"MY GLOWING RELICS: PART 2"

Yesterday I began an exhibition of the best 12AX7 tubes left in my thermionic collection.  Perhaps someday I will expand the list to include 12AU7 and 6SN7 types.  As for today, I will continue with 'Part 2' of my favorite 12AX7 still in my collection.  Also, I am going to throw in some bonus content (perhaps in 'Part 3') as I have some late 1940's General Electric/Ken-Rad 12AX7 prototypes that look suspiciously like the first to market RCA 12AX7.  Actually they look more like a hybrid of the two, and not always pretty as such!  Saving that for later, here goes with my next most favorite 12AX7 in my collection... perhaps the most underrated and unknown American made 12AX7.  The mid 1950's short black plate Sylvania 12AX7.  What a sublime sounding tube!

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"Discover the Crown Jewel of Mid-1950s Audio Tubes!"

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Sylvania is known for making
some of the very best audio tubes
of its era.  This tube is no exception.
The short black plate variant of the
Sylvania 12AX7 was produced in
relatively small quantities compared
to other 12AX7 tubes from the mid to late 1950's.  This limited production
​run contributes to its rarity.
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​These are becoming very, very difficult to find, and for good reason.  The audio quality is in the same league as the the tubes presented in Part 1 of this blog entry.  It is very, very close in quality to the venerable Telefunken ECC83.  If offered a Sylvania Long Black Plate of same era, assuming they are of equal provenance, I would always take the Sylvania short black plate.  It is that good of a tube.

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"In a tale of tubes and teamwork, CSF and La Radiotechnique created military magic, – talk about double trouble in the name of precision!"

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​In the mid-20th century, CSF (Compagnie Générale de Télégraphie Sans Fil) based in Saint-Égrève, France, and La Radiotechnique (a subsidiary of Philips) based in Suresnes, France, developed a closely knit relationship centered around the production of high-quality vacuum tubes, specifically the 12AX7S models, for military applications.  (See photo to left.. these are Philips La Radiotechnique French Military tubes made under contract for CSF.  I find it interesting they are labeled on the sales contract as both 12AX7S and 5751.) 

Both companies played significant roles in supplying the French military with essential electronic components. La Radiotechnique, identified by the military code FRS, and CSF, marked by the code FSE, collaborated extensively to meet the stringent demands of military specifications. This partnership was vital in ensuring consistency and reliability in the performance of their products.

A notable aspect of their collaboration was the identical construction of the 12AX7S tubes produced by both factories. Despite being manufactured in different locations, these tubes shared the same design and technical specifications. This uniformity was crucial for interoperability and standardization across military equipment.

The 12AX7S tubes often bore both the FRS and FSE military codes, reflecting the intertwined production processes of the two companies. Typically, the FRS code of La Radiotechnique was permanently etched into the lower part of the glass tube, while the FSE code of CSF was painted on the same tube. This dual marking underscored the cooperative efforts and mutual reliance between the two manufacturers.

The relationship between CSF and La Radiotechnique highlights a period of significant collaboration in the French electronics industry, particularly in the context of military production. By aligning their manufacturing processes and maintaining stringent quality controls, they ensured that their products met the high standards required for military use. This partnership not only facilitated the production of reliable and high-performance vacuum tubes but also exemplified the broader trend of industrial cooperation during an era of technological advancement.
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In summary, the partnership between CSF and La Radiotechnique was a model of industrial collaboration, driven by the demands of military precision and excellence. Their shared efforts in producing identical 12AX7S tubes, marked by both FRS and FSE codes, underscore the depth and success of their cooperation.

Oh, and did I mention?  These are some of the best sounding French tubes you can ever buy.  No they are NOT 'MAZDA' tubes, although you will see some major sellers call them as such.  MAZDA tubes are only properly made by British Thomson-Houston and French Thomson-Houston and their subsidiaries such as CIFTE.  Indeed, Thomson purchased shares of CSF in the 1970's, but they simply resold the FRS code Philips La Radiotechnique tubes as explained above, therefore they are not the same as the French MAZDA tubes that most people have in mind.  

​See the photos below.  These are RT 12AX7S through and through, with FRS Suresnes factory codes.  Resold by CSF, yes, but in this case not made at the CSF factory.  Which seems to hold true for all the ones I have found.  I have yet to find the reverse; a 12AX7S of this same construction with CSF FSE codes etched permanently into the glass, with FRS La Radiotechnique simply painted on.  But, the world of French tubes is pretty wild and not for the faint of heart!  They could exist, and if anyone has one or has seen one, please, please let me know.  

​If you want to see very similar in construction, yet ACTUAL CSF of St. Egreve made tubes, stay tuned.  They are next in line! (No La Radiotechnique codes to be found anywhere on these!)

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"a sPECIAL french csf tube"

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After spending quite some time on the intimate relationship between French CSF and La Radiotechnique tubes, we finally come to a CSF tube, while retaining much of the apparent construction technique of the French Military 12AX7S, actually branches out on its own it seems as a unique CSF tube. 

This is an extremely rare French tube, with some truly gorgeous black plates, and I must brag on the tremendously well preserved silkscreen as well.  

This is an outstanding audio tube with a unique warm sound.  One must truly experience it to understand; unfortunately it's among the rarest tubes in the world, at least as best I can tell.  I have never seen another pair like it.  

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stay tuned for part 3....