New type of vacuum tube

Apparently as long as there is some sort of thermionic device somewhere in the signal chain, a gadget inherits "tube sound."

I'd expect the amplification factor to be low in a VF display, ballpark 1. And they are generally run positive-grid.

-Lasse

Here's a better picture:

It's a tube. The linear filament, the two hex waffle grids, and the anodes are clear. It's really just a spin on the standard VF display construction. I suspect it's terrible electrically, but that's what tube sound is best at, being terrible.

Maybe they do have phosphor on the two anodes. That would be cute. The amps could have a window on the front so you could see your toob glowing.

Standard tubes could have phosphor on the inner surface of the plates. I donate this idea to the public domain.

How about an LED driving a photomultiplier somewhere in the signal chain? Pay the usual reviewers to rave about the sound and charge big bucks.

And if you have a pair in class AB they'll glow more or less depending on sound level!

OR, if you use a really fast-decaying phosphor, you'll be able to pick up the sound from across the room with a photodiode and a telescope. For no useful purpose, but hey -- tubes.

Yeah, one could arrange for a light show. We want distortion, so we wouldn't run class A.

Photo-optical compressors with tube gain stages are all the range in music production, and actually I'm not sure that's all audiophoolery - they do kind of have a nice "sound".

Toob-tech WiFi!

Mark L. Fergerson

People who disagree speng alot of money to "prove" otherwise.

Recently I sold a pair of wrecked monoblock Mac copies to a guy in Chicago for the transformers. Maily the ouptu transformers which were Chicago BO-15 s. These not only had the screen grid taps, they also have the cathode wind ings whichj was a McIntosh exclusive. apparently they had a patent on it be cause my Uncle who built them said the patent had run out on those special transformers.

Tell you this much, those were the most solid state sounding tube amps I ev er heard. Maybe there was a diffeence when they clipped.

there has to be a difference when a tube amp c lips because any back EMF ge nerated by the inertia of the speaker cone ois quickly damped by a semicond uctor junction whether it is bipolar or FET. In fact the diodes across bipo lar outputs are there to prevent slipping from imposing reverse voltage on the B-0E junction as far as I know. that probably accounts for the differen ce.

The problem with this audiophoolery is that you are not supposed to clip th e amp. There should be no difference any other time. they used to take a sm all tube guitar amp to big rock concerts sometimes and actually put a micro phone in front of them to get "that" sound. Probably someting only Les Paul could describe.

Anyway, these Mac copies reproduced turntable rumble really well, something I had never seen a tube amp do before.

Those new tubes, someone will probably take yto building headphone amps wir th them or soemthing like that. That is thre new fad. I am tryingt o find a niche in there somewhere, like maybe a DC coupled tube amp for electrostat ic headphones. Or they might be used in guitar amps.

Before you condemn the audiophols though, have a lok at guitar amps. They g ot tube uinput with bipolar outp[ut. they got tube input with FET output. T hey got solid state with tube outputs. They got solid state with tube outpu ts and one tube for "channel two" for overdrive. they got all kinds of s*it that no audiophools would even consier. I just recently got into the field and was surprisd at all the different topologies used. Damn. These people are nuts.

Seems AudioPhools LOVE distortion: note "generating the same rich harmonics" in the article.

They also crow "dramatically reducing its size" and patently ignore the Nuvistor design which is also rather small, but also rated for outer space and has excellent radiation resistance.

Also, they say "less than 2% of power required by conventional vacuum tubes" and totally ignore the 1R5 and 1U5 (ALSO SMALL) that uses 1.5V filament voltage. In that vein,they could have used a semiconductor for the emitter in place of the filament - THAT wold have been innovative...

Lastly, there is the "replaced regularly like a 12AX7" comment; once every 8-12 years does not exactly fit the implication of "very often".

Yep! The Nuvistors.

nd a link at the moment. "

You mean for amplification ? That would be weird. And that spawns a questio n that might result in a small hijack.

I saw the development of plasma TVs. I se how they work, they have an arc a nd the duration of the ar deterrmines the brightness of that pixel. OK, tha t is one way to do it.

but I alays wondered why they didn't just build huge VFDs to accomplish the same thing. I am fully aware there would be a great deal of complexity but look at the plasma TV. It would be no worse, that's for sure. the same tec hnology used in the logic board of a plasma or the Tcon of an LCD would dri ve a VFD just fine. and I think it would be more efficient.

One of the main things that eastys power in a plasma is the fact that they have to put out a couple of hundred volts with a fast slewing rate, and the capacitance is a considerable load. Whether is is worse than a deflection yoke is debatable because the same size plasma pulls a similar amount of po wer as a regular three CRT based projectiopn TV did.

But why didn't they just scale up the VFD technology for flat screen TVs ?

Especially at that price!

Filament current probably. Don't even small displays require a couple hundred mA?

A VF teevee would need two huge slabs of glass, fairly far apart. A zillion strands of filament, a grid array, and an anode array stacked inside. Vacuum inside, so the stress on the glass would be huge. It would be heavy, like a big CRT or plasma display. Long filaments might be a problem too.

There have been some color (real color, by pixel) VF displays but they are rare.

LCDs are amazing and keep getting better and bigger and cheaper.

VFs, like CRTs, are a dying technology.

I'm seeing what looks like a filament wire, running along the length of the "tube". There's an open chicken-wire-like structure which looks a lot like a large-area grid. This is all quite similar to what you will see inside a VFD (which is essentially a triode)... and as others have pointed out, Noritake is a well-known name in VFD construction.

So, my guess is that it is indeed a thermionic valve.

It looks interesting. The same frit-seal that is used for vacuum fluorescent displays (and is still in mass production) applied to thermiionic triodes. The picture looks like a dual triode.

The old Nuvistors had hard-to-beat input capacitance, leakage, and static insensitivity. For applications like a field mill, this sort of thing could be a viable replacement for that niche. It'd have to be commercially available, though...

It would be cool if that VF technology could do something more sensible than emulate a 12AX7.

How about some sort of microwave device, like a planar TWT or klystron? Distributed amplifier? Farnsworth multipactor oscillator?

A parallel-plate photomultiplier should be possible.

Pulsed UV source?