Just Who Makes Tubes These Days?

For most of us, electronic technology comes in the form of solid state devices. Transistors, integrated circuits, microcontrollers. But for the first sixty years or so of the field existing, these devices either hadn’t been invented yet or were at too early a stage in their development to be either cost-effective, or of much use. Instead a very different type of electronic component ruled the roost, the vaccum tube.

A set of electrodes in an evacuated glass envelope whose electrical properties depended on the modulation of the flow of electrons through them, these were ubiquitous in consumer electronics up until the 1960s, and clung on in a few mass-market applications even as far as the mid 1970s. As cheaper and more versatile semiconductors superseded them they faded from electronic parts catalogues, and the industry that had once produced them in such numbers disappeared in favour of plants producing the new devices. Consumer products no longer contained them, and entire generations of engineers grew up never having worked with them at all. If you were building a tube amplifier in the early 1990s, you were a significant outlier.

Alive And Kicking In The 21st Century

The warm glow of a tube amplifier lends credibility to an audiophile set-up. Hannes Grobe / CC BY-SA 4.0
The warm glow of a tube amplifier lends credibility to an audiophile set-up. Hannes Grobe / CC BY-SA 4.0.

As our consumer electronics have become ever more digital in their make-up, interest has blossomed in analogue devices, or at least devices with a visibly analogue component. In particular the world of audio has begun to chase the elusive “tube sound”, whether it be in the context of intentionally overdriven amplifiers for the guitarist, or closer to perfect ones for the audiophile.

High-end hi-fi shops are full of tube-based devices, and a plethora of tube amplifier kits are available for the electronics enthusiast. Tubes can be bought under a bewildering array of brands often at eye-watering prices, something of a surprise for a technology which might be presumed to have disappeared over four decades ago. This does raise an interesting question though, with such a large number of tube brands on the market, where are they all made, and how have their manufacturers survived for so long? The answer is relatively straightforward, yet in other aspects a story of labyrinthine complexity.

High-power transmitting tubes never went away. Angeloleithold (CC BY-SA 3.0)
High-power transmitting tubes never went away. Angeloleithold (CC BY-SA 3.0)

While consumer vacuum tubes might have disappeared from mundane electronics decades ago, it’s first worth pointing out that many of the old names in the vacuum tube business didn’t stop manufacturing vacuum tubes, they simply stopped making the tubes you might be familiar with. There are industrial applications in which vacuum devices are very much still with us , even though in many cases they have semiconductors snapping at their heels.

High power RF amplifiers for UHF and higher frequencies for example still use vacuum tubes, be they specialised planar tubes or slightly more exotic fare such as klystrons. Similarly there are specialised RF applications that still use travelling wave tubes, and very high power industrial equipment that uses vacuum and gas-filled tubes for control or rectification.

But who is making the “normal” tubes — the smaller glass-envelope tubes, small triodes and pentodes such as you’d find in that guitar amplifier? We recognize some names from times past such as Telefunken or Mullard, others are modern brands such as JJ or Fender’s Groove Tubes brand, and others are clearly Russian or Chinese names such as Svetlana, SovTek, “Winged C“, or Shuguang. Clearly there are not as many tube factories left in the world as there are logos stamped on the glass of imported tubes, so what on earth is going on?

A Technology For The Few, Not The Many Any More

The answer is that the consumer tube business in 2020 is no longer a commodity component market producing the lifeblood of a million televisions and radios, instead it’s a boutique operation serving a niche market. Looking at the tubes available, it’s clear that if you are searching for an obscure 1050s small-signal RF tube you’ll be out of luck; these are mostly audio amplifier parts, double triodes, output pentodes, even the occasional power rectifier, and at costs that would raise an eyebrow or two for buyers of their originals.

