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24.156.56.143
Hello to Tube Asylum aficionados. I have been researching info on a tube I have. It is a labeled RCA but is certainly Heerlen made Phillips 12ax7. This sight has some discussion on similarly marked tubes.
I am just trying to get some confirmation on the year date. Under tube between pins is stamped Delta 8 then mCB. Has welded plates too.
I will post pics.
I have it listed on eBay and assume it is 1953 but trying to get more info would be great. Thanks Merry Christmas!
http://i227.photobucket.com/albums/dd121/mazzone-clementi/IMG_3464.jpg
http://i227.photobucket.com/albums/dd121/mazzone-clementi/IMG_3456.jpg
Edits: 12/27/14 12/27/14 12/27/14Follow Ups:
I have included some reference photos taken from past eBay listings to clarify the differences between Copenhagen and Heerlen production for 12AX7/ECC83 tubes.
The first and second photos above show the triangle symbol inverse to your tube (photo 3) - almost a mirror image that represents Copenhagen production rather than Heerlen production.
As you have correctly stated in your eBay listing your RCA 12AX7 tube was made in Heerlen Holland (photo 3) in October 1953. The RCA 12AX7 tube shown in photo 1 above was made in Copenhagen Denmark in September 1953 and the RCA 12AX7 tube shown in photo 2 above was also made in Copenhagen Denmark in January 1951. I don't think the January 1951 date code is correct. I am more inclined to think the tube in photo 2 was made very early in January of 1954 but was tagged with the year of manufacture as 1953. Being a Copenhagen produced tube it could have also been made back in January of 1951.
I hope the above information helps.
The triangles can be confusing, especially with old code non acid etched print. Sometimes other clues help identify origin. I don't believe welded long plates were made in the Heerlen factory for ecc82 and ecc83. Other clues such as plate construction suggests Copenhagen origin. However their were welded plate ecc81 Heerlen tubes made in the early fifties with old codes which are often mistaken for Copenhagen. It seems the reverse practice for welded vs crimped plates were in practice for ecc81 tubes. Early fifties Copenhagen ecc81 were however crimped plates ! Go figure.
The ultimate test is to audition the tube for factory sound. A reference tube would be helpful. A Copenhagen should have better resolution especially in the mid range. A Heerlen has more extended treble but overall less resolving. The old code Heerlen also has a liquid more euphonic sound to the Copenhagen making it very appealing especially with female vocals, but ultimately less transparent to the Copenhagen.
Very Helpful XLR!
Straight up triangle is Phillips Copenhagen.
That said, this is the first I've seen the codes on the bottom glass from Phillips/Amperex. I've always seen the codes acid etched in the glass in the area of the bottom mica.
IIRC, Siemens and/or Tele codes them as such.
Cheers,
W
The codes on the bottom of glass were used by Philips factories from 1950 -1956. The Philips new codes were acid etched on the side of the tube from around 1956 onwards. Philips old code dates require a lookup table to decipher manufacture dates. The more familiar new codes follow the factory , year, month numbering system.
Looking right at the Phillips factory valve codes manual, there's the FM/TTC and so on, at the bottom of the glass.
Thanks for the correction.
Cheers,
W
I am convinced by the shadow of a doubt, that you are discussing Philips, not Phillips. Please be advised and alter your editor functions. Since these tubes are so dear, I don't even look into buying until recently. I acquired a few tubed headphone amps and their power tubes. I am an inveterate tube roller and heard how much better they sounded with rolled tubes so I broke out my 16 Y.O. stash and made some subs very quickly, with good results but didn't have a lot of the subs for the power tubes . So... I on the hunt again.
As an aside I am surprised what a tube sellers maker up is on a single tube. E.G. a Metal based nos testing in original box, 6SN7W give you $30 but charges over $300 for the same tube while retaining the option to sell it back to you. A true story I kid you not.
I will have to sell privately.
Steve
I believe this tube is from the Copenhagen factory. Both Copenhagen and Heerlen factories have utilise triangle symbol and sometimes its difficult to distinguish. The Copenhagen triangle is more equilateral. Heerlen is a right angle triangle. Also the welded long plates from early fifties suggests Copenhagen origin.
Thanks for your help. I thought that the Copenhagen triangle would be oriented pointing up and the Heerlen is oriented with the right angle back to the month code(8)?This looks to me to be a right angle Heerlen from 1953.
The welded plate is give away Copenhagen. I don't believe Heerlen made welded long plates. However, the orientation of the triangle can vary making identification confusing. The plate structure also looks like Copenhagen. This offcourse is good news since Copenhagen is a superior tube to Heerlen as a factory type.
The final discriminator of a tubes origin is to actually hear the tube. That will definitely identify Copenhagen or Heerlen. Offcourse a reference tube would be useful in such a comparison or a familiarity with the sound of the factory in question.
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