11 ms·
The Vacuum Tube’s Forgotten Rival
- skeptikal 5y agoNo forgotten, but definitely hard to get info from. You can find some books on the internet archive. Subs use them, high T and rad places still use them (Im told).
- Aardwolf 5y ago"Amplification occurs because a relatively small DC control current can modify a much larger AC load current." Doesn't the larger AC load current itself also saturate the core though, overpowering whatever the much weaker current does? Or is only DC current able to saturate it?
- kragen 5y agoThat would be true at the same number of turns, but Ken explained that the control winding has more turns, in effect multiplying its current.
- Aardwolf 5y agoTo use them in a computer for logic gates, if you want to have multiple logic gates work together (such as an adder where bits propagate through many gates), does that then mean you'd need to convert AC outputs to DC control inputs for every single connection between gates? Or is there some more efficient way they did this?
- kragen 5y agoI think that is correct. But maybe you can use diode logic instead for most of your gates, resorting to ferrite only when you need inversion, amplification, or memory.
- kens 5y agoFor logic gates, the signals are pulses, so it doesn't really make sense to categorize them as AC or DC. If you want the exact circuit, take a look at the Univac Solid State manual page 6-89: http://www.bitsavers.org/pdf/univac/uss/UNIVAC_7900_Central_Processor_90_Theory_of_Operation_Service_Manual_No_1.pdf http://www.bitsavers.org/pdf/univac/uss/UNIVAC_7900_Central_...
- kragen 5y agoThank you! I've been looking for good info for years. You don't happen to know about Soviet ferrite/diode systems, do you?
- kens 5y agoSorry, no, I haven't come across any information on Soviet systems.
- kragen 5y agoApparently, due to lagging semiconductor fabrication technology, they were the state-of-the-art devices in the USSR even several years after losing to transistors in the US. I was terribly confused when I first heard about "ferrite-diode systems" since you obviously can't make a diode out of ferrite!
- taylodl 5y agoBut will it chug?
- tmountain 5y agoArticle seems to be behind a paywall.
- mtreis86 5y agoIf you close the popup window asking you to make an account the article is still there in full.
- sreevisakh 5y agoThat can't be. Spectrum articles usually aren't. I was able to read it in full by selecting 'Keep reading'.
- zmix 5y agoI could access the article fully from Germany.
- agumonkey 5y agojust in case, someone posted the wbm link http://web.archive.org/web/20220327154828/https://spectrum.ieee.org/the-vacuum-tubes-forgotten-rival http://web.archive.org/web/20220327154828/https://spectrum.i...
- nateburke 5y agoDoesn't a form of mag amp figure prominently in Gravity's Rainbow? https://niklasriewald.com/2020/01/02/the-math-behind-gravitys-rainbow-part3-double-integrals/comment-page-1/ https://niklasriewald.com/2020/01/02/the-math-behind-gravity...
- JKCalhoun 5y agoNo surprise ... Pynchon writing cyber-punk before cyber-punk. Solid-state-punk.
- 13of40 5y agoWhen I read the title, my first thought was about the cryotron: "Tantalum in superconducting state can carry large amount of current as compared to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire." https://en.wikipedia.org/wiki/Cryotron https://en.wikipedia.org/wiki/Cryotron
- kens 5y agoI actually mentioned the Cryotron in the original draft of this article, but there wasn't room for it. Some of the other forgotten computing technologies of the 1960s are tunnel diodes, microwave oscillators (Parametron), and electroluminescent photoconductors.
- stevespang 5y ago
- IndrekR 5y agoDid a design with a tunnel diode in 2011. Around 300 devices were made and sourcing the diodes was not easy — but still possible.
- ncmncm 5y agoCare to explain why a tunnel diode was the right thing for the purpose? And, if you had been unable to source them, what you would have done instead?
- IndrekR 5y agoIt was an experiment set for International Physics Olympiad. There was a black box with a tunnel diode, inductor and capacitor inside. If the diode would have been impossible to source, another set-up for the black box would have been used instead. Experiment is described here: http://hedgehog.ee/ipho http://hedgehog.ee/ipho
- neonate 5y agohttp://web.archive.org/web/20220327154828/https://spectrum.ieee.org/the-vacuum-tubes-forgotten-rival http://web.archive.org/web/20220327154828/https://spectrum.i...
- noipv4 5y agoI remember seeing mag amps in the computer PSU, back in early 2000s, before solid state regulators took over.