A current-manufacture Mullard-branded ECC83 (12AX7) general purpose small signal double triode for example costs $43.20 (£35.09) in 2020, while browsing a 1957 copy of Wireless World we find the same part number advertised for 8 shillings and thruppence, which is £0.41 ($0.51) in post-decimalisation British money. Using the Bank of England’s inflation calculator that comes out at about £9.96 ($12.27) today, so the modern re-issue is more than three times as expensive as was the genuine article in its heyday. This is evidently a business with a significant mark-up, and the world’s remaining tube factories are cashing in.

A selection of Mullard ECC83s from back in the day.
A selection of Mullard ECC83s from back in the day.

Investigating further, we find that tube manufacture of this type appears to be entirely absent from the Americas and Western Europe. It survived the decline of the 1970s in Russia, China, and the formerly Communist states of eastern Europe, and as Soviet communism fell and the Chinese economy grew in the 1990s it emerged from the shadows to supply the audio market. These count among them factories that have been in the tube business for a very long time indeed, and their products have many proven decades of reliable service.

So if you buy a tube with a Western sounding brand name today it will have been made in the same Eastern factories as those with an obviously Communist heritage, and thus given that the same part numbers are available from the same sources under those cheaper brands it’s difficult not to wonder whether or not they are in fact exactly the same tubes but with an inflated price.

Communism, Folks, The Secret To High-End Audio

JJ’s take on the KT88 power beam pentode.

In the Slovak Republic are JJ, a very long-established tube manufacturer who were previously the consumer end of the Tesla vacuum device range. They don’t admit to branding their tubes for anyone else on their website, but they are reputed to be the source of those Telefunken-branded parts. Moving eastwards to Russia we then find SED-SPb in St. Petersburg, for whom consumer tubes are listed on the website as a small part of their range alongside industrial and high-power RF vacuum devices. They were previously the producers of the Svetlana range of tubes through the Soviet era, and though they no longer have that brand name they retain the winged C logo from that era. It’s unclear whether they are still involved in the production of branded tubes as their website is not very informative, but the “Winged C” tubes manufactured by them are still on sale.

Further across Russia in the southern Russian city of Saratov is the Expo-PUL factory, and here is where the story becomes interesting. It’s owned by the American Electro-Harmonix company, who in turn hold the rights for a host of older brands including Svetlana, Sovtec, Mullard, and Tung-Sol. It’s here that reissued Mullard ECC83 is made, and it has made the news in the past as Russian mobsters reportedly tried to seize it.

PSVane are definitely marketing their tubes such as this 300B as desirable high-end products.
PSVane are definitely marketing their tubes such as this 300B as desirable high-end products.

Into China, and the situation becomes rather opaque. China has a selection of larger manufacturers who produce tubes to a very high quality for the high-end export trade, but there are also inexpensive tubes on the market with scant manufacturer logos and little else in the way of traceability. If you pay $20 for an AliExpress tube headphone amplifier kit then it’s likely you’ll receive one of this latter variety, but its origins will be unclear.

The largest Chinese manufacturer is ShuGuang, based in Changsha, in Hunan province. They manufacture a large range as well as producing components for other brands. Their upstart competitor PSVane is also based in Changsha, and concentrates specifically on the high-end audio market. It’s unlikely for example that a 45 cent 6j1 small-signal pentode will have come from either of these two manufacturers or their smaller high-end competitors though, so it’s clear that there are more Chinese tube manufacturers at all levels of the market than can easily be found from the other side of the world.

Is It Really Worth It Though?

As someone who has been a vacuum technology enthusiast for four decades now it makes me happy to find that tubes are still in production and their industry appears healthy for now. But my tour through the world of 21st century tube manufacture leaves me slightly disappointed that so much of their marketing is still clouded by mythology.

