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Tubes, old and new

I sat down next to Tim Pavaracini in a room at T.H.E. Show in Irvine weekend before last, and listened to him talk about tubes. He told me that in the 50's and 60's the various tube companies would swap tubes amongst themselves when they ran low of a certain model, putting their own logo on the glass of a competitors tube. It would therefore behoove tube enthusiasts to learn the internal physical characteristics specific to each make, especially when spending big money on them. Tim's personal favorites are Mullards. He had nothing good to say about ANY tubes being manufactured today, feeling the guys and gals on the tube assembly lines have not apprenticed long enough to learn the skills necessary to build a quality tube, that they are not career professionals, but merely temporary employees. Buy your tubes from an honest, knowledgeable tube vendor!
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Showing 2 responses by tomcy6

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tomcy6
2,532 posts
 
Yes, back in the heyday of tubes manufacturers put their labels on tubes made by someone else, but it wasn't with bad intent. Tubes cost a couple of bucks back then and most people didn't care if they had an RCA or a Mullard in their tv or radio.

It's not too hard to determine what tube you actually have these days.

Phillips tubes (Amperex, Mullard, Siemens, Valvo and many more) have codes etched into the glass. A list of the codes and how to read them can be found here:
http://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf

Telefunkens have a diamond molded into the glass at the bottom between the pins and RCA etched an octagon around the tube variety (e.g. 12AX7) into the glass near the top of the tube for a couple of examples of identifying characteristics.

The Tubemonger has a huge library of photographs of vintage tubes that is very helpful in identifying tubes.

Of course, scammers have found ways to counterfeit many tubes and there can be subtle differences between a top shelf tube and its low shelf relatives, so it is best to buy from a reputable dealer rather than try your luck on ebay, probably cheaper in the long run too. A good dealer has a lot of experience that is invaluable.

I do enjoy learning about tubes and their various qualities, though.
tomcy6's avatar
tomcy6
2,532 posts
 
You're welcome Bdp24. You are most likely to see Phillips tubes with the "New Code" etched into the side of the glass near the bottom (top drawing at the bottom of page 3), using the top two "Examples of "correct code" format." So you can skip all the stuff about the "Old Code" and other code formats. It's not too hard to figure out the codes but if you have any questions feel free to ask me.
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