Thread Number: 68679  /  Tag: Other Home Products or Autos
The "black beauty"capacitor phenomenon...
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Post# 914618   1/8/2017 at 12:32 (528 days old) by cfz2882 (Belle Fourche,SD)        

cruising around some of the vintage electronics forums,seems these 1950s era capacitors have long had a bad reputation for becoming unstable and lossy as they can absorb moisture despite the molded baklite casing.As problematic as these capacitors are reputed to be,they are highly prized by the guitar amp guys for the tonal characteristics they recon these capacitors have-even saying they have to be "broken in"with some usage before they sound "right" :) NOS and even salvaged "black beauties" can be found on Ebay.These are paper dielectric with molded case.

Post# 914625 , Reply# 1   1/8/2017 at 12:53 (528 days old) by rp2813 (The Big Blue Bubble)        

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Interesting.  Everything I've ever read about black beauties has described them as problematic and suggests they're the first place to look if there's trouble. 

Post# 914634 , Reply# 2   1/8/2017 at 13:13 (528 days old) by cfz2882 (Belle Fourche,SD)        

next time I have any of my 40s/50s electronics apart,i will look out for any bumblebees or black beautys :)I know I have some in my spares stash-will have to do some tests on those to see what happens.

Post# 914643 , Reply# 3   1/8/2017 at 13:54 (528 days old) by panthera (Rocky Mountains)        
I've got perfect pitch

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And I have to say - to my great regret, that the black beauty bombs do contribute to the sound.

Sadly, because their leakage also contributes to overheated plates and early tube death.

They explode, they catch on fire, they leak, yech.

Bumblebees should be replaced ruthlessly and without exception. They were trash when new.

Post# 914725 , Reply# 4   1/9/2017 at 01:06 (527 days old) by tolivac (greenville nc)        

Yes,I replaced caps like those in older amplifiers-Hi-Fi or G-Fiddle when they were old and leaky.Never had any of those explode-that is electrolytics and large oil filled caps that explode when faulted or shorted.The black caps were coupling caps-coupled the plate of one stage to the grid of the next.And yes the tell tale plate glowing of the output stage when the coupler caps get leaky-passing DC and putting a "false" bias on the next stage.In those cases-doesn't matter what kind or brand the coupler cap is-REPLACE IT!!Often have small oil filled couplers in AM transmitter modulator stages-same problems.Those couplers could have to block up to 6Kv!Have replaced the couplers in my "MAC" amps-but no HV caps available of the power supplies.While you are replacing the coupler caps-you may and should replace the bias rectifier diode as well.Often in those older electronics the bias diodes were selenium-these get weaker as they age-output voltage gets too low to properly bias the output stage.Do this as well when redoing older amps.

Post# 914757 , Reply# 5   1/9/2017 at 09:40 (527 days old) by panthera (Rocky Mountains)        

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You are so right - selenium used for any purpose is dangerous at this point. Just have to adjust for the different voltage drop between the nasty old and safer new diodes.


I've caused electrolytics to explode by putting them in the wrong 'way round. Sure I'm the only one to ever do so. 

Post# 914882 , Reply# 6   1/10/2017 at 03:08 (526 days old) by tolivac (greenville nc)        

While working in one of our transmitters today-we replaced a pulse step modulator module in our BBC 500Kw transmitter.PSM modulators are solid state-they use a triac like device-a GTO this handles 900V-1800V Pk at up to 60A.There are 32 of these modules in series to provide DC to the plate of the PA tube and modulation to it.The GTO is controlled by a circuit board-the board has a +- 15V supplies-the caps in this module were blown to bits-foil and fluff all over the board.So we figure both legs of the supply are trashed.The board is powered by a special step down transformer that takes 650VAC to 24V center tapped for the board supply.Now these moduls float at 12Kv above ground.The GTO device is powered by the secondary winding of the HV transformer-3Ph 650V.There are two transformers-16 isolated 3Ph windings on each.4160V 3Ph primary.Besids the PSM module there is a rectifier module for each mod module.3 fuses protect the rectifier boards.When those blow you check the diodes and surge diodes.If bad-replace them-then the 63A 700V fuses.Right now 3 of the modules oscillate-isolated them by pulling their fiber optic couples from the modulator driver boards.We have to rebuild the bad boards we pulled.Replace the GTO is the irst thing-they usually short.And those things are like $600 each!At this point like PP high level plate tubed modulators better!not so complex-less to blow.And the trouble above mainly caused by two 1000Uf 25VDC electrolytic caps!We are wondering the fun when the 3300 UF 350 VDC main filter caps in the rectifier boards go!They are 30 yrs old !!!Have strongly recommended these be replaced.I forget how many are in the transmitter-LOTS!!!!!!!
A charging circuit is in the rectifier board to limit current when the HV transformers are energized.Then a contactor bypasses the charging resistors.In some other transmitters I have worked on they had selenium rectifiers for the PA and mod bias stages.The transformers for these were multitapped to compensate for rectifier aging.Simply replaced the old selenium diodes with silicone ones-added like a 400 ohm surge resistor is series with the new diodes.Works much better!!!RCA "H" AM transmitters-5,10Kw.

Post# 914893 , Reply# 7   1/10/2017 at 05:10 (526 days old) by kb0nes (Burnsville, MN)        

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Indeed the old vintage components can and do have a different sound to them, the dialectric absorption isn't as well controlled as with modern parts so they are apt to cause their own distortions. It all depends on if said distortions are good or bad. We all likes what we likes in the end.

I'm a hifi fan, I believe in accuracy to the source and anything I can measure that is causing degradation has to go. I replace all the old coupling and bypass capacitors out of habit, modern plastic film capacitors are just better and more reliable. To a degree any amplifier I have worked on is "restomodded" even if just by the substitution of newer superior parts.

To a degree as soon as I hear people start talking about electronics "breaking in", I generally take such comments as crossing the line into psychoacoustic. In other words it is amazing what the mind can imagine. Breaking in cables or worrying if speaker cables lie on the floor vs being propped up on cute little stands. A lot of it comes down to the power of suggestion, if you think it makes a difference then when you listen it will. Boutique parts fall under this category, Audio specific capacitors that cost 100x more then similar commercial parts are just silly, but I suppose if you know they are in there then you will think it sounds better.

