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Mullard’s Empire of Rust…

…Or iron oxide if you happen to be a chemistry boffin. The photograph on the left was taken on the north-east boundary of Mullard’s Crossens factory in Southport. Although the Crossens works didn’t manufacture vacuum tubes, it did produce ferrite pot cores and magnets for loudspeakers, motors, telephones and cathode-ray tubes (television and oscillsocope screens) and was one of several Mullard ‘feeder’ factories situated in the north of England. These feeder factories supplied electrode sub-assemblies and other specialised components to Mullard’s mighty Blackburn facility in Lancashirewho subsequently utilised them in the fabrication of vacuum tubes.

Back in the day, the Crossens works was home to dozens of red-brick workshops (built in 1907), which were packed closely together on the site just like in those paintings of urban industrial landscapes by Lowry. Mullard took over the site from Vulcan Motor and Engineering Co. in 1955 and the workshops became home to specialised mills, presses, kilns and bespoke tooling for grinding powders, making pastes, baking, shaping and machining the magnets and ferrites.

Manufacturing magnets was dirty work, but it did create jobs—Mullard were one of the town’s largest employers of engineers, technicians, assemblers and all kinds of skilled craftsmen, and frequently advertised positions of employment nationally in magazines such as ‘New Scientist’. They also employed accountants, typists, secretaries and other admin staff whom were based in the relatively modern building (constructed by ‘Philips’ in the late 1950s) on the west border of the site running along Balmoral Drive.

When I found the Crossens site I realised I’d left my visit very late in the day—the old red-brick workshops were gone. They’d been demolished, the kilns removed, surely scrapped and the people that once worked there with their knowledge and expertise were gone too. The site was just an empty, derelict, concrete space where buddleia and willowherbs were growing amongst the scattered rubble and broken masonry. Only a small part of the main admin building still remained standing, waiting for the time that was soon approaching when it too would be swept out of existence, making way for yet another bland, nondescript housing estate.

mullard_southport_derelict_320px — Mullard Crossens site, Southport, Lancashire – Photograph taken August 2017

I can’t help but wonder at the lack of vision of our local councils and government—have they given any thought to how all this will ultimately play out for once Great Britain? What kind of nation will Britain be when there is no longer the challenge and excitement of manufacturing, engineering or scientific jobs to inspire young minds, when the dream of taking pride in something greater than oneself has faded and when a large proportion of the population dwell in little boxes made of ticky-tacky watching reality television… But this isn’t the place for such wistful, nostalgic ramblings—we’ll leave that to the poets and politicians—our quest is the search for better guitar tone. So steering back to topic…

Although the musician in me appreciates that a huge amount of what we consider to be great guitar tone comes from the head and the fingers, the hard-core engineer in me understands that there are factors in the inner workings of guitar gear that improve the chances of realising that elusive tone. But what are those factors? Well, as the reader is probably aware, I’m strongly of the opinion that tubes, the component in a guitar amplifer that does the work of shifting electrons around is a factor, if not the key factor. After all, there must be something in why these archaic, hot, high-voltage devices persist despite the advent of more convenient, less costly technologies. And not a decade passes without some new technological development emerging, such as op amp, JFET, digital modeling, profiling, tube-on-a-chip, FET-in-a tube, etc all claiming to deliver the magical sound of tubes. Yes, there’s definitely something about tubes that works wonders for electric guitar tone, and this is why I remain fascinated by what makes a good tube and Mullard, who were renowned for making exceptional tubes.

It crossed my mind to try and clamber over one of the Crossens site fences or crawl under one of the gates to make a closer examination of the site, but Mrs E. would certainly not approve. She’s now getting wise to my requests to go on short holidays to industrial northern towns such as Southport, Fleetwood and Blackburn and trespassing might be taking things one step too far. Besides there really was nothing left to see. Only the remnants of the Philips admin building and, once they were levelled and the new houses built, nothing would remain to tell the tale of the part that Crossens played in Mullard’s fantastic golden age in electronic manufacture, when British audio ruled supreme.

