRs and triacs) good linearity can be obtained with
careful biasing.

Actually VUDU Tube was trying to build some high voltage JFETs whose
curve carefully matched that of some standard tubes, even up in the
clipping region. They did one production run of them and they were
very impressive, but they could never get the financial backing to
get production fab done.

That could have been useful. Come to that, it could still be useful in
keeping the signal in the linear part of the curve, which is getting to
be a problem with some stuff.

All you need is to round up a venture capitalist....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Robert Baer[_2_]]

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595


-----
http://usenetove.koukat.cz/



There have been electron emitters (cathodes) made using IC fab
techniques for at least 10 years or more; in fact since they were active
devices, the emission rate was very controllable.

[John Williamson]

Scott Dorsey wrote:

Actually VUDU Tube was trying to build some high voltage JFETs whose
curve carefully matched that of some standard tubes, even up in the
clipping region. They did one production run of them and they were
very impressive, but they could never get the financial backing to
get production fab done.
That could have been useful. Come to that, it could still be useful in
keeping the signal in the linear part of the curve, which is getting to
be a problem with some stuff.

All you need is to round up a venture capitalist....

That's the hard part over here.

--
Tciao for Now!

John.

[Robert Baer[_2_]]

John Williamson wrote:

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the
tube
characteristics, such as the ability to handle high power, might be
nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new
innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a
lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and
anode
(100 microns away). Radar, electronic warfare, and satellite
communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

Which reminds me of a direct plug in replacement for some thermionic
valves made using FET technology a few years ago.

Whatever happened to them?

AFAIK both the AC and DC characteristics could not be made to match
any of the popular tubes.

[Robert Baer[_2_]]

Lord Valve wrote:

Are these naturally rad-hard like the glass ones?

LV




totojepast wrote:


Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. With carbon nanotubes, acting as miniature emitters of
electrons, this might be possible (See Update 454,
http://www.aip.org/enews/physnews/19.../pnu454-2.htm). A new innovation
in this regard is the development of an on-chip system of vacuum triodes.
Scientists at Agere Systems (a company spun off from Lucent Technologies)
build their chip using microelectromechanical (MEMS) technology; a lateral
field of carbon nanotubes is grown on a cathode which can then be rotated
into a vertical position in order to face a grid (10 microns away) and anode
(100 microns away). Radar, electronic warfare, and satellite communications
are expected to be the chief applications areas. (Bower et al., Applied
Physics Letters, 20 May 2002; contact W. Zhu, )

elements A follow-up to one of the articles in this update appeared in:
Update 595

-----
http://usenetove.koukat.cz/




Only when presented with a good looking hottie...

[Robert Baer[_2_]]

Dirk Bruere at NeoPax wrote:

Scott Dorsey wrote:

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html


Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott


Such a magnetron would probably operate at close to optical wavelengths.
Might as well get an LED

Except the *narrow* bandwidth would be a major advantage...

[Scott Dorsey]

flipper wrote:
On Wed, 12 Dec 2007 00:49:49 -0800, Robert Baer
wrote:

AFAIK both the AC and DC characteristics could not be made to match
any of the popular tubes.

How do you get a characteristic triode curve from a FET?

By tinkering with the shape of the channel, and by building composite
devices with multiple channels on one substrate.

I believe the VUDU Tubes guys have a patent on one method.

It should be possible to do with off-the-shelf FETs as well, by using
a bunch of parallelled devices at different bias points. Clumsy, though.

But it all depends on how closely you really need to match it. For the
IF strip of an communications receiver, you don't need a super careful
match and a single off-the-shelf FET would do.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

flipper wrote:

Don't have the same bias problem with depletion mode DMOS, like thee
one from supertex

http://www.supertex.com/pdf/datasheets/DN3545.pdf

http://www.supertex.com/pdf/datashee...erte x.com%22

Excellent! I have never seen these before! I just ordered some samples!
Many thanks for introducing me!
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Dirk Bruere at NeoPax]

Robert Baer wrote:
Dirk Bruere at NeoPax wrote:

Scott Dorsey wrote:

totojepast wrote:

Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html


Folks have actually been building MEMS tubes for a while now. You build
them small and you can get away with cold cathode since the
interlectrode
spacing is so small. And you can run them at low voltages for the same
reason. But you don't get a whole lot of current.

My guess is that these things will turn out to be most useful at RF, and
that the next step is for someone to develop a MEMS magnetron.
--scott


Such a magnetron would probably operate at close to optical wavelengths.
Might as well get an LED

Except the *narrow* bandwidth would be a major advantage...

Get a laser then.

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London

[Tim Williams[_2_]]

"Scott Dorsey" wrote in message
...
If you could still get high voltage JFETs, you could pretty much drop one
in place of an ECC83 without any problem.