As someone who was building tube amplifiers with Yugoslavian TV tubes back when it was extremely unfashionable, I understand the allure of that elusive “tube sound”, but experience has taught me that it’s not as great a thing as its proponents would have you believe. Even the distortion characteristics sought by musicians can more easily  be created through DSP in 2020, so I can’t help the feeling that people are being led astray as I see essentially the same tube being sold at a range of different prices based solely on its brand. Enjoy working with tubes, and enjoy listening to a tube amplifier. But don’t make the mistake of falling into the trap of falling for the hype, and never lose sight of the engineering.

92 thoughts on “Just Who Makes Tubes These Days?

  1. A set of electrodes in an evacuated glass envelope whose electrical properties depended on the modulation of the flow of electrons through them, these were ubiquitous in consumer electronics up until the 1960s, and clung on in a few mass-market applications even as far as the mid 1970s.

    You’re forgetting about one mass-market tube application that lasted quite a while longer: the cathode ray tube.

      1. Yep, although microwave oven vacuum tubes (magnetrons) aren’t as sexy since they lack the glass. Would still love to find a use for a salvaged one besides melting/destroying stuff. Maybe a massive Tesla coil or something…

        But then no discussion of modern day tubes should omit this French guy’s cool video of handcrafting vacuum tubes from scratch. Hackaday actually linked to it some time before. https://youtu.be/RKast1BZ_aE

        1. That sort of magnetron is not just a vacuum tube — it’s the entire transmitter. So it’s really difficult to repurpose it; even its transmitting frequency is not adjustable.

        2. Microwave glue curing is used in industry for wood bonding and composites, but I have yet to see an amateur use. I did see a magnetron weed killer. None of these of probably safe for the hobbyist though…

        1. the Korg Nutube is a triode instead of a VFD package, it isn’t a display it’s a teeny tiny amplifier. It’s probably a lot cheaper to manufacture than a traditional tube, and they could probably make a wide one and pack multiple tube elements in a single package.

  2. I didn’t really have anything else to say other than very nicely done. Just checking in.
    I noticed that in the referenced schematic from your Yugoslavian tube project the negative feedback is dependent on the resistance of the volume control wiper to ground and at high volume settings, input source impedance. Did you have any instability or distortion with low volume control settings?

          1. I find the comment section in HaD as informative and entertaining as the articles.

            Considering how important this is to the community, just pointing the finger to WP does not seem like something I’d be happy to read here.

            You are the paying customer. If the product, WP, does not work as intended. Have it fixed. If the supplier cannot, or is not interested in fixing it, it’s a big sea out there. Go fish!

  3. Wait… You said “Vacuum tubes”. You could have met us half way and called it a vacuum valve, to the confusion of everyone. I do think that “thermionic valve” is a better name in that it describes its operation a bit more appropriately. After all, it does control the flow of those mystical thermions.

    I do wonder how much longer some of the remaining tube manufacturers can stick around. The biggest market is almost definitely guitar amps, with the majority of all but the cheapest ones using them. Still, how many of those factories, especially in eastern Europe and Russia are using production equipment that is long in the tooth? I can perhaps see some of the Chinese companies keeping the ball rolling, and just maybe we might see a western company pop up to get in on the high-end action, but then that might be the final nail in the coffin for those ex-soviet manufacturers. Of course, I could be wrong and they could all be modern factories, but I doubt it.

      1. Because everything is ultimately a consumable, even machines. If the money isn’t there to reinvest in your manufacturing equipment, at some point the quality of your product will become unacceptable. I don’t know if that’s the case with any of them, and I have grossly underestimated JJ who, according to wikipedia, has an almost 1:2 net to gross income ratio with the latter being roughly $10M in 2015.

    1. People can make tubes at home in a garage. As long as there’s demand, someone will probably keep making them, and as long as they stay somewhat cheap, aesthetics will
      be enough of a reason for people to want them.

      I’m a big fan of class D, so I’ve never actually owned a tube amp or anything else tubeful,
      but they look cool for sure.

      1. In fifty years of electronics, I reme!ber one article from about 1964 about a ham in South America who made his own tubes. I think just power tubes for transmitters. It required skill, but also design. He had to know how tubes worked enough to make them.

