Vacuum Tubes

[William Layer]

On Sun, 27 Mar 2005 00:30:31 -0700
"Bill Machacek" <bmachacek at pcisys.net> wrote:

> Just thought I'd let the listees know that while visiting my local parts and equipment store today (which carries a large amount of discontinued and surplus items of all types), I noticed there was a whole aisle of electronic vacuum tubes there. 

As several others may have pointed out, you really need to know what you are buying whem it comes to old vacuum tubes. Most of the TV & Radio types were produced in legion, and plentiful stocks remained after the parts were obsoleted.

The primary markets for vintage tubes, are fourfold:

 1) Audiophiles, seeking rare manufactures of common types of audio tubes.
 2) Antique radio enthusiasts, seeking hard-to-find types for old radios; manufacture can be of great interest, but less important to those who just want to get a piece working.
 3) HAM enthusiasts, seeking hard-to-find and common types for RF power amps.
 4) Repairers or enthusiasts of old instrumentaion / control / lab equipment, seeking generally common types of various manufacture.

Having worked with, built and repaired tube equipment for over a decade, I can tell you that you really need to *know* what you are looking at when buying old tubes. The minutia are on a par with, but not quite as historically involved, as Japanase (Nihonto) swords. A small suitcase can literally hold either a fortune (might as well be crisp $100 bills) or be a suitable boat-anchor.

As a sidenote, factory tube production went on up until the late 1980's or early 1990's in the USA, mostly for military contract use. Some of the tubes made during this late era were close to the best ever of their types.. I can think of the JAN/PHILIPS 6SN7GTA and 5814A as examples.

Military tubes however, can be a real canard for the audiophile. Most people assume that a 'military grade' tube will be superior in audio performance to a similar civilian type; nothing could be further from the truth. As examples, the military types 6189 and 12AT7WA compare to civilian 12AU7 and 12AT7 respectively; but as audio tubes, they sound totally dreadful - literally, like breaking glass. In these lines, the term "JAN" refers to "Joint Army-Navy".

On the converse, the afforementioned 5814A and 6SN7GTA compare to 12AU7 and 6SN7 civilian types, and are exceptional devices in terms of sonic performance. You can never tell until you sit down and objectively listen to them.

Yep, I rambled.

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   -. William W. Layer .- -. St. Paul, MN USA .-
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-. Cheif bottlewasher, Atma-Sphere Music Systems .-
        -. http://www.atma-sphere.com .-
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