Well not a exactly a vacuum, they fill it with helium. "...NASA?s Ames Research Center is going back to the future with its new vacuum transistor ? a nanometer-scale vacuum tube that, in early testing, has reached speeds of up to 460GHz."
And for the audiophools, > There?s no word on whether these vacuum-channel transistors will allow for the creation of small, modern audio amplifiers that sound like original tube amps ? but maybe!
Mikek :-)
amdx wrote on 11/1/2017 8:42 PM:
Why would anyone care if they sound like tube amps? We can get all the tube amps we want.
I thought they had recreated the sound of tubes digitally, no?
-- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
The problem with field emission is that it destroys the tips. The e-field gradients have to be so high to rip electrons that it rips molecules too.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
An extensive search of field emission showed no mention of molecules ripped from the cathode. However, numerous articles discussed cathode damage from residual ionized gasses. These bombard the cathode and destroy the single atom tips.
An intriguing possibility is very close electrode spacing that allows operation in atmospheric pressure. I have come across a number of articles describing this, but cannot find any references in a brief search.
At high fields, atoms are ripped from a tip. I wasted a lot of time on tomographic atom probing, which does exactly that.
Field emitters, and field emitting triodes, have been played with for decades. A sharp tip would be an ideal point source of electrons for an electron microscope, operating in ultra-high vacuum, but the tips don't last. The compromise is to heat the tip, which really makes it a low-temperature thermionic cathode where the high field helps emission.
This is one of those recurring fads like fuel cells.
And more press-release fodder.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
On a sunny day (Wed, 1 Nov 2017 19:42:09 -0500) it happened amdx wrote in :
With enough helium and enough transistors maybe NASA will finally rise towards the planets... Or transistors floating everywhere :-)
But really it is just a trillions(tm) part of the field emission display:
Note the word: Non Linearity.
NASA should just build HUGE THINGS like nuclear powered spacecraft that brings us through the galaxy, NASA is worse than toys-r-us.
And those huge spacecraft need no shitty little non-linear fragile cosmic ray sensitive tinker toy transistors. All over for NASA
SpaceX is the way to go.
And Russia of course.
Oh, and China.
China first on mars?
Hot field emission sources last longer than cold ones.
Electric arcs depend on that fact that if you get a surface hot enough under a high electric field it distorts in a way that produces a lot of very sharp spikes which are sharp enough to act as field emission tips.
Hot field emission sources don't run quite that hot, but they do self-clean and self-sharpen to some extent.
They aren't as stable and don't last as long as single crystal lanthanum boride source, but they are appreciably brighter, and are definitely commercially available.
In the sense that you can buy fuel cells and field emission electron guns of the shelf.
It's not so much a fad as a niche market. If John Larkin can't sell it, he sees it as a fad.
Not to mention advertising brochures.
-- Bill Sloman, Sydney
It wouldn't work for audiophools. The noise from nearby quasi particles popping in and out of existence could be overwhelming.
Regards,
Boris Mohar
Got Knock? - see: Viatrack Printed Circuit Designs (among other things)
void _-void-_ in the obvious place
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That was a bit of a joke. As I understand, in blind tests golden hears do no better than chance on A/B listening tests. The difference becomes noticeable only when over driven then the tube amps have a preferred sound over transistors. But, my ears rolloff at about 11kHz... My 20 year old daughter didn't like the 15,750hz coming from an old TV we had. Mikek
Am 02.11.2017 um 15:09 schrieb amdx:
No self-respecting Golden Ear would ever participate in a blind test. They find the weirdest excuses.
cheers, Gerhard
I thought that there were two real parts to the "tube sound" (excluding the imaginary parts) - a bit of second order distortion, and nicer behaviour near saturation (with non-linear behaviour that gives less harsh cutoffs).
The first effect is audible and apparently can be easily identified by people used to tube amps - I am neither an audiophool or an audiophile, and can't talk from personal experience. It is, of course, purely subjective whether you like this added distortion or not.
The second effect means you don't need such an over-dimensioned amp with tubes when you want to get drums and cymbals to sound right (as they can give volume peaks that are much higher than the average level).
Both of these effects can be achieved in transistor amps, but need something a bit more than a simple A/B design.
There's another issue that affects the sound with popular non-hifi valve ki t: 50/100Hz modulation. I've reproduced the effect with a basic audio amp I C. It does make a fair difference.
NT
ith its new
rly
fets
second or third order has to do with symmetry in the amplifier, not if it's made with tubes or transistors
except for the gain stage in a guitar amplifier there is no reason to add d istortion, the weak link is going to be the speakers anyway
tube amps are big a heavy, and power is hardly a problem anymore
distortion is deliberately used for a few reasons, and used to be widely used unintentionally with beneficial effect on the sound. My experiment demonstrated that nicely.
NT
And we can't digitally emulate overdrive distortion of tubes?
-- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
ith its new
rly testing,
fets
acuum-channel
iers
eund
we had.
It seems like we should be able to, in theory, however, if there is a solid state guitar amp that does this well I am unaware of it. I am open to sug gestions, if anybody has any, as my life would be simpler if I didn't need to maintain and lug around tube amps.
I have a Line 6 Pocket POD, it was about $150 street price a couple years ago. I've been playing around 20 years and have used a lot of different amps; whatever "circuit emulation" DSP technology they're using is really well done and it pulls off a very uncanny simulacrum of say a cranked Marshall head through a 4x12" cabinet, that responds to your playing and control adjustments in the way you'd expect a real amp would. But you can listen thru headphones.
Put the output in a full mix and I doubt many people could tell the difference. The only downside is it seems extremely power-hungry and will suck a quad of AAA batteries to nothing in about two hours even with the display backlight off, so it's nice they also included an input for an external DC adapter
Define for me the nature of the "tube" sound and I will create a filter to provide that sound.
-- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
its new
ts
wards the planets...
It wasn't NASA that killed Project Orion.
Mark L. Fergerson
So you add 10dB to the transistor amp and don't do that (clip).
Don't know about mine anymore but it would surprise me if they were that good.
When I was a kid, I could walk by a house on the sidewalk and tell if there was a TV on in the house.
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