Guess I should start clipping out the Black Beauties with lots of lead length and put them out on eBay. My 1980 Marshall 2204 guitar amp still has all its original capacitors (course they are far more modern then Black Beauties) so I haven't messed with it. Well other then ditching the 6550 output tubes in favor of EL34's. I just didn't fancy the way the more modern HiFi tubes overloaded.

Post# 914970 , Reply# 8   1/10/2017 at 13:57 (526 days old) by firedome (Binghamton NY & Lake Champlain VT)        
Many a tube has red-plated...

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due to old leaky Bumblebees, always replace them. As to selenium rectifiers, in non-tube rectified electronics we always replace selenium with a 1N4007 silicon bridge, and as those give too much voltage add a 47 ohm 5 w resistor between the silicon bridge and the filter cap to drop the voltage to acceptable levels.

In the early 2000s we at VTV magazine did very extensive double blind testing with some notable engineers, designers, restorers, collectors &c in the Bay area of vintage HiFi and guitar amps with various and sundry types of caps for vintage HiFi and guitar tube amps. Conclusion: cheap Illinois metallized polystyrene jobs sounded every bit as good in vintage amps as "boutique" Auricaps and that expensive ilk. That's all we use in restoring any tube amp; we have H-K and Heathkit stereo tube units sitting on the bench as we speak.

The guitar guys can have their silly Bumblebees, they're the very same idiots that drove up prices of certain tubes to absolutely absurd levels. We sold them all our overpriced Telefunken and Mullards long ago, the old RCA, GE, and Sylvanias work just fine.
The audio snake oil salesmen are alive and well!

Post# 915051 , Reply# 9   1/11/2017 at 03:50 (525 days old) by tolivac (greenville nc)        

The Hi end Hi-Fi "Audiophools" are also responsible for the high prices on tubes and tubed amps.We can't put all the blame on the G-Fiddle guys.For some of those folks on both sides--I have a bridge for sale REAL cheap!!!Now the thing among audiophools is you must have a separate powerline feed for your system and premium grade outlets!

Post# 915053 , Reply# 10   1/11/2017 at 03:58 (525 days old) by tolivac (greenville nc)        

I have a high end Hi-Fi catalog that shows speaker cable supports-----Al they are are simply porcelion powerline insulators---just get friendly with any lineman-you may get some of those for free!Maybe the Hi-Fi guys should erect utility poles in their Hi-Fi room with crossarms and insulators!Oh No I am giving them ideas!You might see utility poles shown in that catalog!!!There was a video on YouTube or something that showed a Japanese Hi-Fi guy paying for a separate utility feed for his Hi-Fi equipment room-even with its own pole and "pole pig"!His wife insisted she couldn't hear any diffrences-but he insisted that he could!

Post# 915067 , Reply# 11   1/11/2017 at 07:10 (525 days old) by kenwashesmonday (Haledon, NJ)        

I believe that the only reason black beauty capacitors sound different is because they're leaky. A nice new Cornell Dubilier (formerly Sprague) "orange drop" capacitor will put the equipment back to factory sound and spec, no matter if it's in the amp on on the tone control inside the guitar. No need for expensive "boutique" capacitors, the only thing they're better at is draining your wallet.

Post# 915084 , Reply# 12   1/11/2017 at 09:14 (525 days old) by firedome (Binghamton NY & Lake Champlain VT)        
the current world vacuum tube market

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Right before he died Charlie K, publisher of VTV, did an exhaustive analysis of the state of the worldwide vacuum tube market, at that time about $50 million/yr in revenues, now close to $100 million. It was never published as the last issue, though it was in the can, (and I had done the editing, and had an article about Grommes/Precsion in it, and had even been paid for it), never made it to press, as he died the next month, however he had sent me a copy of his analysis. Vacuum tube production now is almost entirely Russia (Sovtek, ElectoHarmonix), China (Shuguang, Liuzhou) , some Eastern Europe (JJ), with tiny miniscule US production (Richardson) for a few esoteric military and broadcast types and hyper-expensive radio/audio types such as 300B types (Westrex under WE patents).

The guitar market in 2016 constitutes approx 90% of the total world market of new tube production by revenue, and the production and re-introduction of almost all current guitar/radio/audio types is virtually completely supported and financed by guitar mfr'rs such as Fender, Marshall, Guitar Center &c. New Sensor (Mike Matthews) bought the old Reflektor Saratov (USSR) plant in mid 2000s, a guy I know used to be the US Svetlana Chief tube engineer, and Matthews/Sovtek/EH now produces new tubes there under the Sovtek and Electro-Harmonix name as well many legacy names such as Genelex, Mullard, Tung Sol, Bugle Boy etc. and OEMs to Ruby and other big guitar suppliers. World 12AX7 production ALONE exceeds 700,000 units/ yr.

If it hadn't been for guitar demand, new production of all of these tubes would never had happened. While a few of the, mostly Asian, radio/audio crazies, and I have sold much to them, have forced a few tube types such 300b, 2A3, 45 and that ilk to new heights, the VAST majority of upward price escalation of desirable vintage tubes has been due to guitar gurus paying totally insane prices for once common and now in great demand tubes such black plate RCA 6L6GC, TS-6550, Tele 12AX7, Sylvania 6V6GT, Mullard metal base EL-34, Amperex Bugle Boy EL-84, &c to get that vital (in their mind) crunch or twang whatever, as guitars control even more of the vintage tube market than new. Go to and other vintage tube dealers to see just who they are marketing to.

So while the antique radio &c types like to talk about the "audiophool" effect, in reality its the guitar market that TOTALLY controls the market and prices. Now that CRT production has virtually disappeared, there would be no NEW tubes but for guitars, so we can all be thankful for that, while the audio, plus vital broadcast/radar/military, markets are less than 10%. However the other side of the coin is that it is also guitar players who have driven desirable vintage tube prices into the stratoshpere. Win some, lose some, good thing that I already have my lifetime supply, as I could never buy them now.

Post# 915109 , Reply# 13   1/11/2017 at 11:06 (525 days old) by Kb0nes (Burnsville, MN)        

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How about we step back a moment and look at the flip side. Imagine that there is no guitar market. All the reproduction and reissue new tube production would be less likely as the demand would be lower. All those desirable NOS tubes of old would command yet higher prices then they do today. And that would be just for the hifi demand since they could be the only available tubes.

