Mullard Blackburn new tube launch postponed

[stevesuk]

The latest from Mullard at Blackburn UK.
Hi there,

It’s now been three months since our last notice and activity has been frantic and very productive but as yet the elusive solution is not quite ready for public unveiling. Despite the economic downturn our drive to launch the new TechTube™ valve technology is not diminished. We still have full management backing and are getting closer to the specification we have set ourselves.

Our target for the E813CC valve is to have every triode and consequently every valve with an Ip current within a band from 0.8mA to 1.2mA. We targeted this band after benchmarking several competitor valves. The benchmark analysis showed that current valve production has Ip ranging between 0.7mA and 1.6mA, even though the data sheet specification is 1mA! Within a valve, the triode to triode variation ranges from nothing (both triodes having the same output) to 0.5mA difference between triodes.

NOS valves perform better having Ip varying between 0.7mA and 1.3mA. Mullard NOS (Blackburn production) have excellent within valve (triode to triode) variations of less than 0.1mA against a norm of 0.25mA. Sovtek have a slightly wider triode to triode variation of 0.25mA but valve to valve they are very consistent with all the valves we tested falling between 0.95mA and 1.4mA.

Currently, our Ip ranges from 0.75mA to 1.5mA, too much variation considering our claim that we are benchmarked against the Blackburn Mullard valve. We continue to work on the factors that give this variation and are near to a resolution.

The other characteristic that we needed to improve upon according to feedback from the September show is microphony. Again we benchmarked several valves already in the field, both current production and NOS. Once again the variation seen was incredible. It’s no wonder end users complain about inconsistent performance!! Over the months the team has been working on this problem, we have come to know how valves shake, rattle and role in intimate detail. Our use of high speed cameras, differing construction techniques and numerous mechanical designs has led us in several directions. Unfortunately even though most were successful in removing microphony they created problems with other characteristics of the valve and consequently they have been scrapped. The down side of this process is that time moves on. Our knowledge base is rapidly increasing but that elusive solution that can be industrialised and automated is still to be found. We continue with numerous parallel paths and the team continues to work hard.

As a result of these factors we will not be in a position to launch the web sales to our plan of April this year. The team continues to work hard on the problems and we will keep you informed as we move through April and probably May.



From all in the TechTube™ team @ Blackburn
.


Steve UK
www.valvepower.co.uk

[Phil_S]

Heck, I can't understand why they don't just replicate the old Mullard formula and produce *exactly* that. I assume they've got access like no one else does, to the trade secrets. I realize, the Mullard name has been sold, but the public isn't so easy to fooled. If they could simply pull this off, it would rock both the guitar amp and audiophool communities. It makes me wonder about the business plan that holds out for unobtainium. I guess we shall see.

[Alexo]

Thanks for the update, Steve.

Reminds me of a joke:

A woman walks into her lawyer's office and says she wants a divorce.

The lawyer asks: "On what grounds?"

The woman: "The marriage was never consummated." -

"Never?"

"No, my husband is in IT - he just sat at the edge of the bed all night and talked about how great it was going to be!"

[leslie]

Heck, I can't understand why they don't just replicate the old Mullard formula and produce *exactly* that. I assume they've got access like no one else does, to the trade secrets. I realize, the Mullard name has been sold, but the public isn't so easy to fooled. If they could simply pull this off, it would rock both the guitar amp and audiophool communities. It makes me wonder about the business plan that holds out for unobtainium. I guess we shall see.

Thorium
http://en.wikipedia.org/wiki/Thorium

The emission from thin films of thorium deposited on to titanium and tungsten has also been studied. The emission from a layer on titanium that had been thoroughly pre-cleaned was found to be much less than that from a similar layer on tungsten.

The application of these results to the suppression of grid emission in the presence of thoriated tungsten cathodes in transmitting valves is discussed.

Print publication: Issue 2 (February 1959)
Received 23 October 1958

large tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates from the wire surface, while new thorium atoms diffuse to the surface to replace them. Such thoriated tungsten cathodes deliver lifetimes in the tens of thousands of hours.

