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Using big RF tubes as audio amplifiers
OK, I just had to ask this. Has anyone ever tried using big glass RF
amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? |
#2
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On 12 Apr 2005 10:17:31 -0700, "Billy Boy (78's Rule!)"
wrote: OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? Sure you can use it as an an audio power amp. Interesting set of design challenges though. Anode voltage around 3000 and a current of 300mA. You will need a good output transformer. You will also need a high power (25 watts) driver stage to feed it. d Pearce Consulting http://www.pearce.uk.com |
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Thanks for the interesting reply, Don. Have you ever seen a pair of
3-500Z's in service in a Heathkit SB-220 RF amp? I feel that Heath proved in the '220 that with proper design techniques, the power supply need not cost an arm and a leg. But tell me this: would it require a special audio transformer in order for its primary to avoid breakdown at 3000VDC, since obviously that primary is going to be in the plate circuit? I would like to build an audio amp like that someday, just for fun. I've had Peter Dahl build special transformers for me in the past. They aren't that terribly expensive. |
#4
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"Billy Boy (78's Rule!)" wrote in message oups.com... : Thanks for the interesting reply, Don. Have you ever seen a pair of : 3-500Z's in service in a Heathkit SB-220 RF amp? I feel that Heath : proved in the '220 that with proper design techniques, the power supply : need not cost an arm and a leg. But tell me this: would it require a : special audio transformer in order for its primary to avoid breakdown : at 3000VDC, since obviously that primary is going to be in the plate : circuit? I would like to build an audio amp like that someday, just : for fun. I've had Peter Dahl build special transformers for me in the : past. They aren't that terribly expensive. : You need _special_ everything ! That is special wiring, sockets, transformer, power supply capacitors, even resistors .. and forced air cooling and a hefty filament supply. Did i mention the voltages in the circuit are absolutely deadly ? It would be a DIY project in the same sense as making nitroglycerin in your home lab - unless you've worked with 'lesser evils', a lot, *and* know what you're doing, don't even think about it ! Fun is fun, but dead is dead Rudy |
#5
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Oh, yes, I've built high-power RF amps before. Right now I'm using an
SB-220 in my amateur station. Those 3-500-Z's are such IMRESSIVE-looking tubes! But thanks for the warning. |
#6
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"Billy Boy (78's Rule!)" wrote in message oups.com... : Oh, yes, I've built high-power RF amps before. Right now I'm using an : SB-220 in my amateur station. Those 3-500-Z's are such : IMRESSIVE-looking tubes! But thanks for the warning. ...i found myself speeding through the Ardennes one night, 100 mph or so, at the wheel an ex-cab driver. he thought it more fun, to do that without the headlights on.. ...guess he knew what he was doing :-) Rudy : |
#7
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"Billy Boy (78's Rule!)" wrote in message oups.com... OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? Glass Audio 1997 (Volume 9, #1) had an article by Michael Burrows detailing the contruction of a PP amplifier around the 4-250A beam tetrode by Eimac. It looked to be quite a beast, ~ 150+ wpc. Great article, lots of detail. You can get the CD ROM of 1997 GA for ~$20 from www.audioxpress.com if your interested. The OPT was sourced from Audio Electronic Supply. I'm pretty sure its still available. Mark |
#8
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Hi, Mark, and thanks for the info on audioxpress.com. I will check it
out. I looked up the 4-250A because I hadn't seen one in a long time. The Eimac spec sheets do list it in audio amp service A pair of them is rated at 1040 watts max output in class AB2 with 3 KV on the plates, but the THD figure is 4.5%. My two present power amps are rated at ..01-.1% and .2%, respectively. The lowest THD figure for the 4-250 is 2% with 2500 plate volts in class AB1. A pair of 3-500Z's is rated at 1,420 watts max output in class AB2 audio amp service, but the Eimac sheet doesn't list its THD figures as an audio amp. I dunno, those THD figures don't seem so great to me; what do you think? In the meantime, I am going to see if I can get a copy of the article you're referring to. Thanks again. Bill |
#9
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Hey Billy Boy,
I have a couple of pieces of test gear that I do not know the purpose fo that use QE08/200,aka7378.The things have a OPT that will work at 8 ohms.They seem to be a pretty typical PP circuit with neg and pos feedback adjustments.They seem to be some kind of high current signal generator.The controls seem to indicate audio spectrum use. What a couple of beasts! I can barely get one on the bench.I have looked at the tube spec's and they do call out for audio.They call for 750 volts. That seems in the realm of sanity.But I am not going to mess with them untill I grow up.They are just so massive they scare me a little bit.The OPT's are huge as well as the PTs and chokes.I need a spare as one of mine is gassey. I see them for sale online now and then.But the places that a search turns up want way to much for them. Anyway you might look at these as a big tube project.There might be others that do not require as high as a voltage as the ones you mention but I think the big power ham tubes generaly require the frankenamp type power supplies. Just rambling.I really am just a newbie tube freak.But it would be cool to have a massive tube amp without eight 6550's or some such thing. WesJ....... "Billy Boy (78's Rule!)" wrote in message oups.com... Hi, Mark, and thanks for the info on audioxpress.com. I will check it out. I looked up the 4-250A because I hadn't seen one in a long time. The Eimac spec sheets do list it in audio amp service A pair of them is rated at 1040 watts max output in class AB2 with 3 KV on the plates, but the THD figure is 4.5%. My two present power amps are rated at .01-.1% and .2%, respectively. The lowest THD figure for the 4-250 is 2% with 2500 plate volts in class AB1. A pair of 3-500Z's is rated at 1,420 watts max output in class AB2 audio amp service, but the Eimac sheet doesn't list its THD figures as an audio amp. I dunno, those THD figures don't seem so great to me; what do you think? In the meantime, I am going to see if I can get a copy of the article you're referring to. Thanks again. Bill |
#10
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Billy Boy (78's Rule!) wrote:
OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? 3-500Z is no good. Theres plenty of people using 833As or rare 212s. By far the most popular is the russian GM70. Its cheap and seems to perform well. High mu transmitting tubes and class A2 are a good mix. Adam |
#11
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Heathkit kinda proved you don't need a huge, really stiff plate supply
for these tubes, as long as you have plenty of capacitance in the filter. You can use a voltage-doubler supply and the huge charge stored in the filter will carry the amp along. When I was 14 years old, I built my first kilowatt RF amp, and accidentally took the 3KV across my arms (I thought for SURE that center-tap wasn't grounded!). I was lucky that my muscular contraction made me throw the wire away (otherwise I think I would have been killed for sure), but it pulled an arc to the tip of my right index finger as it flew off, and burned the tip of my finger off (it healed fine). But I learned my lesson about being careful around HV B+ supplies. |
#12
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#13
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"Billy Boy (78's Rule!)" wrote in message oups.com... Hi, Mark, and thanks for the info on audioxpress.com. I will check it out. I looked up the 4-250A because I hadn't seen one in a long time. The Eimac spec sheets do list it in audio amp service A pair of them is rated at 1040 watts max output in class AB2 with 3 KV on the plates, but the THD figure is 4.5%. My two present power amps are rated at .01-.1% and .2%, respectively. The lowest THD figure for the 4-250 is 2% with 2500 plate volts in class AB1. A pair of 3-500Z's is rated at 1,420 watts max output in class AB2 audio amp service, but the Eimac sheet doesn't list its THD figures as an audio amp. I dunno, those THD figures don't seem so great to me; what do you think? In the meantime, I am going to see if I can get a copy of the article you're referring to. Thanks again. Bill Bill, I think most any transmitting tetrodes will require generous NFB to get decent distortion figures, especially AB2 operation. Maybe the transmitting triodes would be better from that stand point but then you'll need quite the driver stage for those guys. I admit, building an amp with these type tubes is something I've given thought to. I always thought an 813 would be a good tube to start with, work out the bugs with the $50 Chinese tubes then spring for some NOS when ready. NOS would probably out live me under audio conditions. Mark |
#14
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"Billy Boy (78's Rule!)" wrote in
oups.com: OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? I have built a guitar amp using an ABB T-1000 which is a radiation cooled glass job. About 1200 watts plate diss. I had an eimac 3-1000 to choose from and also a similar EEV and the French one (forgot the brand) but the ABB has a neat looking graphite anode so this was the choice. I have these available where I work, I would not consider buying one. Topology is single ended class A. Transformer I wound myself on a large C-core. It has an airgap and is interleaved. 3db response is about 40 Hz to 30 kHz. In hindsight I might not interleave a guitar amp tranny since a had to roll the highs off anyway. Filament is running 8V at 22 amps DC. B+ is 700V and output power is 60 watts. That is plenty for a guitar amp. Was fun to bulid and use, took about 10 nights to make but the outer box is not finished yet. I had a piece of Pyrex bent up to put in front on display. A couple of pics are at webshots.com, just search using "triode" and "single ended" I think. I think you can get reasonable RF tubes from places that make furniture out of ply, they are used for dielectric heating and at lower B+ than this app, they may work. |
#15
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Ruud Broens wrote:
It would be a DIY project in the same sense as making nitroglycerin in your home lab - unless you've worked with 'lesser evils', a lot, *and* know what you're doing, don't even think about it ! I don't know about making 'making nitroglycerin in your home lab' because, since I owned the entire computer installed at the university, I didn't have a lab at work and at my racing team we weren't fancy enough to call the workshop or the dyno room a 'laboratory'; once, when I referred to the engine assembly space as "the clean room", one of my mechanics whispered to another one, "He isn't queer, is he?" But I do have experience of making DIY nitroglycerine. My brother, Bullseye Johnny, was given the contract for killng all the crocodiles on the Oubangui River by Moise Tsombe in return for a favour (the favour was not shoving his rifle up Tsombe's arse for Moise being rude to the wife of one of Johnny's men--Moise also gave Johnny's askari a little baggie of diamonds to sooth his wounded pride; Moise didn't think it was funny when I remarked that he put rather a high price on his arse). Some Chinese, who lost face when they tried not to pay a gambling debt to "a student" and I then turned up with enough force to make them pay, and for wasting my time made them kneel in dog**** in the street while their customers watched and I read a poem I had written (the poem was about how their dicks were smaller than their skill at cards), had put a price on my head. So in the college vac, while it all blew over, I went with Johnny to shoot a few crocodiles. It turned out there were 1.2m crocs; the reason they had to be removed was that they were eating quite a few people. It was impossible to shoot them all. By the end of the second day our hands were so swollen from firing rifles it was impossible to carry on. We had some sticks of dynamite though. The problem with dynamite is that it is slow to work with and not all that explosive; the upside is that it is safe if you keep it cool. I got the idea of the nitroglycerine from wiping down a stick of sweating dynamite and flicking the sweat beads, nitro, from my fingers agains a treetrunk, which suddenly went missing, with this huge bloody tree toppling over on us. I immediately sent all our 30 trucks to the capital to fetch more dynamite, since we had only a couple of cases for blowing up big rocks on the road and blasting highwaymen's houses if they held us up unreasonably on the road. (Unreasonably is defined as pointing a firearm at us or any of our men, or trying to negotiate the toll on the road longer than ten minutes, or touching any of the women in the party.) DIY NITROGLYCERINE FROM STICK DYNAMITE: Build a fire with hardwood that will make coals or start with charcoal. Arrange several sticks of dynamite in a frying pan, not too tightly. Place on coals. Don't worry, it won't blow up while it is still dynamite. The nitroglycerine sweats out and runs around in the bottom of the pan. Carefully pour off the nitroglycerine into a mason jar (like your granny used for fruit preserves), making sure to fill level to the top so there is no slosh room or there won't be enough of you left to slosh in a doggie baggie. When the jar is full put on two or three sealing rings (for bump isolation when you screw on the top), screw on top carefully. Do not bump this bottle or the frying pan. (OPTIONAL) KILLING CROCODILES WITH YOUR BOTTLES OF NITROGLYCERINE Put a dozen halfpound bottles (halfpound contents; the glass weighs more) in the bottom of the boat. Carefully tie together with string. It helps to pre-knot the string to the desired interval between bottle so you aren't dropping loops of string on the bottles while you stand around measuring. Scull gently across river. Try not to hit anything. On the way back to whichever side of the river your camp is on (we made camp both sides of the river in case someone should have an accident with the nitro) gently lower your bottles of nitro into the river. Remove your boat from the river. Stand well back and throw a log into the river. Catch a big bath. Next day pick up your dead crocodiles downriver, their skins beautifully preserved and whole. The are killed by the compression of the water. Do only one or two rows of fruitjars across the river at a time, about a hundred feet apart. On our first try we laid eight lines across along about a kilometre of river and the resulting tsunami swept away two of our trucks that were parked a hundred paces onto dry land. I crawled out of the river eight miles down with a live croc snapping at my heels and I can tell you it was long, lonely crawl back to our camp with pygmies hunting me (blowtorch poison darts, you suffocate terminally in eight minutes) and black treesnakes hanging down to inspect my nose (no antidote to its bite, you suffocate terminally in four minutes). Talk of adventure holidays! RECIPE FOR CROCODILE EGGS We eat all kinds of eggs of course, from chicken and other birds, fish (caviar, roe), and so on. Most of the rarer eggs are too rich for most people's bland taste. Ostrich and crocodile eggs need to be diluted with milk to make them palatable. Ostricheo have six-inch long forward-facing nails and will of course kick you to death for stealing their eggs; nasty brutes, ostriches; I used to ride the big males in races and we kept an ambulance on standby because it wasn't advisable to fall off; one poor bugger got ripped from his sternum to under his chin: I scooped his guts and other organs back into his stomach with my hands and the surgeons sewed him together so neatly we nicknamed him "The Zipper". Crocodile eggs are buried in mud or on sandy banks beside rivers. Unfortunately, crocodiles are good mothers. You need to be nimble to collect enough crocodile eggs for breakfast for a large party. All four the cooks on the crocodile expedition had scars on their legs. Collecting crocodile eggs is not like going to the market garden... I hope this information helps, Rudy. If you have children and you want to keep them, you should of course not show them this message, nor give them enough pocket money to buy dynamite. Andre Jute PS I related the experience at greater length in a book under a pseudonym: African Revenge by Andrew McCoy, published by Secker & Warburg, London about 25 years or so ago, also in several paperback editions and translations. John Braine, a novelist I have always admired, wrote in his review of African Revenge in The Telegraph, "He goes places where no sane man goes except in divisional strength and with air cover." I thought at the time, It wasn't *that* dangerous. (1) Wouldn't do it today though; learned my lesson; do something safe and responsible instead: I build kilovolt amps. (1) It is true there were rather a large number of people trying to take the crocodile skins from us, and they were all armed and short-tempered and very trigger-happy and given to ambushes, which ****ed my brother off, and since he earned his nickname by shooting first and asking no questions, not too many of them survived their greed. Johnny's askari, who were Swahili from the other side of the continent, were of the opinion we should have let the crocodiles eat them. Still, it probably wasn't as dangerous as going to Denver to buy tubes for your geetah amp... Ruud Broens wrote: "Billy Boy (78's Rule!)" wrote in message oups.com... : Thanks for the interesting reply, Don. Have you ever seen a pair of : 3-500Z's in service in a Heathkit SB-220 RF amp? I feel that Heath : proved in the '220 that with proper design techniques, the power supply : need not cost an arm and a leg. But tell me this: would it require a : special audio transformer in order for its primary to avoid breakdown : at 3000VDC, since obviously that primary is going to be in the plate : circuit? I would like to build an audio amp like that someday, just : for fun. I've had Peter Dahl build special transformers for me in the : past. They aren't that terribly expensive. : You need _special_ everything ! That is special wiring, sockets, transformer, power supply capacitors, even resistors .. and forced air cooling and a hefty filament supply. Did i mention the voltages in the circuit are absolutely deadly ? It would be a DIY project in the same sense as making nitroglycerin in your home lab - unless you've worked with 'lesser evils', a lot, *and* know what you're doing, don't even think about it ! Fun is fun, but dead is dead Rudy |
#16
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Daddy not pay enough attention to you when you were young?
Adam |
#17
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Billy Boy (78's Rule!) wrote:
OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? What I was wondering is--would it be possible to use two television picture tubes as audio amps? What makes me wonder this is that I can hear sounds as my computer monitors turn off and on, from the picture tubes. High-pitched sweeps falling down; which leads me to think that they could give off sounds directly, if fed audio signals. So would you even need speakers? Wouldn't be hi-fi I'd guess, but still. It would be pretty interesting to see/hear,,,,, |
#18
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Dear Doug: Your hearing must be slightly deteriorated. If you could
hear better, you would hear your computer monitor talking to you at this very moment, saying, "It's not nice to post sarcastic replies to Billy Boy's posts." I would rather use one impressive-looking tube than all the nondescript output tubes they use on OTL amps. I think I can hear sounds from the picture tubes. High-pitched sweeps falling down; which leads me to think that they could give off sounds directly, if fed audio signals. |
#19
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DougC wrote: Billy Boy (78's Rule!) wrote: OK, I just had to ask this. Has anyone ever tried using big glass RF amplifier tubes as audio amps? Maybe a tube such as the 3-500Z, which is rated at about 500 watts of plate dissipation? What I was wondering is--would it be possible to use two television picture tubes as audio amps? What makes me wonder this is that I can hear sounds as my computer monitors turn off and on, from the picture tubes. High-pitched sweeps falling down; which leads me to think that they could give off sounds directly, if fed audio signals. So would you even need speakers? Wouldn't be hi-fi I'd guess, but still. It would be pretty interesting to see/hear,,,,, Well no doubt a picture tube could operate as a triode amplifier. And maybe give some weird wacky colour effects as well. I know a guy who has synethesis, ie, his senses cross over a bit, and not only does he hear what comes from his fab hi-hi system, but he sees colours coming from the speakers as well. Some ppl find light changes make sound they can hear. So speakers that lit up in all sorts of strange ways but in time with the music might be interesting. Its been attempted before though...... Patrick Turner. |
#20
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"Billy Boy (78's Rule!)" wrote: Dear Doug: Your hearing must be slightly deteriorated. If you could hear better, you would hear your computer monitor talking to you at this very moment, saying, "It's not nice to post sarcastic replies to Billy Boy's posts." I would rather use one impressive-looking tube than all the nondescript output tubes they use on OTL amps. I think I can hear sounds from the picture tubes. High-pitched sweeps falling down; which leads me to think that they could give off sounds directly, if fed audio signals. The only high pitched sweep I have ever heard fall down was when Kylie came around to sweep my chimney. Some how she lost her footing half way down, and fell to to the hearth in a cloud of dense black soot, " SSSHHHeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeTTT!" she screemed in a high piched tone. She went in as a blonde, and came out a changed woman. But I sorted her out in the shower, scrubba dub rub....... Patrick Turner. |
#21
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It seems You are aiming at The Final Single-Ended Triode. There are
metal/ceramic ones, but they do not glow, therefore 50% of the magic gets lost. There are "customary" big ones (211, 845, 813, GM-70 etc.), but it seems You want something really weird, and this could lead to some disappointment because large transmitting tubes are not necessarily good sounding, since linearity was not required for their intended purpose. Among the glass monsters I saw used for their SET amps by some senior-league weirdos, there's the 833A (still produced in Ukraine as GU-48 and available at fair prices), the Russian GM-100 and the terribly expensive 4212. Somebody managed to get FOUR (yes, to have spares) former Royal Navy STC 4212 to make a 100W SE, but I suppose I'd be kicked out of my home's door if I blew 4 or 5 kilo-euros in tubes. There are many others big radio bottles, say 100TH or the "800" series ones (805, 809, 810...), but most of these are still in the 100 - 150W range, therefore they have no advantage over the GM-70 (125W). Problems (apart from electrocution-related risks): - power consumption/heat/weight (the filament of a GM-100 takes 300W just to light up!): better make the whole amp as a series of modules to be installed in a fixed HV cabinet or to provide wheels to move it from the lab to the listening room (my wife wouldn't allow forklifts to run across the carpet..) - output transformer performances: it has to handle maybe 500mA DC at 2kV, this means A LOT of iron and copper. Getting a good bandwidth will be a pain in the bottom. - driver stage: when using radio tubes, positive grid is usual, which means that the driving stage needs to supply a substantial amount of current. Indeed, it must be a smaller power amp. Briefly: I suppose that the best is to use a couple of GM-70 (or 845) tubes in PP class AB1. This will provide more than 200W with a substantial amount of class A @ say 1% THD with NO overall feedback and NO DC thru the OPT. Furthermore, these tubes need a big driving voltage swing, but they do not need to be driven into positive grid and, as a safety bonus, they do not have unprotected anode caps. This way, it is feasible to make the best possible OPT and the best possible driving circuitry at a "viable" cost and to make a mono amp weigh less than 100# ... If the circuit is really good, I bet it is absolutely impossible to hear that it is not SE as long as it operates in class A (add a differential amp as a driving stage to make sure, see Williamson). Larger power (350-400W) can be obtained by using tetrodes in B class, say 813 or GK-71, but these will need a large amount of feedback. Ciao Fabio "Billy Boy (78's Rule!)" ha scritto nel messaggio ups.com... Dear Doug: Your hearing must be slightly deteriorated. If you could hear better, you would hear your computer monitor talking to you at this very moment, saying, "It's not nice to post sarcastic replies to Billy Boy's posts." I would rather use one impressive-looking tube than all the nondescript output tubes they use on OTL amps. I think I can hear sounds from the picture tubes. High-pitched sweeps falling down; which leads me to think that they could give off sounds directly, if fed audio signals. |
#22
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Patrick Turner wrote:
"Billy Boy + Patrick Turner.... Well I did not suppose it would sound GOOD, but that it "sound". -Would *be audible*. Tube-microphony? Tube-speakerphony? ----- Not loud enough for regular room-listening perhaps, but other possibilities. "Here, stick these in your ears and tell me how it sounds...." |
#23
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What is this piece of test gear?
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