        I suspect in the very early days some may have made their own tubes, but I recall no mention of that.

        And yes the guy in Europe who made a video some years back.

        That indicates it’s not so easy, and probably enough effort required that for most it’s cheaper to buy than make.

        1. Yeah, it’s almost certainly cheaper to buy rather than make, but pretty much anything that can be made at home can be mass produced cheaply.

          It seems like scientific test equipment like atomic force microscopes are one of the last DIYable things that’s still expensive.

          1. There’s a French (I believe) guy out there that builds high quality audio tubes – getters and all. He even built some custom equipment to help with consistency. Material selection is also critical. There’s a lot of stuff to know in order to build ones that are good sounding and long-lasting.

    1. Reminds me oft Yaesu FT-101 / Sommerkamp FT-277.
      One of the best FET transistor RX / tube finals TX combo to this day.
      Much better on HF than that pesky FT-817/818 every Ham nowadays is so obsessed with.. 🙄
      Also, Zetagi from Italy was popular for making affordable CB/10m tube amplifiers.
      They used line-end tubes (right English term?) originally meant for CRT TVs.

      1. Called horizontal output or “sweep” tubes.
        I used to tease other engineers who had early desktop PCs that their computer depended on a vacuum tube and most didn’t flash on the fact that the display was a cathode ray tube.

      2. Fifty years ago people could only dream of things like the FT-817, though the FT-101 was available 49 years ago.

        Upconversion was barely a thing, synthesizers didn’t exist in ham radio, digital readout only existed on one rig (and a few home made rigs), lots of features were absent or onky available on the too end equioment.

        There were a handful of 6M SSB rigs, and one 2M SSB rig (though in the past). There were no rigs that did AM, SSB and FM. If you wanted more than 6M SSB, you’d have to start with an HF SSB rig like the FT-101, and add a bunch of transverters to get on the VHF and UHF bands. For most it meant a rack of equipment.

        And now you can get it all in one small portable package.

        1. “And now you can get it all in one small portable package.”

          Well, that’s the illusion I meant.
          The 817 can do a lot, but can’t do it “right”.
          Hams are obsessed with black, small things that have dozens of knobs.

          A matching term is
          “A blind faith in progress”. I think.
          Development can not only go fort, but also go backwards. People tend to forget that.
          It’s same with economy. This don’t go “up” forever.
          New≠Progress

          As someone who had been used both
          FT-277E and several 817 (original, ND models), I come to this conclusion:

          Sensitivity below 30MHz is not on par with the venerable FT-101 of the 1970s,
          which is highly modular and expandable (digital freq. reader can be attached to IF output, FSK possible etc).

          The tiny SMD filters and circuits of the 817 do not have the same parts quality of their “real” fullsize counterparts. Esp. coils and quarz filters need the correct physical dimensions (not SMD).

          Also, modern band-pass filters are not as good as
          preselectors. If you ever used a magnetic-loop wit a variable capacitor, you get what I mean.

          In reverse, higher frequency bands such as VHF/UHF bands, need smaller dimension parts with smaller distances between components.

          Using a sensitive shortwave radio with transverters gives better performance than a deaf VHF/UHF radio.

          Or just use a €150 SDR RX/TRX. It will run circles around the 817.

          No kidding, SDRs like the €5 RTL-based USB sticks are much better than the 817 on the reception side, IMHO.
          The whole super-het design is dated by now. In fact, FM, SSB and Superhet are the things that old hams can’t let go.

          Direct-Conversion receivers from the earliest days of radio are much more versatile than superhets, if a computer/SDR software comes into play. 🙂

  4. “But my tour through the world of 21st century tube manufacture leaves me slightly disappointed that so much of their marketing is still clouded by mythology.”

    Of course. You can’t market to audiophiles without mythology.