Sadly, all the ex-Mullard factory sites are now either derelict or have been built over. For instance, the Fleetwood works, which did manufacture tubes, has been completely erased from existence. Not all is lost though. Part of Mullard’s legacy still survives in the vast library of technical documentation, handbooks, manuals, bulletins and books they published during the long course of their operations. A few of these texts hint at the processes and techniques Mullard developed and refined over the decades, their research endeavour to exceed existing engineering limitations and scale new heights in what could be achieved with thermionic technology to build a better vacuum tube. The brief excerpts below, from one of Mullard’s technical publications, ‘British Special Quality Valves and Electron Tube Devices Data Annual 1964–65 by J. Mackenzie Robertson and G. W. A. Dummer’ gives some insight into the complexities and subtleties of tube design and fabrication. For instance, Mullard made the decision to manufacture the nickel, and other, alloys (that’s right, Britain didn’t just manufacture the World’s finest steel alloys) that went in their tubes on site, that way they could exercise complete control of the quality of their processes as described below:

mullard_techincal_publication_320px — Technical Communication: one of Mullard’s myriad of technical publications.

The cathode is formed from a thin-walled tube of at least 97% nickel, the remainder consisting of controlled amounts of impurities and of additives which are beneficial to the performance of the cathode. Each possible type of impurity has its own maximum controlled level and the total of the impurities does not exceed 0.4%. The outside of the tube is sprayed with a suspension of barium-strontium-calcium carbonate. The purity, and the crystalline size and shape of these substances are closely controlled.

And in this extract:

The electron emission from the cathode depends on the relative quantites of the different carbonates in the coating mixture, on their crystalline size and shape, and on the changes they undergo during the subsequent processing and operation of the valve. In particular, the emission depends on the concentration and location of the positive barium and strontium ions in the coating, derived from the barium-strontium oxide layer after heat treatment to reduce the carbonates to oxides. The most important factors affecting emission are the chemical composition and operating temperature of the cathode nickel. The impurity content of all nickel used in Special Quality Valves is known to an accuracy of one part in a hundred thousand; and furthermore each batch of nickel is tested before being used, by means of a preproduction run on several types to confirm cathode performance.

And this extract reveals something of the art of grid winding:

The winding tension of the grid wire [ed: ten micrometres (microns) in diameter, which is thinner than a human hair] is important, since the grid may be at a temperature of about 400°C during normal operation. Under these conditions, thermal expansion of the grid wires must not produce slackening [ed: resulting in microphony]. On the other hand, the tension must not closely approach the breaking strain of the wire, which may be as low as five grammes. The winding tension is controlled by a specially developed technique which measures the tension of each individual turn of completed grids.

Fascinating stuff, eh. To all intents and purposes it’s rocket science—the real engineering behind better tube tone. Modern marketing efforts, such as the promise of improved tone through cryogenic treatment of tubes or tube rebranding seem terribly misguided, even crass in light of these few excerpts written all those years ago by Mullard scientists and engineers. And this book is just one of Mullard’s commerically available texts. Their specialised manufacturing processes for efficient, quiet cathodes, alloy formulas, and other tricks of the trade were closely kept, patented secrets and that information was not for general release. This knowledge resided in technical documents filed away in cabinets contained within the walls of Mullard’s building premises, in the minds of the scientists and the hands of skilled workers, some of which devoted their entire lives to the art. Many of those people are no longer with us and I wonder if any the technical documentation survives—maybe a few of the papers are gathering dust in the darkness of some old boy’s attic or perhaps they ended up in the archives of Philips Research Eindhoven, waiting for a time when tube manufacture becomes a commerical reality again. We can but dream. Until then, for me at least, the real quest for tone lies in the art of engineering tube circuit designs and the quality of materials and techniques utilised in the fabrication of tubes.

derelict_philips_admin_building_august_2017_640px

My last fleeting impression of the Crossens site was of a smart, entrepreneurial looking fellow wearing Chinos and light coloured shirt, RayBans balanced on his head. He was standing next to a silver, open-top sportster parked by the main works gate holding what seemed to be documents or plans in his hand. Possibly he was a developer undertaking a site inspection or perhaps an investor. We sped past him along Balmoral Drive leaving the last few tattered remains of Mullard’s once glorious and proud empire behind us.

She was glorious
She was proud:
Passed by side
And knew already
That which she
Had taken
From me
From my glance
From my stare.
As she passed
By my side
She had the glory
She had the pride
—B.A. Taylor

On 20th November 2014 the ‘Southport Visiter’ published a short news article containing photographs (taken by Peter Langfeld) of the Crossens site being demolished: Meols clock tower demolished after years of decay

This article is one of a growing library of historical and technical papers published by Effectrode. If you’re interested in the real story behind guitar tone—no marketing hype, just in-depth, esoteric stuff you won’t find anywhere else online or in print, the facts about what is genuinely relevant to equipment and recording technique—then you might want to take a look at our library here.

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Mullard’s Empire of Rust…