Perhaps we should be thanking the musician world for lowering tube prices on the whole by making them available again? The guitar amp world is really where tubes make the most sense since they generally run them in the non-linear region which is where tubes really have an advantage. Run in a linear manner in a well designed circuit, tubes and solid state are generally indistinguishable from one another. I contend the 'warmth' associated with tubes is due to psychology from the look and feel (and smell?) of them coupled with the agreeable distortions of transformer speaker coupling.

Post# 915142 , Reply# 14   1/11/2017 at 14:21 (525 days old) by LordKenmore (The Laundry Room)        

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I think it's also worth noting with the home audio market that in some ways prices have actually dropped on tube amplifiers. At one time, there was no such thing as a cheap tube amp. They all cost $$$$, and I even recall seeing articles saying cheap tube amps weren't possible. (Output transformer costs were always a major issue.) But, thanks to China, we now have tube amps that are cheaper than, say, 30 years ago--and when one adjusts for inflation, the prices are really cheap vs. 30 years ago.


Of course, the question does come up how good those Chinese amps are... But they do appear to be a viable alternative to a budget solid state amp. The two complaints I've heard are poor sounding stock tubes (but that's easily fixed by buying better tubes), and possible power issues (which may or may not be a problem depending on the speakers, the room, and the expectations/hopes/dreams of the buyer).

Post# 915161 , Reply# 15   1/11/2017 at 16:32 (525 days old) by firedome (Binghamton NY & Lake Champlain VT)        
I did indeed note...

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in (paragraphs 3 & 4) that we have the guitar market to thank for production of most, if not all, tube re-issues and the continued production of new tubes. As I said there it's the flip side of the coin, current genuine vintage tube prices being the other.

Why care? The chief problem as that genuine premium NOS tubes, in general, are superior to new production for a variety of reasons: from scarcity or current unavailability of super-expensive reagent grade strategic metals for cathodes, high purity nickels, readily available at the height of the cold war, the quality of vacuum hardness due to adequate time not being taken to evacuate as much due to cost, to variability of grid spacing due to lack of ultra-precision equipment in the US and W Europe, most of which was scrapped at the end of the post-war tube area, now having to be re-created in China &c without that legacy knowledge base, and general lack of QC. East Bloc and China mfr'ers are now making tubes in batches of 10,000 at a time with emphasis being on numbers, not quality, as folks don't want to pay $100+ for a new 12AX7, but guitar guys WILL pay that for genuine original Telefunken Smooth Plates, I sold 60 of them last year to a guitar sales & repair outfit. The quality control, burn-in time, materials expected in 1960 is just not present today.

As to sound of SS vs tube, it's primarily due to the well known audio phenomenon, described in great detail in a back issue of IEEE magazine, of the way even-order 2nd and 4th order distortion harmonics prevalent in vacuum tubes are perceived by the ear & brain vs the prevalence of dry and harsher sounding odd order 1st and 3rd order distortion products which predominate in transistor produced waveforms, something easily observed by instrumentation as well. Also large amounts of feedback generally applied to SS circuits to reduce distortion and improve bias stability is detrimental, as are a number of other issues to do with types of caps that can be used in low vs high impedence designs, &c &c. Bottom line: we got rid of all our tube audio stuff in the 1970s for TOL SS stuff but quickly lived to regret it. We sure don't subscribe to all the silly line cord, wire, foam pyramids, stone feet &c other loonieness &c but we sure do hear the sweet sound of tubes. YYMV.

Post# 915685 , Reply# 16   1/14/2017 at 17:15 (522 days old) by sudsmaster (East of SF, West of Eden, California)        

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Every time I see a discussion about capacitors, I think about the 1950 Plymouth tube radio I restored about 20 years ago.


It wasn't working, you see. I set  up a six volt car battery on my dining room table, took apart the radio, and replaced all the tubes, the "vibrator" (a gizmo for turning six volt pos ground into higher voltage for the radio), and as a matter of course, I assumed ALL the capacitors had gone bad so I replaced ALL of them. Oh, and the speaker too, and I fixed the little pointer on the station indicator.


The end result was that the radio worked, but the volume was low. I could never figure out why.


Then after the Internet matured a bit more, I was able to figure out where I had gone wrong. I had correctly interpreted the values on the various cylindrical capacitors. But the little square ceramic ones sort of  threw me. Finally I decided, at the time, that they had the same color coding scheme as the more familiar carbon based ones. Turn out they have a different format, and I was likely off by at least a factor of 10. Which way? Which ones? Got me. I think I tossed all the old ones and didn't record their old positions. My best bet would be to locate another 50 Plymouth radio, open it up, and inspect for the square ceramic capacitor locations, record their color codes, and then figure out which ones on my car radio need to be fixed.


OK, that's my capacitor story. Your mileage may vary.


Post# 915831 , Reply# 17   1/15/2017 at 19:14 (521 days old) by cfz2882 (Belle Fourche,SD)        
'50 plymouth radio

might be a schematic such as Sams that will give the proper values for the caps to get that Plymouth radio working proper again :)I haven't had too many capacitor incidents worth reporting-on my '62 Stromberg Carlson school PA tuner,and '81 RCA garage TV,bad filter caps were immediately obvious :) the 2004 home PC and the 2010 vmw cabrio washer took a little figuring to conclude those needed recapped! junk Chinese capacitors that expired waay early were the cause of both those devices becoming inop.Have had a couple selenium stinkfest incidents though:1 st was when I took apart a small 1960s SS phono,then decided to use the amp-hooking the poer wires direct to cord instead of off low volt aux winding on motor :)About 12 at the time,noticed a tiny epoxy encapsulated rectifier had blown up,but didn't know what selenium rectifier was.2nd was when I included a selenium bridge rectifier into a project powered by 115 v and didn't know they only handle ~30v per plate-powered up the device and the rectifier held for about 1.5 seconds before it let go under the chassis spewing gawd-awful rotten egg smelling red smoke and fouled the underchassis area with reddish smoke deposits :)
Back to capacitors,poking around some Studor-Revox forums,discovered the "Frako" capacitors found in a lot of German and some other European equipment is supposed to be extremely suspect and I have Frakos all over the place in my german and Tandberg home audio,old Blaupunkt car stereo gear,VDO gauges,even my Porsche 928 :) Hardly any trouble with any of this except some very small Frakos where the rubber bung had shrank and cracked with age and caps went bad-could not find correct replacements,so had to remote mount a larger size cap and string wires so my Blaupunkt cassette would work again :)

Post# 915837 , Reply# 18   1/15/2017 at 19:31 (521 days old) by panthera (Rocky Mountains)        
graceful clipping versus hard

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We've all covered this territory many times. In the end, it's easier to get first class, low distortion out of tubes than transistors. That doesn't mean one can not, but it takes really good logic control to do it.