    Still, a very nicely done article – it’s interesting to see that there are so many sources for this.

  5. The reason there are so many ‘brands’ of tubes or valves is that it is easy to clean off the glass and print your own brand on them. There is in fact a company in Oxford shire that does exactly this.

  6. There are many Hammond and Leslie sets that live on in Church and they need service. 6AU6, 12AU&X7, 12BH7, 6X4, 6550. Some of the power tubes have been short lived duds. It’s a real gamble, gassy from bad seals at the pins. Metal shards inside too. This is the option to replace 40 or 50 year old tubes that have finally gone low emission. Come Sunday things need to work.

  7. WOW, any of you actually have an amplifier that uses tubes. Longevity aside your assumptions are misgivings. Yup they are expensive. As a collector of 6SN7 tubes I can attest. Ever hear the RCA 6SN7 grey glass or a Sylvania 2-3 hole bad boy? There isn’t a transistor around that compares and no cheap device is squeezing out what a 6CA7 can do. Useless article. As for the guy who uses class D power it is thin and lacks drive. But I suppose that contempt is more fashionable these days than understanding. If price is a factor maybe this is not for you. BTW The Telefunkens are extended voltage JJ EL34 tubes hand selected then cryotreated and inspected again with a 48 hour burn in. My Genelex KT77 tubes also come at a price 154.00 a quad but are also burned in and double inspected. Sounds like the studio. So yeah I guess all apples are the same?…..So here is a quiz question what is the difference between reissue Mullards and new Tung-Sol EL34 tubes?
    Just amazing…..

  8. I bought a military surplus TV-7 tube tester at a hamfest for about $50 back in the late 80s. Then the tube audio nutz started buying up everything with a tube in it, driving up the prices, and realized they needed tube testers, so they drove the price of those up, too. My TV-7 is now worth about $500. Woohoo!

    1. But sadly, when the value hits $1,000 your poor tube tester will be stuck in the garage under 4+ decades of typical garage accumulation of “junk” and dust :) Good luck excavating through all that.

      1. Your point is well taken. It’s actually on a shelf in my work room where I occasionally pull it out to test radio tubes. It probably gets used once each year. I’ll die someday, and my family will dispose of my stuff without knowing that it’s worth anything. Maybe I’ll donate it to the Milwaukee Makerspace before that happens.

        1. I gather some people like to arrange their tube tester like it was at a drugstore, to emulate that experience of taking the tubes to a drugstore to see if they were good.

          I remember one article in a hobby electronic magazine by a service technician listing ways that those drugstore tube testers could mislead the consumer. Not deliberately, but just people not knowing enough.

    2. Well, audiophiles do at least take care of their stuff. If hams go their hands on them, they’d be gone since many years.

      Amateur radio people (myself included) often get hyped by new technology and throw away their old stuff, just because it’s not “in” anymore.
      Except for a few nostalgics/gentlemen, like my father, most amateur radio people I encounter are rather ungrateful, egoistic and greedy.
      (Young or mentally fresh hams of any age excluded ; some good souls with ideals and ham spirit are still out there and/or newly join the ham service from time to time. )

      Hams are like modern model train people, buying only the best stuff they can have, and blow their nose about old, handmade stuff that once was made with love and innocence. Even more so, they seem to be unfaithful to their inner child / to the person they used to be. They throw out stuff that their younger self put so much work into.
      Just because they can buy something “better’.

      That breaks my heart every time, because it’s not only false (got some old DIY hammcomm modems and rtty filters that work better in noisy situations than soundcard solutions!) but also is a hit in the face of ham spirit. We used to use our phantasy and imagination; now we sell our souls (not just rent them) for commercial stuff.
      Simply put, we turn into dull consumers on our free will. And like it, which is even worse, IMHO.