Barium Oxide
http://en.wikipedia.org/wiki/Barium_oxide
Cathodes in small "receiving" tubes are coated with a mixture of barium oxide and strontium oxide, sometimes with addition of calcium oxide or aluminium oxide.
http://en.wikipedia.org/wiki/Calcium_oxide

[Mr_dB]

Pictures I've seen of the new Mullard small-signal tubes are very strange. They appear to have re-designed the dual-triode almost from the ground up, although it still fits in the same socket and glass envelope. Inside the tube it looks like two little metal cans sandwiched between a pair of mica washers, it almost looks like someone stuffed a pair of Nuvistors in there.

They're not looking to recreate the past, but to actually attempt to advance the art. I see it as being more interesting for hifi than guitar amps.

[zaphod_phil]

Yes, they're definitely trying to take the technology forward again. And I agree that they seem to have been primarily targeting the hi-fi and recording studio markets. However, this sudden need for low microphony suggest that maybe some of the guitar amp manufacturers got talking to them. And who knows, these tubes may turn out to sound killer in a guitar amp. I think they're going to be expensive, though....

[Chubsman]

Like pharmaceutical companies... they will have to pay for all the research and development... So not $9.99 pre tubes for sure...

[Mr_dB]

Yes, they're definitely trying to take the technology forward again. And I agree that they seem to have been primarily targeting the hi-fi and recording studio markets. However, this sudden need for low microphony suggest that maybe some of the guitar amp manufacturers got talking to them. And who knows, these tubes may turn out to sound killer in a guitar amp. I think they're going to be expensive, though....

I saw some numbers bandied about, $99.95 seems to ring a bell, although I don't remember if that was each or for a pair.

[dotfret]

They have problems - that costs them money, which is their problem. Some of these valves are definite goers, some are a bit off, and they are not selecting out the good ones and discarding the bad ones.

The great challenge to modern manufacturers is to produce something that sounds like the "old stuff" without using Thorium. Most of the modern production sounds "too crunchy" in a valve amp, as far as I am concerned.

The obvious conclusion is that they care about what they sell, and they are not going to sell anything dodgy. When they do get to the market, I would be confident that the products are worth buying.

[zaphod_phil]

AFAIK Thorium was only used in directly-heated radio transmitter valves, which had thoriated tungsten filaments. Run of the mill indirectly heated audio and RF valves use such things as mixtures of barium and calcium on their cathodes, without any thorium being involved.

[novemberrain]

Our target for the E813CC valve is to have every triode and consequently every valve with an Ip current within a band from 0.8mA to 1.2mA. We targeted this band after benchmarking several competitor valves. The benchmark analysis showed that current valve production has Ip ranging between 0.7mA and 1.6mA, even though the data sheet specification is 1mA! Within a valve, the triode to triode variation ranges from nothing (both triodes having the same output) to 0.5mA difference between triodes.

Currently, our Ip ranges from 0.75mA to 1.5mA, too much variation considering our claim that we are benchmarked against the Blackburn Mullard valve. We continue to work on the factors that give this variation and are near to a resolution.

I've seen this again and again during PPAP. Run the process, numbers look bad, scratch head, repeat. Scratch head some more.

What they need to do is literally dig up some old engineers. Salvage some usable DNA, clone some fresh replicas of the old engineers. Then tackle the problem...

Everyone knows everything good in the U.K. is made by blokes in sheds. "Design process" meant "sketched out on a napkin over a pint". I'm not kidding, that's the way it was traditionally done.

Near as I can tell the original tooling from Blackburn spent its twilight days churning out tubes somewhere in India. One would hope they coated it in cosmoline and warehoused it...

[dotfret]

The thorium in a directly heated cathode is usually a component of the filament alloy, but traces of thorium oxide help emission from indirectly heated cathodes, which have a coating composed mainly of alkaline earth oxides (oxides of calcium/barium/strontium etc).

Mostly, cathode coatings are "trade secret", but what is not so secret is that a small amount of a "reducing element oxide" in the coating helps emission. Besides thorium, I know that magnesium, zirconium, chromium, titanium, uranium, and niobium oxides have all been tried at one time or another. What is in current use I do not know.

[novemberrain]

But let's talk about the "secret sauce" shall we?

We are of course talking about Blokes in Boiler Suits. Blokes in Boiler Suits built the British Empire on a nuts 'n' bolts level. Where pooftas in lab coats fail, Blokes in Boiler Suits labor on to victory!

