"Audio" Valves

[PJL]

The ECC82 and ECC83 low frequency double triodes were for general use and appear in military, industrial and test equipment, and of course audio. They were just the latest in a progression of LF triodes that started in the 1920's.

[ionburn]

Originally Posted by G4XWDJim

I have a new tray of wire ended ex mil ECC8*, they may even have a CV number. I can’t remember which version as I haven’t seen them for 20 odd years. At the time of finding them I heard that they were intended for the electronics in missiles or some such application.

Anybody know anything about them.

I am aware of some types of EF*, EF73 for example but they are pentodes. I would be interested in knowing the numbers if anyone knows. There have been miniature types like the CV2269 electrometer triode.

I should also add that I have some Russian miniature double triodes. These are often copies of US design so there may well be a miniature US 12AX7 equivalent.

[Dave1000]

Some Russian designs have the heaters connected differently so they are not drop-in replacements for western valves that are otherwise identical - something like 6N2P are ECC83s, but not the same heating arrangement.

Bare leadwire/flying lead ECC8*s (rather than pins) are not uncommon, although I have never read of any claim that they were for missiles, just meant for hard-wiring into boards, although that could easily be missiles, I suppose.... They usually sell for surprisingly little, presumably because people just cannot be bothered to solder or otherwise fit them into an octal plug or suchlike. They obviously carry their own CV number - an ECC83 with flying leads is a CV4035. There are examples online in the Valve Museum.

[snowman_al]

Originally Posted by G4XWDJim

Anybody know anything about them.

CV4033 wire ended equivalent to ECC81 12AT7 CV4024
CV4034 wire ended equivalent to ECC82 12AU7 CV4003
CV4035 wire ended equivalent to ECC83 12AX7 CV4004

[Radio Wrangler]

Originally Posted by Dave1000

I was curious about what valves were used for in their heydays.

They were used for just about everything.

Plenty were used in test equipment from audio wien bridge oscillators to RF signal generators. Comm and nav radios in aircraft... auto pilots, radio altimeters, Radar IFs and pulse generating oscillators, display sweep generators. EHT generators. Regulated power supplies, Navigational beacons, IFF systems, gun directors, intercoms, transmitters, exciters, modulators. Phone FDM channel combiners, scramblers, teleprinter modems, encryption and decryption machines. computers both analogue and digital. Direction finders. Entertainment radios, cinema amplifiers, tape recorders.

Valves were, in their day, a lot less application specific than modern semiconductors.

David

[Refugee]

The best test I can think of is to locate a vintage amplifier where the double triode is implemented as a cathodine phase splitter (one section is a voltage amplifier and the other has the grids of the output valves connected to the anode and cathode).
This is easiest if the amplifier uses an octal double triode.
Make up some adapters and try out different double triodes.
There are just three test points for the scope probe on the grids of the output pair and the anode of the voltage amplifier.
Just look for even clipping as you drive it up to full power.

[Dave1000]

My question was really about valves use and what that means in terms of current sources for valves long since manufactured.

Quite why any valve does or does not sound different to me or anyone else is interesting to me, but will be forever be a subject of wider debate, I very strongly suspect. I am very much more than willing to accept that what many people, including me, find aurally attractive about valve amplification is the result of all manner of distortion, harmonics etc., that never ought to be there. All I know is that it is all harmless fun that costs not too much - just another boys' toy.

[ionburn]

Originally Posted by snowman_al

CV4033 wire ended equivalent to ECC81 12AT7 CV4024
CV4034 wire ended equivalent to ECC82 12AU7 CV4003
CV4035 wire ended equivalent to ECC83 12AX7 CV4004

Thanks for this. I see they appear to be the same as the pinned variety but with wire leads, rather than miniature equivalents, so maybe not for missiles. I checked on the usual sale site - being wire ended does not seem to have reduced the premium lol

But it's all a matter of belief systems.

You can have belief (a thought hold without any evidence) or a system (where at least something has to be verified to carry on), not both. A bit like "service industry" it's either one or 'tother.

[GrimJosef]

In the end it's about the definition of words, but I don't think that there necessarily has to be anything attached to the external world, and verifiable there, in a system. The only thing which a system really has to be is consistent. There's nothing externally verifiable in either the metric system or the imperial system. They're purely abstract human constructs. A system of beliefs surely qualifies on the same grounds doesn't it ?

It could still be wrong of course. Newtonian mechanics is a system based on the constancy of mass and the possibility of limitless speed and an absolute value of time in all reference frames. It works well enough in almost all circumstances down here on earth. In reality though none of those premises is actually valid. But that doesn't mean it's not a system.

Cheers,

GJ

[G6Tanuki]

Originally Posted by robinshack

I have a quantity of "NOS" JAN 12AT7WC of USA manufacture in the 1980s. Packed in sleeves of 5. Barcoded labels affixed and marked NAMSA. (NATO supply agency).When I tested some, they have a far wider spread in characteristics than consumer brand 12AT7.

The wider 'spread' of electronic characteristics as you measured might have been perfectly acceptable in a military missile application where ability-to-survive-a-one-off-100G-acceleration was what was primarily specified in the requirement.

I'm reminded of a relative who spent ages designing and optimising a particular op-amp circuit, with loads of stabilising feedback-loops, long-term-stable components and such. It was rejected at review and he was deeply offended. The circuit-in-question was part of a guided-missile and its design-life could be defined as "You have 90 seconds to realise your life-ambition and explode; if you fail please-please-please don't try to come home!".