      Speaking of homebrewing/diy, It’s not like it used to be in the 50s, were Grandpa and Grand Son built their stuff together out of used cardboard, some wood, metal cans and old paint and had fun. Such craftsmanship is not absolutely gone, but rare. Now they use $1000 equipment (lathe, circular saw, 3d printer, cnc machine)..

      They dump venerable gear, make fun of it or sell it totally overpriced to some poor souls while patting their selves on the shoulders for being so clever and sly. Of course, after the gear had been tinkered with (ugly switches installed, lots of holes in the chassis, device inoperable). We are like used car sellers, I guess.

      Anyway, I’m glad that I haven’t participated on US ham fairs.. It was said that they once smashed old radios, mainly tube radios at the beginning of the solid-state graze, just for fun or burning them for a laugh. Eww.

    3. I don’t need a tube tester any more than I needed a curve tracer to find a bad transistor. I find it useful to use metal oxide resistors in plate and screen circuits, as they burn open sparing an expensive transformer. The open resistors tattle on the offending output tube, so I don’t need to witness the glowing plate. Someone gave me a tester decades ago, but I’ve never fired it up. Tubes are actually pretty forgiving. I remember learning that silicon virtually last forever, but decent tubes last longer than most people keep modern electronic devices.

      1. So there are levels here. Tube testers can be used as a pass fail for tubes and in fact back in the day there were a bunch of TV “technicians” who didn’t know anything about electronics who would go around with a tube tester as a method of up selling.. i.e., “see: the reading is at the lower green area, so we probably should replace this tube (ka-ching)”.
        The use of a tube tester other than crude trouble shooting is for push pull class AB1 to match 2 output tubes for gain and to reduce the second harmonic distortion in the PA stage.

        1. By the way. In broadcast applications where you might have a tube that costs $8,000+, they make a really big deal about filament and cathode temperature control. The filaments and cathodes are thoriated which makes them more electrically active (details omitted for brevity) meaning that the more intact the coating, the higher the gain. There is a depletion of this with time and temperature, resulting in eventual loss of gain. Broadcast tubes hardly ever fail, they just Peter out.
          So the method of control of this is to (after a 1 week burn in period) operate the filament at normal voltage while monitoring the plate output *gain*. Gradually decrease the filament power until you see a slight decrease in gain and nudge the filament power back up to recapture this slight loss. This minimizes the filament and cathode temperature (they are additive due to cathode resistance heating)
          You can typically extend the life of a tube from the typical 1 to 2 years to 4 or 5. Although it is more difficult to do with a Fender twin, the same would apply to well made small power output tubes. There is a lot to be said for regulated filament supplies. Also. The primary reason light bulbs and tube filaments burn out is because they have very low resistance when cold which creates a high in rush current when they are first turned on. You can significantly increase the life of tubes by limiting the initial cold filament current. I see some of the boutique guitar amp manufacturers are doing this with stepped filament voltages.

  9. I have a collection of 400+ tubes which I keep mainly for the pretty. Years ago I got a set of instructions for a DIY regenerative receiver that had been published in Boys Life in the1930’s, and I built it with a Type 30 from my collection. I should probably write it up sometime.

  10. I see that there are still many surplus NOS Soviet miniature tubes often selling for $2 each or less, even with shipping. We should be designing some audio gear using these still plentiful mil-surplus tubes, rather than chasing overpriced reissues of once-common tubes (looking at you 12AX7)

    1. Eh, those stocks will not last forever. If you use them in a mass produced thing, you get a mass market for replacements of that type, and eventually the thing becomes useless because there are no replacement tubes available anymore.

    1. I would expect there to be a premium price, but not *that* much for a power triode. Worse still is that the 300B appears to be the only tube they produce, so if you want a tube pre you’ll have to find some tubes as NOS, or if you’re using 12AX7s then maybe some cheap Russian or Chinese parts.. What a great way to compliment your $700 power tube.

  11. I forgot to mention that the amp in the story picture is an abomination. What possesses people to add LED’s to tubes and VF displays where they don’t belong. Showing my age perhaps..

