Hi:
I have been recently been searching for information about the uses of vacuum today. For all I have found, they seem to have niche applications on RF High power, microwave and X-Rays production and general high power output stages. Because I'm thinking about creating a Tesla Coil with vacuum tubes (for the high power output) I realized that I dont know why they are used at high powers. I mean, we got a 811A vacuum tube that can handle about 230 Watts for 21 dollars. However, for 1 dollar I found the MJL3281AG that can do pretty much the same thing! At around what power output does it make sense to use tubes?
Thanks!
1 dollar I found the MJL3281AG
It is the frequency you can do it at where the vacuume tubes win. FET technology is constantly pushing this but at high powere at high frequency you still need a tube.
As it is a moving target it is hard to say where the break point is.
So for example for a Tesla Coil with a resonant of 1 Mhz would be the tube a good choice? Or something like a FM transmitter? Or is it way higher frequencies?
Interesting post. I'd have called the use of vacuum tubes in audio equipment a niche application because in practically all objective terms, solid state is superior. I see, incidentally, you can still buy brand new tube based headphone amplifiers for $20 or so.
However, I'd not have called microwave power products like microwave ovens a niche application. I guess it'll be some time before we see a solid state version of a 750 Watt Klystron tube in consumer electronic products.
The microwave oven uses a magnetron.
Allan
. I see, incidentally, you can still buy brand new tube based headphone amplifiers for $20 or so.
I believe that's a gimmick for people who think tubes sound better. In most of these cheap little tube preamps/headphones the tube is operated at low plate voltage and little or no gain... Notice the ICs on the board.
Guitar players like the way tubes sound when driven into distortion and you do see lots of tube guitar amps.
Some audiophiles think tubes sound better, and there are some very expensive tube audio amplifiers. But the truth is, it's a LOT cheaper & easier to make an amplifier with low-distortion, low noise, and flat frequency response using modern electronics.
DVDdoug:
I believe that's a gimmick for people who think tubes sound better.
I think it's usually a case of the end result of audio eventually getting picked up by the listener ..... a combo of distortion effects from the tube amplifier, their ears, the head-phones themselves, and their own preference about what 'sounds' 'better'.
Now, as for valves/tubes ....... (for the OP) ..... power output, power handling, efficiency, size, weight, frequency of operation, and voltage levels used..... are some considerations. Eg...... consider hundreds of kilowatt, or many kilovolt.
For your own application..... if size, price of no concern, and if the device you use does the job, then ok. If you find something smaller and gets the job done more cheaply, etc.... also ok.
Unlike solid state devices, vacuum tube electronics are pretty resistant to the EMP (electromagnetic pulse) emitted by nuclear weapons, so they may come in handy soon.
Hang on to those tubes!
jremington:
Unlike solid state devices, vacuum tube electronics are pretty resistant to the EMP (electromagnetic pulse) emitted by nuclear weapons, so they may come in handy soon.Hang on to those tubes!
Nice!! All-analog F-22 !!
jremington:
Unlike solid state devices, vacuum tube electronics are pretty resistant to the EMP (electromagnetic pulse) emitted by nuclear weapons, so they may come in handy soon.Hang on to those tubes!
With some tiny amount of care taken with the design, solid-state is always going to be more reliable than tubes, even with high EMP. Since you have to be close to a nuclear explosion to get that level of EMP, I suspect that the blast is going to break the tubes or at least disturb them in their sockets.
And, other than audio amplifiers, what useful electronics can you make with tubes, which you are going to want to have available after an EMP? An Arduino built from tubes would be room-sized. Not exactly a "wearable".
Since you have to be close to a nuclear explosion to get that level of EMP, I suspect that the blast is going to break the tubes or at least disturb them in their sockets.
If I'm THAT close to a nuclear blast, I can't really say I'd be to concerned about any electronics, and besides, they would probably be 4 blocks over wrapped around a tree.
And, other than audio amplifiers, what useful electronics can you make with tubes, which you are going to want to have available after an EMP? An Arduino built from tubes would be room-sized. Not exactly a "wearable".
RF amp. I operated/maintained a tube driven 2kw HF transmitter. Of course it doesn't really matter if the radio works if you don't have anything to power it.
Vacuum tubes come into their own for high power RF, such as radio/TV transmission and particle accelerators,
heres about the largest device I know of, its mind-boggling, just the the heater alone takes 10kW of power:
And on the very small scale people are experimenting with nano-tube based silicon devices using
thermionic emission: NASA melds vacuum tube tech with silicon to fill the terahertz gap | Ars Technica
And there is research in using thermionic emission in the solid state for high temp. solar cells too I believe.
And there are a lot of exotic tubes used for radar such as TWTs and klystron variants, and a (legendary?)
device that can generate an EMP itself, the vircator.
Of course it doesn't really matter if the radio works if you don't have anything to power it.
Or anyone to listen to it.
what useful electronics can you make with tubes, which you are going to want to have available after an EMP?
Simple radio transmitter and receiver. One tube each for CW code transmission would be sufficient for many purposes, given the radio silence that will once again reign.
Thanks!
That resolved all my doubts.
allanhurst:
The microwave oven uses a magnetron.Allan
A magnetron is a vacuum tube. A simple diode, actually...
jremington:
Unlike solid state devices, vacuum tube electronics are pretty resistant to the EMP (electromagnetic pulse) emitted by nuclear weapons, so they may come in handy soon.Hang on to those tubes!
Vacuum tubes are also very rugged and very forgiving (as far as overloads are concerned).
A mistuned transmitter, for example, can have red-hot glowing plates and when it cools down and is tuned properly, still works fine.
Do that to a transistor RF final and you will release the magic smoke and hear the shattering of beryllium oxide substrates before light can travel 11 inches.
Tubes still have their place, and even today a lot of audiophiles claim that vacuum tube amplifiers and vinyl records sound better than mosfets and digital data.
I'm not an "audiophile", but I do agree... tubes do sound better. They are "smoother"... kinda like a really good mug of beer.
tinman13kup:
RF amp. I operated/maintained a tube driven 2kw HF transmitter. Of course it doesn't really matter if the radio works if you don't have anything to power it.
Ever heard of "Field Day"?
DVDdoug:
Guitar players like the way tubes sound when driven into distortion and you do see lots of tube guitar amps.
Real fuzz (i.e. a tube amp driven to clipping) always sounds better than those stupid back-to-back diode "fuzz boxes".
6v6gt:
However, I'd not have called microwave power products like microwave ovens a niche application. I guess it'll be some time before we see a solid state version of a 750 Watt Klystron tube in consumer electronic products.
How can a guy with a 6V6 as his avatar confuse a klystron with a magnetron?