Post# 915864 , Reply# 19   1/15/2017 at 23:47 (521 days old) by kb0nes (Burnsville, MN)        

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It is FAR easier to get low distortion out of solid state designs then any tube design, especially when we look at a power amplifier and consider the system. Voltage amplifiers are a bit of a different animal... When one considers the need for an output transformer to couple to the speaker, then the distortion is always going to be high. Typically when I measure a tube amp near full output at 1Khz I get distortion of .5 to 1%, every solid state amp I own will be .01% or better (possibly excepting some early Dynaco Stereo 120's that were pretty vile). Move to the higher and lower frequencies and the tube stuff looks really bad.

Now I do agree that if you push a tube amp into a non-linear condition it is bound to sound FAR more musical then a solid state amp pushed to clipping. But the rub comes that it is difficult to develop real power from a tube amp, anything over 50-60 watts takes some doing. So therefor you will clip that tube amp a lot more often. A 250 watt per channel MOS-FET amplifier has scads more headroom then any tube amp I have ever owned.

I love tube gear for the nostalgia, and the simplicity of the circuits that makes them easy to build and repair. They are especially well suited for musical instrument amps that are intentionally clipped. But a good modern solid state amplifier is far more accurate to it's source. If tube's were so all fired accurate then all the lab instrumentation amplifiers would be tube designs (they aren't). But tube amps can offer a lot of "agreeable" distortions that can make them very endearing, which is why they have the resurgence they do today.

Post# 916220 , Reply# 20   1/18/2017 at 12:46 (518 days old) by firedome (Binghamton NY & Lake Champlain VT)        
It isn't...

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about the degree of distortion or the "accuracy" as much as it is about the type of distortion, as clearly described in the IEEE article referenced above. A distortion of .01% is essentially meaningless when the amplified signal is ultimately perceived through analog mechanical transducers such as speakers that are lucky to have a distortion of under 5%.

Post# 916292 , Reply# 21   1/18/2017 at 21:23 (518 days old) by Artcurus (Odessa)        

LOL, When I rewired a building that had knob and tube (ACTIVE!) wiring, I probably could have made a fortune selling that wire (and the ceramic connectors and the 1920's dust of course) to audiofools. ;-)

Post# 916293 , Reply# 22   1/18/2017 at 21:27 (518 days old) by washman (Butler, PA)        
I was told once

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the only thing that matters is Gibson and Marshall. He said if you don't play Gibson and Marshall, you're a wanker!

His name was Ian St. Ian.

Post# 916676 , Reply# 23   1/21/2017 at 01:40 (515 days old) by tolivac (greenville nc)        

An aquantence that works with me at the transmitter plant has a friend that can "hear" the differences in battery brands in his guitar effects stompboxes.I figure that musician has a very VIVID imgination or does he have dogears?

Post# 916755 , Reply# 24   1/21/2017 at 12:04 (515 days old) by panthera (Rocky Mountains)        

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I agree that, today, in 2017, it is quite easy to get great sound out of solid state amps.

I was mainly thinking about vintage days. 

Indeed, the major advance in solid-state sound is due to logic control - look at the Class 'D' (and, as you know, but most do not, 'D' does NOT stand for digital) amps. There are now some really good ones.

I'd still wager that a really well designed class 'A' triode circuit, using logic control would equal the best solid-state design, using logic control in sound. If you're looking for high output, there's no alternative to solid-state. If you're looking for really high-efficiency, there's no alternative (realistically) to Class-D solid-state. 


As a victim of perfect pitch, monotonically decaying harmonics appeal to me enormously. 


But, again - it's 2017. I'll stick with my SET power amps when I have the choice.


As to the rest of the low-oxygen, single-crystal copper nonsense, etc. - pass.

Post# 916869 , Reply# 25   1/22/2017 at 00:58 (514 days old) by tolivac (greenville nc)        

Class "D" amp-not new-been with us since the early 70's Class D modulators in AM transmitters and high power SW transmitters.Will be turning ours on in about 8Min-500Kw.250Kw Class D single tube modulator.When tubes or SS used in a Class D ampEFFICIENY is the thing here-more power out with less power drawn.And the switch stage runs cooler-the device is acting as a switch.In our case a single TH580 tube.30 KV supply voltage.The tube also acts as a switching voltage regulator for another TH580 tube as the RF power amp.Car stereos today have Class D amps in abundance.My car has them.600W.Some receivers on the market now are equipped with them-and they work and good!If you want a single end modulator--our Continental electronics 420A 500Kw SW transmitters have this-The modulator feeds audio to the grids of the power stages.Modulator is 4 845 tubes in parallel cathode follower-driven by one 845 tube and two 807.Bet the audiophools would love that!

Post# 917013 , Reply# 26   1/22/2017 at 20:06 (514 days old) by panthera (Rocky Mountains)        
once the 12ax7 op-amp was produced in quantity

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All sorts of groovy things became possible. I wish our transducers were up to the reproduction accuracy of our amps....

Post# 917045 , Reply# 27   1/23/2017 at 00:19 (513 days old) by tolivac (greenville nc)        

You build a speaker-"transducer" that is up to par with modern amplifiers-the world would definetly beat a path to your door.And efficiency of them too!They are still inefficient-hence all of the high power amps hawked out there.Close ones in efficiency and accuracy--Altec Lansing Voice of The Theater and Klipsch K-corner horns.These two can perform well and with lower amounts of amp power.