  12. You’re missing one point in this discussion, circuit design at 500V separates the men from the boys. Plus it’s a lot of fun taking a free box of garage sale tubes, some wire, some iron, a little physics then making something like they did 100 years ago.

      1. Do you happen to have info on which caps they were? I have some GM-70 triodes and they get happy at about a kilovolt B+ so a cap suitable/reliable enough for a defibrilator sounds like a decent investment

    1. It’s hard to understate the importance of semiconductors in active electronics and the impressive amount of material science required to make them possible, but I’m with you. There’s something almost magical about elementary particles such as electrons moving around and being controlled in free space to do something so useful as amplify signals, or even draw images on a display.

  13. It is pretty compelling. I still have a Graymark 511 multiband tube regenerative radio I built in highschool, And I built a decent regenerative radio from scratch using a Russian equivalent of a 6SN7 dual triode.

    Regens are the haiku of radio design. So much going on with so few components.

    1. If we’re going there, we could include particle accelerators. And with THAT, I recall that there were some magnetrons way back in the day, called cyclotron magnetrons, which used different strapping between the cavities that made them operate similar to cyclotrons.

    2. That’s a good point.

      There was a slow shift to non-tubes for things that were the holdouts for tubes.

      People have already mentioned CRTs here. I recall some replacement for geiger tubes, but I can’t remember how direct a replacement they were.

      Have no idea about xray tubes.

      Microwave ovens surely still use a tube because of the power needed. It’s worth keeping making those tubes because they do it so well.

  14. I like articles such as this because it really puts things in perspective…

    I suppose it’s time to pull the tubes out of my ‘Atwater-Kent 60’ and the cathedral-style ‘Lyric Superheterodyne Model S-7’ and sell them. The tubes are probably worth far, far more than the intact, complete radios.

    Also probably time to cash out my ‘Technical Series RC-21’ RCA receiving tube manual (which contains the world’s BEST tutorial on vacuum tubes, lots of applications circuits–my favorite is a 50-watt hi-fi stereo amplifier–with full details, and complete details on building a tube-tester). Price on the cover? $1.00.

    Keep stuff like this coming; I never considered the fact that just one of my “All-American-5” ac-dc superhets (plans ALSO in the RCA tube manual) would pay next month’s rent.

  15. I once heard a home made Stereo Amplifier using Millard Valves connected to a CD Player , it produced a wonderful warm sound from the Amplifier and clinically Sound from CD Player, it was a wonderful combination of old and new Technology , Millard Audio Valves were famous for Reliability and quality a long time ago used to be owned by Philips, Ross

  16. I wonder if there are still TV stations out there using transmitters with a tube for the final stage? There is an excellent video on YouTube showing an electronics nerd getting a tour of an old analog TV transmitter (one that had been replaced by a digital transmitter) and it had a massive tube as the output stage amp for the video signal.

    1. I haven’t done a comprehensive manufacturer search but my general sense is that the DTV transition which has a much lower power requirement and uses significant digital pre distortion may have replaced most of not all of the tube based TV transmitters.
      Those were something to behold. UHF Klystrodes mounted in a 6 foot tall wheeled metal frame with liquid cooling hoses coming out the sides and a corrugated ceramic insulator on the bottom where you supply -23,000 VDC at 4 amps.
      Extremely high gain and very linear. 15 watts from the exciter yields about 40 KW before the diplexer. So linear you could do “IF duplexing” and transmit aural and visual carriers on a single tube. Many transmitters had 2 identical cabinets with capabilities of running aural in one cabinet and visual in the other or if diplexing at reduced power while pulling maintenance on the other cabinet. It’s been a while but last time I priced one of these tubes they were north of 30 grand each and it took 3.
      2 in cabinet and 1 spare.
      Typical sizes 30 60 120 KW RF.
      You needed to be really careful pulling maintenance.

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