- krallja 5y ago> In the mid-1990s, the ATX standard for personal computers required a carefully regulated 3.3-volt power supply. It turned out that magnetic amplifiers were an inexpensive yet efficient way to control this voltage, making the mag amp a key part of most PC power supplies.
- myself248 5y agoForgotten? Every military vet I know who worked on electronics in any capacity, raves about the reliability and durability of mag-amps.
- dr_hooo 5y agoI for instance don't know any vets, so I learned something new from the post. So I'd say the title is fine.
- nobodyandproud 5y ago> “Many engineers are under the impression that the Germans invented the magnetic amplifier; actually it is an American invention. The Germans simply took our comparatively crude device, improved the efficiency and response time, reduced weight and bulk, broadened its field of application, and handed it back to us.” Quoting a quote: I found this quote of the 1951 US manual amusing.
- noja 5y ago"Many people forget that we invented the wheel. They simply changed the shape from square to circle, and changed the material from volcanic rock."
- jsnodlin 5y ago
- TedDoesntTalk 5y agoIt’s funny today. But to put it in context, many Americans wouldn’t use German products after the war. My parents refused to buy German cars and other items for decades. Much like Russian products are abhorred in America right now. Caviar, LukOil, Kaspersky AntiVirus, etc…
- mirceal 5y agoto be fair: german products are high quality when russian ones are of questionable quality
- TedDoesntTalk 5y agoSome are questionable, yes. But what about food, vodka, and gasoline, natural gas, and oil? I don’t think people avoided these products before the Ukraine invasion.
- bobthepanda 5y ago
- ililic 5y agoWhat is "alt-tech" ?? Is this a term used commonly? It's referenced in the subtitle but no where in the article.
- ILMostro7 5y agoPresumably refers to technology that was supplanted by an alternative technology or implementation for wider use. Inferred meaning, no sources to cite.
- Izkata 5y agoNot supplanted, but parallel evolution (theoretical or otherwise) that could have become the modern/main way of doing things. Compare to "alternate history" used in fiction.
- deleted 5y ago[deleted]
- jmbwell 5y agoAnd to this day, the representation of memory contents at the time of a kernel panic is called a "core dump."
- erosenbe0 5y agoAnother gem by Ken Shirriff! Master of deep-dives into semiconductor history.
- zw123456 5y agoThis reminded me very much of the old mag core memory from early days of computers https://en.wikipedia.org/wiki/Magnetic-core_memory https://en.wikipedia.org/wiki/Magnetic-core_memory
- krallja 5y ago> Researchers soon constructed what was called core memory from dense grids of magnetic cores. And these technologists soon switched from using wound-metal cores to cores made from ferrite, a ceramic material containing iron oxide. By the mid-1960s, ferrite cores were stamped out by the billions as manufacturing costs dropped to a fraction of a cent per core.
- nand4011 5y agoMy favorite anecdote about magnetic core memory comes from the development of the Naval Tactical Data System. https://ethw.org/First-Hand:The_Naval_Tactical_Data_System_in_Combat_-_Chapter_7_of_the_Story_of_the_Naval_Tactical_Data_System https://ethw.org/First-Hand:The_Naval_Tactical_Data_System_i... A paper bag of magnetic cores disappeared while the engineers were out to lunch: > But shortly after, the engineer called and asked if the shipment was there. This did not sound too good. With a little detective work we found a cleaning crew had worked in the office while we were gone. A little more sleuthing revealed that the bag had been accidentally knocked into a waste basket, and that load of waste had already been dumped into the plant incinerator. The incinerator ashes were spread over a concrete floor, and sure enough there were small magnetic cores, about one sixteenth of an inch in outside diameter, mixed in with the ashes. The CP-642 B had 32,768 30-bit words in its memory, meaning, with spares, there were just about one million magnetic cores in the ashes. At ten cents per core, the ashes held about one hundred thousand dollars worth of cores. We reasoned the cores were the result of a firing process, and the heat of the incinerator probably had not hurt them. Maybe it even made them better. A quick test of some of the cores picked from the ashes revealed the cores were as good as ever. We and a contingent of Univac engineers & technicians spent a fun filled day rescuing the cores from the ashes with long needles. The cores were strung into the machine’s memory planes, and it passed all performance and environmental tests with flying colors. That entire history is worth a read if you are interested in computer history of the military variety.