Post# 917093 , Reply# 28   1/23/2017 at 10:14 (513 days old) by panthera (Rocky Mountains)        

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My sole contribution to the field of transducers was my Master's Thesis - a program which identified whether a stylus was within a set of given parameters or out of range (damaged/dirty) with a calibration sequence to compensate for the (at that time) wild diffusion variations of (what we then called) hi-output LEDs.


Ah, those were the days.


I don't really get upset about 'distortion', it's a word similar to 'allergy' and about as useful without more information. Some forms of distortion really, really bother people cursed with perfect pitch (there was a study in Germany at my university about that in the 1980s. An early attempt to figure out why so many young people (good hearing) and older adults (down below 8kHz) could tell the difference between CDs and master tapes. Several interesting anecdotal results and a few repeatable observations, one being that those of us with this congenital deformity are super-duper 'allergic' to third-order harmonic distortion.


In the end, of course, nearly all the problems with early CD sampling turned out to be that the solid state mic. amps were driven to clipping. This is why so many recordings on 35mm tape from the '50s through the late '60s sounded so good on CD and the junk from the '70s and early '80s sounded so bad. Once sound engineers started making recordings using late-20th century technology properly, instead of acting like it was still 1957, the recordings began to sound as good as that limited sampling rate permits.


Too long a post, too much coffee this morning. Efficiency isn't our problem, today. Getting the transducers closer to being 'transparent' is. No clue how to solve that, gosh, we can't even figure out whether it was mold or varnish which made the Stradivarius and Guarnairi instruments sound so good - and today's precision made Baldwins sound like trash.



Post# 917253 , Reply# 29   1/24/2017 at 02:54 (512 days old) by tolivac (greenville nc)        

Some "young" people really don't have such good hearing-the old mans may be better-Remember those young-ems blast their ears with their cranked up car sound systems and headphones.When I talk about efficiency of speakers-they are still less than 50% efficient-most of the amplifier power is wasted as heat!Can go with you on the mic preamps.One time down here at the transmitter plant heard stranger modulator "talking" in our AEG transmitter-the one with the Class D modulator.Turned out a console module was strapped for mic preamp gain and being fed with a line lever signal-clipping for sure.And not good for transmitters!In early days of recording engineers not only didn't drive their mic levels to clipping-they knew what TYPE of mic to use for a particular instrument or singer.And the tubed custom consoles then helped out a lot-when the 60-70's came about the boards had really CRAPPY-and I mean CRAPPY mic preamps-when they were driven too hard-the HORRIBLE recordings were the result.Fortunately the custom tube RCA (3 channel) consoles were restored and used in the remakes of the SACD RCA "Living Stereo" Have these-and they do sound so good,clean and like you are there!Didn't know Baldwin made violins?Know they make pianos.I don't have perfect pitch-can't play a musical instrument-only ones I can "play"are those automatic ones played from a roll or perforated cardboard music "book".Would love to have a band organ collection-but don't have the space or money!Instead have "collections" of them on CD or MP on my phone.Also 50-60 records sounded so good,too-becuase the folks then CARFED about quality and knew how to do it!Instead when later 60-70 and onward-music was so badly and heavily PROCESSED to sound good on radio airplay than for listening.

Post# 917294 , Reply# 30   1/24/2017 at 08:41 (512 days old) by panthera (Rocky Mountains)        
Be glad you don't, Rex

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It's a curse. Remember that fight discussion here a few years back on whether a particular blonde 'singer' was auto-tuned? Those of us cursed all knew she the singer was and her the aficionados were merciless in blasting us for daring to think such untrue thoughts.

Turned out, of course, they were wrong, as she freely admitted in an interview not much later. It's not a 'gift' unless you're a fretless string instrument player or play one of those wind instruments which require enormous skill.


Yeah, the 'hard' clipping problem were a major source of bad quality recordings, as was the 'who cares', it's just trash for the kids, they can't tell the difference mentality of much of that disposable era. Today, of course, you have many musicians (Chris Rupp, Cher, Kiri Te Kanawa, to name but a few) who know more than enough and who actually care enough to work with the studio engineers to produce the best quality sound possible. Back then, well - the problems are well enough known for me to have read about it, and my interest is purely that of a rank amateur. 

This post was last edited 01/24/2017 at 09:57
Post# 917323 , Reply# 31   1/24/2017 at 10:56 (512 days old) by firedome (Binghamton NY & Lake Champlain VT)        
Auto tune...

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is the work of the devil.

As to Kiri, sadly she's so past her prime production hardly matters.

Post# 917339 , Reply# 32   1/24/2017 at 11:28 (512 days old) by panthera (Rocky Mountains)        
It depends on how auto-tune is applied, actually.

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Just a breath of the newest incarnation of the software can make a gigantic difference, to the good.

Most studios and nearly all performers, however, haven't a clue just how obvious it is.

As to Kiri, well, gosh - I've recently heard much younger singers perform far worse in some of the best houses in Germany.

Yes, each singer needs to focus on different material at each stage in their career. I've heard really good tenors who, in ten or fifteen years might well have been outstanding Heldentenore ruined by too much Wagner in their early 20's. I've heard a 74 year old pull off Zoser(Aida) with bass notes that shook my chair and a D# which was clear as a bell. Of course, that was in the National Theater, Munich. had a subscription in the Parkette Mitte for years and years. Have to say, they did Parsifal 10^14 better than Bayreuth and Der Ring about as awful, regardless of singers, as any I've ever heard, anywhere.

Post# 917464 , Reply# 33   1/25/2017 at 03:23 (511 days old) by tolivac (greenville nc)        

For us at the transmitter-SW,"auto-Tune" is for when the transmitter can tune itself when brought up.So far the EAG is the only auto-tune one we have that works.Took a man from its factory in Germany to correct its problems.On occasion you have to help it.The other transmitters here you have to tune them.For me tuning them is not a real problem.Have to show the other guys.Now they can do it with no problems.For musicians not familiar with their "auto-tunes"

Post# 917511 , Reply# 34   1/25/2017 at 12:23 (511 days old) by panthera (Rocky Mountains)        
Auto-Tune, Tubes

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I always have to laugh when some idiot insists that 'tube' technology isn't as good as 'solid-state' on one of the Yahoo forums.