[Dave1000]

Not wishing to muddy the waters, but I am curious about valves commonly used in audio power amplifiers. This is pure curiosity on my part as I do not own one and have no plans ever to do so.

I appreciate that over the years many and various valves will have been employed, but does the same general comment apply to things like EL34s, just as a for instance, as for ECC8* valves - "designed" for audio amplification but found many and various uses outside of that use?

[GrimJosef]

EL34s were really designed as audio power output valves. Their high gm, for example, set them apart. But earlier power valves included some with a wider range of uses. 807s were used at RF but also at audio frequencies and worked perfectly well as series pass valves in regulated power supplies. The 6L6, which was used in plenty of audio amps, was famously also deployed in the servo control for gun turret positioning on one of the US heavy bombers. Going in the other direction PL509s and 519s were designed specifically for use as TV line output valves but their high peak current capability means they've also been used in output-transformerless audio amps.

Cheers,

GJ

[joebog1]

As a confirmed Hi-Fi nutter, I have also chosen to find the "ultimate" sound.
About the only valve (I have found) that is specifically designed for low level audio are the miniature versions like the pic shown.

I was told they were designed for early fighter jets. For R/T and intercom systems.
I have a stash of them that will be used in a new preamp I am building, to really see if they are "extra special". They are designed to be non microphonic, are designed to be DC heated. The data also gives circuit values so there is no designing to be done ( at least to use as "specified" ).

Its an interesting subject to me, even though I am deaf as a post, but still enjoy grinding away at my vinyl collection, so at a later date I will see if I can add anything to the argument ( BUT after doing this for years I dont think I will find Nirvana !!! )

Joe

[TonyDuell]

I've seen 'audio' output valves in servo amplifier of the sort that were used in chart recorders, slit control in spectrometers, etc.

I certainly remember (but don't own) a chart recorder with a 6L6 in the servo amplifier. I've seen EL84s used in a spectrometer slit drive. I forget what are used in my 2 XY recorders but they are likely to be valves used in audio or TV (one is certainly American valves, the other is something like PCL82s -- yes, I remember they were 'P').

I remember seeing a crystal-controlled synchronous motor clock in the London Science Museum which drove the motor from a pair of EL34s

I've also seen regulated power supplies in instruments with EL34s and even PCL85s as the pass component.

So perhaps most of said valves were used in audio amplifiers but they do turn up elsewhere.

[Diabolical Artificer]

Found the CV4004's on ebay £254 for two! Or £282 for a pair of Arthurs, that's just plain bonkers. I can only assume these valves are coming from in the main old chaps stash's, judging from the various makes, no ones getting any younger, folks are cashing in.

Andy.

[Dave1000]

Old Mullards are indeed totally lunatic prices in the main - if anything £254 is on the low side - I have noticed 1950's valves, NOS, go for over double that and singles go for more than that.
The impression I get is that many come from estates (that is from people who have passed-on). 2-3 years back I was looking around a house that had all but been completely cleared/emptied, with a view to buying. The deceased owner had very obviously been a very keen radio ham (I hope that isn't a derogatory word here) - large mast in the garden etc., and on the bench of his workshop/radio shack (rear bedroom), was a small box of valves - I did not look what they were - and someone had put a note on them - "keep - valuable".

One or two collections of valves are also sold off, usually lot by lot - obviously collecting valves for their own sake has been a passion for some people over the years - somewhat different to collecting stamps or cigarette/trade cards I suppose, but whatever floats your boat.

Thanks again for the information on the power amp valves.

[Dave1000]

The other place that old valves come from are, almost unbelievably, long-forgotten stocks from sales and repair shops - remember those? When everybody rented their tellies?
Some traditional local stores, of all sorts seem to have just shut-up shop, closed their doors and been left. Over the past very few years I have bought what have obviously been very old hardware store or local tradesman stocks of things like screws and various fixings in unopened boxes marked with makers LONG since gone, for instance.

[m0cemdave]

Originally Posted by TonyDuell

I've seen 'audio' output valves in servo amplifier of the sort that were used in chart recorders, slit control in spectrometers, etc.

I certainly remember (but don't own) a chart recorder with a 6L6 in the servo amplifier. I've seen EL84s used in a spectrometer slit drive.

Esoteric audio valves (and EM34's) do turn up in test equipment and vintage bench power supplies. Sadly it often results in the equipment being bought just for those and immediately scrapped.
I have a couple of old chart recorders that use a pair of EL84's (Telefunkens, no less) in the servo amp. Some forum members have seen these - I've been trying to dispose of them for years at radio rallies with no takers, even after mentioning the valve content. I think the fact that they weigh 25kg each "outweighs" any interest from the valve freaks ...

[Radio Wrangler]

The reverse process is happening.

Real audio valves like KT66 and so on have become highly sought after and prices have surged to amazing levels.

So the audio aficionados have widened their nets to encompass any power valves that are similar, so TT21 are now sought after (RF version of KT88 with top cap anode. Nothing is safe. They are after anything.

On top of this there are people who can't afford the pundit hyped ones and they try anything they can get their hands on, then they post eloquent adjectives on the internet hoping to be the starter of the next fad tube!

I think only the EB91 and 6H6 might be left. anything with gain will have been grabbed.

David