- 8bitsrule 5y agoThanks! I'd long wondered exactly how radio carriers were modulated before vacuum tubes. (Technical details of that era are often skimpy in histories.) This chronology of AM radio is interesting: [https://web.archive.org/web/20071118155548/http://members.aol.com/jeff560/chrono1.html https://web.archive.org/web/20071118155548/http://members.ao...] It mentions Fessenden's 1906 Xmas broadcast, and it looks like he'd just gotten one of Alexanderson's alternators. Paul Mali, Magnetic Amplifiers (1960;PDF) [https://web.archive.org/web/20061114175548/http://www.pmillett.com/Books/mag_amp.pdf https://web.archive.org/web/20061114175548/http://www.pmille...] Home-made MA's: [http://sparkbangbuzz.com/mag-amp/mag-amp.htm http://sparkbangbuzz.com/mag-amp/mag-amp.htm]
- myself248 5y agoYou can hear an Alexanderson live on the air, twice a year! https://alexander.n.se/en/the-radio-station-saq-grimeton/saq-transmissions/ https://alexander.n.se/en/the-radio-station-saq-grimeton/saq... Might want to get a head start on the receiving hardware, though. Most SDRs don't go that low, and though soundcards can go that high, their input impedance may not be well suited to whatever antenna you can cobble up. Oh, and you'll want an absolutely enormous antenna. Get a roll of cheap fence wire and string it halfway down the block...
- Johnythree 5y agoMany enthusiasts are using a tiny voltage probe antenna for VLF. https://www.on8im.be/en/active-antenna-pa0rdt.html https://www.on8im.be/en/active-antenna-pa0rdt.html
- neilv 5y ago> One Navy training manual of 1951 explained magnetic amplifiers in detail -- although with a defensive attitude about their history: "Many engineers are under the impression that the Germans invented the magnetic amplifier; actually it is an American invention. The Germans simply took our comparatively crude device, improved the efficiency and response time, reduced weight and bulk, broadened its field of application, and handed it back to us." Does that sound "defensive" to everyone? I don't know this area of engineering, so, to my ear, this could also plausibly be an almost admiring acknowledgement of someone else succeeding where you'd failed, combined (non-defensively) with confidence, because you had the strength or other superior merit to take it from them?
- ILMostro7 5y agoNot that it should matter, but considering the source (and time), the phrasing could be understood to imply a level of pride that we got there first. Although, they do seem to give the Germans credit for expanding the technology. Nevertheless, it's the reader that chooses how to interpret the text, and what lessons to learn from it.
- neilv 5y agoThat sounds plausible, too. Various nationalism and other thinking, in different groups, at different times, are still largely a mystery to me. It seems relevant to group thinking we see today, which is still confusing (e.g., why is much of the thinking and dialogue around the two main US political parties doing what it's doing, and how is that representative/determining of what the broader population actually thinks).
- ILMostro7 5y agoDivide and conquer approach of the populace, IMHO. From an international perspective, though, it may be useful to spur competition.
- throwaway73838 5y agoNo mention of musical applications. I’d be curious to hear what one sounded like.
- BizarroLand 5y agoMy guess is that they would sound close to transistors. I guess it depends on the tolerances though.
- strbean 5y agoI searched around for anything on audio mag amps and couldn't find any. Maybe we should build one and try it out?
- hilbert42 5y agoMagnetic amplifiers have been in use long past WWII, they were never obsoleted by War's end. For example, many stage lighting systems still use them. For example, the Sydney Opera House which opened in 1973 with the latest equipment used them for its stage lighting dimming (although they have now been replaced with solid state dimmers). Magnetic amplifiers are wonderful devices albeit a bit slow for some applications. Moreover, unlike SCR and other solid state switching, they produce no RF switching noise.
- c3534l 5y ago
- hilbert42 5y agoI did and always do. That ought to be obvious from my subsequent post.
- krallja 5y ago> In the 1920s, improvements in vacuum tubes made this combination of Alexanderson alternator and magnetic amplifier obsolete. This left the magnetic amplifier to play only minor roles, such as for light dimmers in theaters.
- hilbert42 5y agoVery true, but things get messy when one wants to dim/control say power at an mVA level and still do so at domestic mains voltage (in my example, the feed to the building is 3 mVA). At that power vacuum tubes require many kV anode voltage which isn't helpful when running loads that have to run at domestic mains voltage for safety reasons. Also with dimmer circuits one often has hundreds of channels, until solid state came along using vacuum tubes would have made the electronics very complicated not to mention highly inefficient. Another reason for using magnetic amplifiers is their utter reliability - they just don't fail (being so simple). In fact, they're still used in some industrial applications specifically for that reason (unlike the Alexanderson alternator which was a monster to operate and keep reliable - but then they each served different purposes). BTW, I'm not anti vacuum tube as for part of my career I worked with FM and TV transmitters. Even today, replacing, say, a 4CX10000D vacuum tube with a solid state equivalent is certainly no easy feat.
- erdos4d 5y agoI wonder how a Les Paul sounds through one.
- Lammy 5y ago"After the war, U.S. intelligence officers scoured Germany for useful scientific and technical information. Four hundred experts sifted through billions of pages of documents and shipped 3.5 million microfilmed pages back to the United States, along with almost 200 tonnes of German industrial equipment." Don't forget "and a bunch of actual Nazi scientists just for good measure" https://en.wikipedia.org/wiki/Operation_Paperclip#Key_recruits https://en.wikipedia.org/wiki/Operation_Paperclip#Key_recrui...
- guenthert 5y agoNo mentioning of EMP resistance? I thought there would be renewed interest.
- ncmncm 5y agoSomebody think of poor yttrium -- once the world's go-to source for electron-beam stimulated red dots of color TVs (although the red photons came, confusingly, out of europium instead) -- now languishing in relative obscurity, used mainly to make high-temperature superconductors, solid-state garnet lasers, and (with iridium and manganese) an intensely blue pigment. Or its cousins, ytterbium, terbium, and erbium, all of which were first refined out of an obscure mineral, ytterbite, and all named with a stunning deficit of creativity. Erbium has found a use, in picogram quantities, to amplify optical signals in fibers directly from exposure to light. Terbium was once used for the green dots on TV screens, but is still used in a material that expands and contracts in response to magnetic fields. Uses for ytterbium are more obscure. High-temperature superconductivity might be useful someday.
- deleted 5y ago[deleted]
- mikewarot 5y agoAn important transition is missed, that is that magnetic amplifiers are analog amplifiers. It was William Steagall of Sperry-Rand who realized that the flux saturation could be used as a digital logic element. If you send a pulse in the same direction as the core is already magnetized, you get no output pulse. From this, and a multi-phase clock to supply drive power, digital computing elements were created. https://en.wikipedia.org/wiki/Magnetic_logic https://en.wikipedia.org/wiki/Magnetic_logic
- mikewarot 5y agoAt the 6 Stand Cold reduction Mill of the US Steel, Gary Works, they needed a system to control the pairs of 9000 HP motors that drove the top and bottom rollers to stretch cold steel inches thick. Solid state electronics, and even tubes, weren't up to the task. Earl Pace was the Westinghouse engineer to figured out how to do it. He used a set of Synchronous AC motors to take the incoming 3 Phase, and drive a set of DC generators. The technology to control the field windings on the DC generators was just within reach. So he used the biggest SCR systems of the day to drive those. Driving the field windings allowed you to zero or even reverse the output of the generator. In effect, it was one of the largest magnetic amplifiers in history. Those generators then drove the DC motors on 6-stand. Some of the control circuitry used Magnetic amplifiers when they need to have multiple isolated inputs. The amazing thing is that they can pass DC signals to about 1 khz. (They had a 10 Khz drive signal) All of this from 1964. I repaired some of the control modules back in the 1980s, which is how I learned about it all.
- jacquesm 5y agoFascinating, thank you! Any pictures of the circuitry and the gear?
- mikewarot 5y agoUnfortunately, no. That was before my first digital camera. It was all Westinghouse controls in modules. There were many 3 phase SCR packs, good for about 100 AMPS each. I never got to see the motor generator sets.
- jacquesm 5y agoToo bad, I would have loved to see that stuff, it sounds super interesting. Thank you for answering.
- nonrandomstring 5y agoAt the height of early computing there were relays (Turing-Welchman Bombe) competing with vacuum-tubes (Manchester Mk1 etc), and all had MTBF times measured in hours. Constant replacement of valves and relays was a full time job. Why didn't magamps replace them? I don't think it was necessarily the efficiency, but the problem of doing logic using AC signals. Any EE's have thoughts on this?
- scns 5y agoWould like to know what they sound like when oversaturated.
- marcodiego 5y agoDon't know if it is oversaturated, but you can hear it here: https://youtu.be/DBX1-POuJMw?t=140 https://youtu.be/DBX1-POuJMw?t=140
- aj7 5y agoCuriously, the most important CURRENT application of magnetic amplifiers was not mentioned. In every excimer laser used for photolithography and thin film panel annealing, and possibly for LASIK, their is a multistage saturable inductor chain that compresses and amplifies the electrical pumping pulse generated by an IGBT or SCR switch. There are indeed few uses for this technology OTHER than the excimer laser.