Usually one of us who actually have a brain cell or two fire back: Do you listen to radio broadcasts? Own a microwave oven? Drive a car with a bright display that you can read clearly in the glaring sun?

You do?

Oh, OK - guess you're right, then. Not.


I hadn't thought of your sense of auto-tune. I suppose the amount of drift permitted is pretty regulated? No idea about it, really.

Post# 917535 , Reply# 35   1/25/2017 at 15:35 (511 days old) by kb0nes (Burnsville, MN)        

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In general it isn't a matter of tube technology not being "as good", there is no doubt that vacuum tube technology does excel is several areas, mostly durability. But alas that comes at a price, in most all applications tube technology is expensive. This is the reason that tubes have been replaced in almost all applications up through UHF at least.

Assuming that a TV or radio transmitter is still tube is likely to be an incorrect assumption. If it was built in the past 20 years, and it isn't a high UHF channel or excessively high power transmitter, it is likely to be solid state. Our local Channel 2 analog transmitter was solid state in the early 90's. Most all the TV & FM transmitters at our local tower farm are solid state today.

The advent of LDMOS solid state technology was what did in tubes for RF uses. They are even selling transistors capable of hundreds of watts at 2.45Ghz now so in the not too distant future domestic microwave ovens will probably be solid state too, although China made magnetrons are damn inexpensive.

A very common vacuum tube used for amateur radio is the Eimac 8877/4CX1500. Using one of these tubes you feed it 4000 volt at .75 amps and it will give you 1,500 watts of RF up through about 300Mhz with only about 10-15 watts drive (~15db of gain). The new LDMOS transistor boasts almost identical performance numbers, but has the advantage of running on a 50 volt supply. And 8877 is a $1000 tube today, the LDMOS transistor is ~$200 and it doesn't need the high voltage supply and high impedance high power matching network. Tubes are dying quickly for RF use. If you need many Kw of power you just combine a bunch of amplifier "pallets" to get the output you want. In this way they are more reliable then tubes as a failure of one amp hardly reduces output power. A failure of the tube final and you are at exciter power :(

Here is a neat video of the Freescale Xtremely Rugged series of LDMOS device showing it's durability. I used to be a devout tube guy (anything over 100 watts needs a filament) but no more!

Post# 917559 , Reply# 36   1/25/2017 at 18:35 (511 days old) by panthera (Rocky Mountains)        
Technology marches on!

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I think that's totally cool, thanks for the info, Phil. I didn't realize solid-state had made such advances 20 years back.

Given my professional background in IT, I am obviously happy with whatever works well and is reliable.


Post# 917583 , Reply# 37   1/25/2017 at 21:19 (511 days old) by norgeway (mocksville n c )        
If you want to hear

How much better tube stuff sounds in general...Listen to a Hammond Organ played thru a 147 Tube Leslie and one played thru a newer solid state leslie..its night and day, likewise listen to my 62 Zenith stereo and then listen to one a few years later....

Post# 917919 , Reply# 38   1/28/2017 at 03:15 (508 days old) by tolivac (greenville nc)        

I really like that BLF-570!!!!Wish we could use those in the RF drivers out our way.SW transmitters running at 100kw,250kw and 500kw still use tubed output stages.Mainly for simplicity.The modulators are solid state-PSM---(Pulse Step Modulator) it is a form of tubed PDM but without the tube.It is replaced with the PSM modulator modules arranged in series with each other they then do two things-provide the B+ DC plate voltage for the tube stage and the modulation.The first generation PSM in the BBC transmitter is VERY trouble prone-the later CEMCO version is less troublesome and more reliable.The PSM modules are easier to replace-on one big fibergalss board and use Bipolar power transistors instead of the GTO-and they are air cooled-not water cooled as the BBC modulator is.
4CX-1000,1500 tubes often were used as drivers in very high power FM and TV transmitters.TV transmitters still had some tubes in them 20 yrs ago.Typically the visual PA and Aural PA.Worked on this so I know.The drivers were solid state-and actually in those early generation (RCA) LESS reliable than the tubes they tried to replace.But with the advent of that MOSFET style power transistor-things have changed.For HDTV transmitters-those in the UHF range still use klystron and klystrode tubes.VHF digital TV transmitters are now solid state.With DTV LESS power is required as opposed to analog.LW and MW AM transmitters are solid state today-even at 500KKw,1MegW each power module is 500W They are combined to derive the final output.VOA has some of these transmitters-made by Harris -the DTX 500 and 1000 series.Haven't used these personally-those that have like them.They do take up more space than an equivalent tube transmitter.Sodlid state has made inroads--but don't count tubes out yet-they are making technical inroads ,too-better efficiency.

Post# 917980 , Reply# 39   1/28/2017 at 12:37 (508 days old) by panthera (Rocky Mountains)        
This is great stuff,

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Rex, Thanks!

Post# 918042 , Reply# 40   1/29/2017 at 00:32 (507 days old) by tolivac (greenville nc)        

Sound quality-When a friend of mine and me were servicing the AM stations we noticed how much better a high level plate modulated AM transmitter sounded on the air over solid state and PDM ones.The high level I am talking about are rigs that have push pull tubed modulators.Often the same tube as the RF PA.Again in the high level broadcast aM-and many SW transmitters the modulator is noting more than a very powerful PP audio amplifier.The modulator tubes have a bias adjust exactly like on a hi-fi amp or a guitar amp.When the tubes are good and bias adjusted right-the sound quality was almost magic.The Harris DTX transmittrers do sound much better than earlier SS transmitters.Remember Harris MW-1 AM broadcast(1Kw AM) the PA comprised of 6 power modules with standard TO-3 transistors.When they shorted-common---the circuit board traces must have glowed like toaster elements and blew before the board fuse did.Had to repair these with lots of wire jumpers.Liked the tubed 1Kw AM's better,4-400 tubes as RF amps and modulator or big glass 833 triode tubes as PA stage or modulators.One time we serviced a rig-Harris 1G the blower failed-Tx was still happyly playing away on air--tube plates really glowing-when we entered the building smelled REALLY "Hot Glass"The tube envelopes were sucked against the plates and they were still going.Fixed the blower and put in new tubes-all was right with the world again.Shows how tough those old 833's are!!Was a place in Baltimore.