Plate resistance?

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

[Scott Dorsey]

Tim Williams wrote:
"Scott Dorsey" wrote in message
...
If you could still get high voltage JFETs, you could pretty much drop one
in place of an ECC83 without any problem.

Plate resistance?

It's easy to add more series resistance. It's hard to remove it.

By "drop one in place" I am assuming some additional resistors, and maybe
some shunt caps too if you care about matching high frequency performance,
but all on a module that you can stick into a tube socket when a tube is
removed.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Tim Williams[_2_]]

"Scott Dorsey" wrote in message
...
Tim Williams wrote:
Plate resistance?

It's easy to add more series resistance. It's hard to remove it.

By "drop one in place" I am assuming some additional resistors, and maybe
some shunt caps too if you care about matching high frequency
performance,
but all on a module that you can stick into a tube socket when a tube is
removed.

My comment refers to the internal feedback that triodes have and pentodes
and transistors do not. I know of several circuits (though not commonly
used in commercial products) where that would make a huge difference.

I saw a post somewhere below that suggested a manufacturer was onto
compensation for this. I suppose a certain doping profile allows the JFET
"linear region" to extend to high voltages? This would approximate a
triode's characteristic better (roughly constant Rp), but not very linearly
(a JFET's "mu" varies widely with Vg).

The 12AX7/ECC83 is a excellent example of highly linear tube
characteristics, far in excess of any other device: mu is stone flat over a
200% variation in plate current. 6SL7 is somewhat better still.
Transconductance varies as a 3/2 power of plate current, as I recall, which
is less "curvey" than FETs or BJTs can claim. (For that matter, 12AX7 has
just as much transconductance as 2N3819 is guaranteed to have, which is
just silly. Not quite as much bandwidth though.)

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

[robert casey]

totojepast wrote:
Would you like that inside your amp?

http://newton.ex.ac.uk/aip/physnews.589.html

ON-CHIP VACUUM MICROTRIODE. Integrated, solid-state design had many
advantages over the old vacuum-tube style electronics. But some of the tube
characteristics, such as the ability to handle high power, might be nice to
have on a chip. A new innovation
in this regard is the development of an on-chip system of vacuum triodes.

Well, if this does work out, we could have D/A converters with on chip
analog "vacuum tube" buffers. Like the circuits I threw together using
an R2R ladder DAC and triode buffers in CD players, see
http://pw2.netcom.com/~wa2ise/radios/tubedac.htm

[Paul Stamler]

"Tim Williams" wrote in message
...

My comment refers to the internal feedback that triodes have and pentodes
and transistors do not. I know of several circuits (though not commonly
used in commercial products) where that would make a huge difference.

Internal feedback? Between what and what?

The 12AX7/ECC83 is a excellent example of highly linear tube
characteristics, far in excess of any other device: mu is stone flat over
a
200% variation in plate current. 6SL7 is somewhat better still.

And a 6SN7 will beat both of them, although at a lower mu. In fact, a 6SN7
is a remarkably clean device, operated open-loop.

Peace,
Paul

[Chris Hornbeck]

On Wed, 12 Dec 2007 13:15:13 -0600, "Tim Williams"
wrote:

My comment refers to the internal feedback that triodes have and pentodes
and transistors do not.

Oh no. Not again.

The 12AX7/ECC83 is a excellent example of highly linear tube
characteristics, far in excess of any other device: mu is stone flat over a
200% variation in plate current. 6SL7 is somewhat better still.

This is device-specific, but generally very true.

Transconductance varies as a 3/2 power of plate current, as I recall, which
is less "curvey" than FETs or BJTs can claim

The reason that this seems to contradict the 12AX7 above is because
Child's law applies to parallel infinitely large surfaces, among
many other assumptions. Real devices have their own (different)
exponents. The ideal 12AX7 has an exponent very near 1.0.

Thanks, as always,

Chris Hornbeck

[Tim Williams[_2_]]

"Paul Stamler" wrote in message
...
Internal feedback? Between what and what?

It's the electric field drawn between the plate and grid. Namely, that
which leaks through the grid wires. It's like putting a resistor divider
between plate, grid and cathode, but because it's electric, it doesn't cost
any current. Slick, eh?

Tighter grid spacings have higher Rp and mu as a result.

And a 6SN7 will beat both of them, although at a lower mu. In fact, a
6SN7
is a remarkably clean device, operated open-loop.

Actually, it won't: the curve of mu vs. Ip varies a bit more than 6SL7,
according to GE's datasheet. It's still pretty good though.

Obviously, it succeeds better at higher drive demands; a 6SL7 won't very
well drive a 22kohm load.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms