The tube is still good and will give full MP3). Glass power tubes often do not have flashed getters. Instead, they use a metal getter device, usually coated with zirconium or titanium which has been purified to allow oxidation. These getters work best when the tube is very hot, which is how such tubes are designed to be used. The Svetlana A and SV use such getters. The most powerful glass tubes have graphite plates. Graphite is heat-resistant in fact, it can operate with a dull red glow for a long time without failing.
Graphite is not prone MP3) secondary emission, as noted above. And, the hot graphite plate will tend to react with, and absorb, any free oxygen in the tube.
The Svetlana SV series and B use graphite plates coated with purified titanium, a combination which gives excellent gettering action. A graphite plate is much more expensive to make than a metal plate of the same size, so it is only used when maximum power capability is needed. Large ceramic tubes use zirconium getters. Since you can't see a "flash" with such tubes, the state of the tube's vacuum has to be determined by electrical means sometimes by metering the grid current.
A typical glass audio tube is made on an assembly line by people wielding tweezers and small electric spot-welders. They assemble the plate, cathode, grids and other parts inside a set of mica or ceramic spacers, then crimp the whole assembly together. The electrical connections are then MP3) to the tube's base wiring. This work has to be done in fairly clean conditions, although not as extreme as the "clean rooms" used to make semiconductors.
Smocks and caps are worn, and each workstation is equipped with a constant source of filtered airflow to keep dust away from the tube parts. Once the finished assembly is attached to the base, the glass envelope can be slid over the assembly and flame-sealed to the base disc. A small glass exhaust tube is still attached, and enters the envelope.
The tube assembly is attached to a processing machine sometimes called a "sealex" machine, an old American brandname for this kind of device. The exhaust tubing goes to a multistage high-vacuum pump. The sealex has a rotating turntable with several tubes, all undergoing a different step in the process.
See more pictures of glass tube assembly and production. If you want to control a LOT of power, a fragile glass tube is more difficult to use. So, really big tubes today are made entirely of ceramic insulators and metal electrodes. Otherwise, they are much the same inside as small glass tubes--a hot cathode, a grid or grids, and a plate, with a vacuum in-between. In these big tubes, the plate is also part of the tube's outer envelope.
Since the plate carries the full tube current and has to dissipate a lot of heat, it is made with either a heat radiator through which lots of cooling air is blown, or it has a jacket through which water or some other liquid is pumped to cool it. The air-cooled tubes are often used in radio transmitters, while the liquid-cooled tubes are used to make radio energy for heating things in heavy industrial equipment.
Such tubes are used as "RF induction heaters", to make all kinds of products--even other tubes. Ceramic tubes are made with different equipment than glass tubes, although the processes are similar. The exhaust tubing is soft metal rather than glass, and it is usually swaged shut with a hydraulic press.
All the equipment for exhausting and conditioning the tube is much larger, since there is more volume to exhaust, and the large metal parts require more aggressive induction heating. The ceramic parts are usually ring-shaped and have metal seals brazed to their edges; these are attached to their mating metal parts by welding or brazing.
Many big radio stations continue to use big power tubes, especially for power levels above 10, watts and for frequencies above 50 MHz. The reason is cost and efficiency--only at low frequencies are transistors more efficient and less expensive than tubes. Making a big solid-state transmitter requires wiring hundreds or thousands of power transistors in parallel in groups of 4 or 5 at a time, then mixing their power outputs together in a cascade of combiner transformers.
Plus, they require large heat-sinks to keep them cool. An equivalent tube transmitter can use only one tube, requires no combiner which wastes some powerand can be cooled with forced air or water, thus making it smaller than the solid-state transmitter. This equation becomes even more pronounced at microwave frequencies. Nearly all commercial communication satellites use a traveling-wave tube for their "downlink" power amplifiers.
The "uplink" ground stations also use TWTs. And for high power outputs, the tube seems to reign unchallenged. Exotic transistors still are used only for small-signal amplification and for power outputs of less than 40 watts, even after considerable advances in the technology. The low cost of RF power generated by tubes has kept them economically viable, in the face of advancing science.
In general, only very low-cost guitar amplifiers and a few specialized professional models are predominantly solid-state. Especially popular with serious professional musicians are modern versions of classic Fender, Marshall and Vox models from the s and s.
Why tube amplifiers? It's the tone that musicians want. The amplifier and speaker become part of the musical instrument. The peculiar distortion and speaker-damping characteristics of a beam-tetrode or pentode amp, with an output transformer to match the speaker load, is unique and difficult to simulate with solid-state devices, unless very complex topologies or a digital signal processor are used.
These methods apparently have not been successful; professional guitarists keep returning to tube amplifiers. Even the wildest rock musicians seem to be very conservative about the actual equipment they use to make their music. And their preferences keep specifying the proven technology of vacuum tubes. The recording studio is somewhat influenced by the prevalence of tube guitar amps in the hands of musicians.
Also, classic condenser microphones, microphone preamplifiers, limiters, equalizers and other devices have become valuable collectibles, as various recording engineers discover the value of tube equipment in obtaining special sound effects.
The result has been huge growth in the sales and advertising of tube- equipped audio processors for recording use. Although still a minor movement within the multi-billion-dollar recording industry, tubed recording-studio equipment probably enjoys double-digit sales growth today. At its low point in the early s, the sales of tube hi-fi equipment were barely detectable against the bulk of the consumer-electronics boom. Yet even in spite of the closure of American and European tube factories thereafter, since the sales of "high-end" audio components have boomed.
And right along with them have boomed the sales of vacuum-tube audio equipment for home use. The use of tubes in this regime has been very controversial in engineering circles, yet the demand for tube hi-fi equipment continues to grow. Bias is a negative voltage applied to a power tube's control grid, to set the amount of idle current the tube draws.
It is important to bias a tube to stay within its rated dissipation. Many times we have customers asking us things like, "I replaced the tubes, the old tubes ran at 35 mA, the new ones run at 38 mA. I'm worried that I have to rebias the amp. Especially with guitar amps--they tend to run their tubes at idle conditions which are conservative. Some high-end audio amps run their power tubes quite MP3) that case, rebiasing is necessary.
Tubes and semiconductors show us that more than one way to make an active device exists. In the s and s, there were lots of technologies for building logic with cool names like cryotrons, flux-summation-cores, electroluminescent-photoconductor logic, tunnel diodes, transfluxors, ferractors, and parametrons, using everything from superconductors to microwaves.
The point is that many technologies beyond tubes and semiconductors were tried, but transistors won. A lot. Some of them were really elaborate. There were lots of unusual tubes. My favorites were the magic eye tubes … so many variations.
Question for author: why is this a video. The only picture is a tube, which could be a JPG. And the audio, well it could be text so we could read it at our own pace and later find it via google. Youtube monetization. Everyone wants to be a YouTuber nowadays, damned be documenting and detailing thoroughly. A lot of us read things in environments where sound would be intrusive or impractical or on machines with no speakers connected. Also video is just about the worst medium for technical documentation unless there is some complex mechanism or operation that needs demonstrating.
Most casual viewers do not want a wall of text and still pictures. Video is the way to engage. Videos MP3) shitty. No real search, they require all your time, they are usually much slower than what I can read. This is at best. But everyone can make a video, thank cellphones and youtube for that. No, I do not deny that good videos can be engaging. Unfortunately good videos are rare, and require actually much more effort than editing a wall of text and snapping few pictures.
The real speed bottleneck would be the wiring between tubes. Including poor wiring I would give it 10MHz or less. All coaxial wiring should get it to MHz or so. The wiring is probably most of the difference though there will be a extra delay for the carry out bit. Try us!
Give us a call today at and find out for yourself why we are 1. Whether you need vacuum tubes for industry, hi-fi applications, ham radio, old time radio, or any other purpose, we will be the only supplier you will ever need. The majority of our orders ship within twenty-four hours. After your order is received, we hand test each vacuum tube TWICE to make sure it is exactly up to the manufacturer's specs before it is ever sent to you. Nothing leaves our warehouse without this service!
Our customer loyalty is legendary and for good reason. Once a customer buys from us, he stays with us. We also have a large supply of used vacuum tubes in stock We stock radio and vacuum tubes for every application from all major manufacturers including RCA, GE, Sylvania, Raytheon, Tungsol, and Amperex. Please Click Here to MP3) our eBay store. Your shopping cart is empty. My Cart. You have no items in your shopping cart. Enter your email to sign up for our newsletter:.
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