Post# 918043 , Reply# 41   1/29/2017 at 00:40 (507 days old) by tolivac (greenville nc)        

'Nother thought for tubes-one other fellow that works with me at the transmitter can tell this-not sound quality,reliability,efficiency---but the SMELL of tubed stuff.The hot glass,dust on the glass.Now if the tube device is in a wood cabinet-like a radio,TV,or Hi-Fi console-the smell of the wood added to the hot tubes!Anyone else out there noticed? Take a good wiff next time you play your tubed device!

Post# 918044 , Reply# 42   1/29/2017 at 00:45 (507 days old) by LordKenmore (The Laundry Room)        

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Yes, I've noticed the tube smell on old radios. It was something my mother noted, as well. (She had grown up with tube technology in both radios and TVs.)

Post# 918046 , Reply# 43   1/29/2017 at 01:08 (507 days old) by ea56 (Sonoma Co.,CA)        

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I remember the old tube radios and TV's very well. The sound was so much richer and natural, there was warmth if you will. I used to own a 55 Cadillac Coupe deVille in 1974 and it had a tube radio like all cars of this vintage did. After I would start the car it would take about 30 secs of so before the sound would come out of the speakers as the tubes warmed up, and it would almost swell, the volume gradually getting louder until it reached the set level. I think the song "Coming to You From Out of Nowhere" may have been based on the way the sound came out of the early radios.

My family had an RCA HiFi that my dad purchased in 1956. It had a beautiful cherry wood cabinet and the most beautiful sound I've ever heard out of any radio. I think that the vacuum tubes and the heavy wood cabinet combined with the huge speakers are what gave it such a rich sound.

This post was last edited 01/29/2017 at 02:48
Post# 918083 , Reply# 44   1/29/2017 at 09:47 (507 days old) by panthera (Rocky Mountains)        
Because HI-FI

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was so gosh-darned expensive in the 1950's, manufacturers had no choice but to compete on quality. People invested the time to actually listen and look and work the devices. Today, I order a 12AX7 or a 12AX7A (low noise) and cross my fingers it won't be too awful at a price which is absurd.


Magnavox, back when it wasn't Philips cheap, bargain brand, put real engineering and applied acoustics into their consoles. The astro-sonic solid state amps had lousy high-frequency performance (among other flaws), so the unusual horns. The Micromatic turntables had rumble problems, so the channel separation at 100 Hz was very dampened.


I think the matter comes down to human hearing more than anything else. All people (even old folks) are really sensitive to transients. Tube amps of that era did enormously better than solid-state amps (hell, to this day rise time is one big measure of an amp's competence). Second, odd-order distortion is anathema to those of us cursed with perfect pitch, yes. But normal people without that hearing defect are also really attuned to it and don't like it. When poorly designed solid-state amps are pushed too hard, ouch - immediate third-order harmonics and other nasty clipping artifacts which hurt. Tubes fail gracefully when pushed up against their ceiling. The artifacts in the odd-order are much lower.


Finally, we can argue the lab. measurements. Take a well-designed, logic-controlled Class A tube amp and put it up against a well-designed, logic controlled Class A solid-state amp and what comes out of both is going to look great on paper. Very few of us can afford that level of quality.


I like classical music. It's a tough challenge to meet with anything but really high-quality solid-state. It's not so hard to do it with a good tube amp. Again, it's the transients (where measurements and perception line up) and the make up of the harmonic distortion (where they don't line up 1:1) which matters to our ears, not the 'facts' on paper. 


Good discussion of the whole matter at the link.


Post# 918097 , Reply# 45   1/29/2017 at 11:30 (507 days old) by kenwashesmonday (Haledon, NJ)        

I believe the "A" suffix on a 12AX7 tube means controlled warm-up time so it can be used in series filament circuits. The low noise version of a 12AX7 is a 7025.

Post# 918108 , Reply# 46   1/29/2017 at 14:08 (507 days old) by firedome (Binghamton NY & Lake Champlain VT)        
The IEEE Spectrum article...

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"The Cool Sound of Tubes", referred to by me much earlier in this thread, and again just above, you will note was written by my friend Eric Barbour, the former Tech Editor of the magazine that I edited & wrote for back in the day: Vacuum Tube Valley. Eric was also Vacuum Tube Engineer for Svetlana, which is now part of the Russian tube manufacturing companies owned by Mike Matthews of Groove Tubes &c. IMO Eric probably knows more overall about vacuum tubes than possibly anyone in the world. His many tech articles about the history and development of numerous audio tube types are unmatched anywhere.

Post# 918109 , Reply# 47   1/29/2017 at 14:14 (507 days old) by firedome (Binghamton NY & Lake Champlain VT)        
memory glitch...

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actually Eric was Senior Editor, mostly John Attwood was Tech Editor, followed by Lynn Olsen towards the end of the run... RIP our Founder/Publisher and my greatly missed good friend, Charlie Kittleson.

Post# 918130 , Reply# 48   1/29/2017 at 17:28 (507 days old) by panthera (Rocky Mountains)        

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The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics.


Post# 918136 , Reply# 49   1/29/2017 at 18:13 (507 days old) by kb0nes (Burnsville, MN)        

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Ken is correct, the 7025 is a specially selected 12AX7A tube that was deemed to be lower noise and likely had more robust mechanical construction. I have had better luck with 7025's in the first preamp position in my Marshall guitar amp, I have never had a microphonic one.

The 12AX7A was an improvement that brought a different filament winding to try reduce hum induced from filament current.

Post# 918151 , Reply# 50   1/29/2017 at 19:36 (507 days old) by panthera (Rocky Mountains)        
I didn't say

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the 7025 wasn't a low-noise variation, but so is the 12AX7A. Says so right there in the data sheet.

There's an enormous number of variations on this tube, some I didn't even know existed until this thread.


As to the GE 12AX7A, it's about $80 a pop for NOS and the Shuguang about $10 for the 7025/12AX7 so there's not much to discuss. I just happened to recollect the GE 12AX7A as being a low-noise upgrade I made in the 1980's for an ancient moving-coil pre-amp I'd put together in 1969.  If I were doing a guitar amp, the Shuguang would be the better choice for microphonics, clearly.