To properly maintain sharp focus said Blokes shall commute to work on ponderous British motorbikes, a Panther pulling a fully enclosed Watsonian will do nicely. The rhythmic thump of a laboring British single emulates the heartbeat heard in Mum's womb, it stimulates creative thought. Further, any sod used to the inscrutable workings of Lucas electrics is fully capable of mastering all sorts of machinery. Any bloke sporting a Lucas magneto and still arriving at The Works on a regular schedule is surely up to the task!

Blokes in Boiler Suits have accomplished far more urgent tasks with bombs exploding all around...

[Shottky]

But let's talk about the "secret sauce" shall we?

We are of course talking about Blokes in Boiler Suits. Blokes in Boiler Suits built the British Empire on a nuts 'n' bolts level. Where pooftas in lab coats fail, Blokes in Boiler Suits labor on to victory!

To properly maintain sharp focus said Blokes shall commute to work on ponderous British motorbikes, a Panther pulling a fully enclosed Watsonian will do nicely. The rhythmic thump of a laboring British single emulates the heartbeat heard in Mum's womb, it stimulates creative thought. Further, any sod used to the inscrutable workings of Lucas electrics is fully capable of mastering all sorts of machinery. Any bloke sporting a Lucas magneto and still arriving at The Works on a regular schedule is surely up to the task!

Blokes in Boiler Suits have accomplished far more urgent tasks with bombs exploding all around...

I'm not sure if you're trying to talk about tubes or merely start a class war, but it would be unfair at best to say that "pooftas in lab coats" contributed less than those in "boiler suits".

I'm particularly interested in the materials that were used in construction during the original production runs versus those that the modern engineers are trying to use.

So Thorium is out. Anything else that they used to use that they can't nowadays? (Besides Barium?).

[zaphod_phil]

I would assume Barium would still be allowed, as long as it wasn't a radioactive isotope of Barium. What is important for cathode materials is the electron shell energy levels, so that electrons will be easily emitted with some applied heat, which is where materials like Calcium and Barium come in.

[novemberrain]

I'm not sure if you're trying to talk about tubes or merely start a class war, but it would be unfair at best to say that "pooftas in lab coats" contributed less than those in "boiler suits".

It's a metaphor and I'm semi-serious.

Back in the day engineers were well capable of clamping a chunk of stock into a vice on a Harrison and fabricating a part or a fixture as necessary. The line between a fitter and an engineer was blurry. The current crop of engineers are adept at pushing a little arrow around a CRT but besides developing a CAD program it's more a wish and a prayer that everything fits and works correctly in reality. Simply contrast the high degree of precision that was routinely achieved with relatively crude tools (original Blackburn production) and the lesser degree of precision (measurable in terms of consistency) in current Blackburn PPAP batches. One might deduce that we've lost something along the way. It doesn't matter what the materials are if they're incapable of consistent production.

[dotfret]

Zaphod - you are right, barium is toxic - but you would look a trifle silly if you forbade the inclusion of barium in the cathode coat, considering that the getter contains about a gram of barium! Indeed, part of the reason that the cathode coat functions so well is that there is a trace of barium vapor in the envelope.

The cathode coating is formed from a mixture of carbonates (thorium would be added as the nitrate) and applied as a varnish. The varnish base is guncotton, which "burns perfectly" (even without oxygen it forms carbon oxides and nitrogen on heating, and leaves no residue). When the varnished-on coating is heated in the "magic way"(presumably by a man in a boiler suit with a bone through his nose), the varnish disappears and an oxide coating remains on the cathode. BaCO3 = BaO + CO2, is the simple way to put it, but why it does not then fall off the cathode is the magic!
During the magical conditioning process this oxide coating, which should be an insulator, is transmogrified into a semiconductor, otherwise it would not do anything. Some of that barium oxide is reduced to metallic barium in the conditioning, and that is why the coat conducts.

What little I do know is that the "reducing element" should have a similar ionic radius to the metal in the oxide, and that the oxide coat would be depleted of barium if not for the "getter vapor". And I understand that there are tiny particles of nickel in the coat, too - but finely divided nickel will burn spontaneously in contact with air.

I also know that this black art was why the Philips group used to ship out cathode assemblies from Blackburn to Australia in special sealed containers - which was originally a Hungarian trick, Tungsram used to ship cathode assemblies to England before WWII. When Mullard were running the British Tungsram factory during the war, they must have learned something.