Post# 918200 , Reply# 51   1/30/2017 at 00:58 (506 days old) by tolivac (greenville nc)        

Type 5751 is a military-low noise version of the 12AX7.-Also this tube has lower microphonics-the elements are better reinforced.
Yes,the Astro-Sonic like other early solid state amps were TERRIBLE.The older TUBED Magnavox was best.I had no problems with the Magnavox Imperial and Micromatic TT's were good tables.The change mechanism was powered separetly off the motor.Also with some SS amps-you drive them into hard clipping---there goes your tweeters!Tweeters HATE clipped waveforms-blows them instantly!So that is the case of a low power amp being more dangerous than a higher powered one.Seen that several times.Even had to repair a tweeter horn from that.
At the transmitter we use Shuguang 845 tubes in the CEMCO modulators!Work great.

Post# 918238 , Reply# 52   1/30/2017 at 09:16 (506 days old) by panthera (Rocky Mountains)        
12AX7 Family

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This tube has been around so long, been so versatile and does it's job so well. This thread prompted me to do research on it. Impressive little high-voltage beasty.


The first electronic op-amps were realized with 12AX7 tube - pretty much only used for the war effort, of course. Wow. That was over 70 years ago!

Post# 918280 , Reply# 53   1/30/2017 at 14:21 (506 days old) by firedome (Binghamton NY & Lake Champlain VT)        
the highly regarded 12ax712ax7a/ECC83 &c...

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are the most popular audio tubes in the world, over 200 types being produced in 40 factories since introduction in March 1948 by RCA (see RCA tube manual RC-15), then shortly after by GE and Sylvania, later Tung-Sol, Nat. Union, CBS-Hytron, Raytheon, &c, followed by European ECC-83. They are essentially 2 x 6av6 triodes, mu = 100, in one tube. 12AU7/ECC82 and 12AT7/ECC81 are medium and low mu but very similar dual-triode tubes, the obsure 12AD7, 12BZ7, 12DF7, 6679, 6681, 6851 &c are also similar types.

High gain, low noise, and low hum, the 12ax7 types gained huge popularity mainly due to preamp use with the original GE Variable Reluctance low output magnetic phono cartridge. The original 12ax7 was found somewhat wanting so the military/industrial 5751 was introduced in 1950, a ruggedized mini 6SL7, and then a more cost effective 12ax7a for consumer (hi-fi) use. The superior Phillips/Miniwatt ECC83 with the precision grid winding of the 5751 and better cathode materials debuted around '52, followed by Telefunken, Mullard, Brimar, Valvo, MOV, Tungsram and other Euro versions. Most higher end US hi-fi mfrs such as Fisher, Scott, McIntosh &c used the Euro produced tubes re-branded with their own logos as they were truly superior (quieter) to the US tubes. The US competitor for the ECC-83 was the 7025, a std 12ax7a with coiled heater to reduce hum, more expensive, most were sold to guitar amp mnfrs.

All currently produced 12ax7 variants are Russian, East Europe or Chinese origin. Among the most desirable vintage variants are generally conceded to be the Telefunken smooth and ribbed plate ECC83 versions along with Amperex (Phillips) Bugle Boy, and the super rare Telefunken ECC803s gold pin, the latter bring over $1000 each on occasion!

Post# 918457 , Reply# 54   1/31/2017 at 14:17 (505 days old) by kenwashesmonday (Haledon, NJ)        

panthera wrote:
"The 12AX7A is a low-noise double-triode. Please reference the data sheet link. GE marketed them specifically for their low-hum and microphonics."

Can't argue with GE's data sheet. Thanks for the info!

Post# 918499 , Reply# 55   1/31/2017 at 19:02 (505 days old) by panthera (Rocky Mountains)        

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Doesn't change the fact you may be right, too - goodness, there's supposedly a 12AX7HD from 2015 which is considerably better on noise/hum/THD. For a humble triode pushing 80 in it's original design, this sure has been a winner.

Post# 918539 , Reply# 56   2/1/2017 at 01:45 (504 days old) by tolivac (greenville nc)        

The 12AX7--was a workhorse then-still is now!!May they live on!!The uses for that tube are just plain endless!The data sheet is just like what is in my GE tube manual.Have several RCA tube manuals and a Sylvania one around somewhere.Also the RCA master manuals that list transmitter tubes and large rectifier tubes.Mercury vapor ones,no less.The Audio nuts are discovering those!Liked them in older broadcast transmitters!

Post# 918554 , Reply# 57   2/1/2017 at 05:48 (504 days old) by kenwashesmonday (Haledon, NJ)        

The manual I use on my workbench is GE's "Essential Characteristics" from 1973. It goes all the was back to the 01A tube. A slightly older version of that book, and many other tube manuals, is available at the link below.

CLICK HERE TO GO TO kenwashesmonday's LINK

Post# 918556 , Reply# 58   2/1/2017 at 06:07 (504 days old) by tolivac (greenville nc)        

The GE book I have is the Essential Characteristic-but don't what date it is.In one of my MANY boxes and milkcrates of books!

Post# 918593 , Reply# 59   2/1/2017 at 10:15 (504 days old) by firedome (Binghamton NY & Lake Champlain VT)        
It's good to have a number of tube manuals...

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from different eras, as older types, 4,5 pin and the like tended to be dropped from coverage as newer tubes such Novar and Compactron types were introduced, and tube manufacturers sometimes didn't list tube types they didn't sell. Many many types were re-branded and sold by mfr's who didn't make them, a common practice even still.
We have 7 or 8 manuals from the '30s to '70s, GE, RCA, Sylvania, Tung Sol, which pretty much covers the field.

Same with tube testers: early ones wouldn't have sockets and test data for later tubes, and usually vice versa, as later testers eliminated many obsolete tube types. The Hickok 539c is one of the more versatile, along with certain military TV (TV-2, TV-7, TV-10 &c) types. Probably some of the best ever made were the British AVOs, possibly some rare German and Russian ones, none of which we've had... we sold all our testers a few years ago when the stock of tubes went from many thousands to a few hundred, keeping only those types to support current equipment.

For those really interested in tube history Ludwell Sibley's book is one of the best.
Below, some of our inventorty, all audio/radio types:
I have a few spares/oddballs if anyone needs anything.

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