Help ID tube

[Travis]

I have a box thaty says 12ax7 1991 China NOS. My friend said it was red dragon or gold dragon (he doesnt remember which). It is last tube on right and the top part, i dont know what that part is called, is square as opposed to the normal round type. Not sure if you will see that from image:

http://img131.imageshack.us/my.php?image=12ax7tubesfw9.jpg

All the others i switched around a few times and kind of really like the chinese tube in V1- first gain stage- sounds like complete opposite of 5751.

Thanks.[/url]

 

[212Mavguy]

Those gold dragon 12ax7 type tubes are most likely made by Shuguang in China. Shuguangs come in all sorts of private label brandings. This is definitely chinese manufacture, most likely shuguang.

The part you see and describe in the top that is a square shaped cup in shape its called a cup style getter, actually a bit of a misnomer, what you are seeing is a relic left over from its one time use during manufacture of the tube. Some are circular, referred to as halo style, (most common,) some are rectangular, (Sylvania vintage long blackplate) some are D-shape, (early Philips owned tube companies like amperex, siemens, mullard, philips miniwatt 12ax7 used "d-getters") some have a curious windmill shape, (the legendary Raytheon 5751), at one time each getter holder held a small pellet of material that was heated up to around 1600 degrees farenheit after the tube was vacuumed out, the result is that silver colored flashing that sits opposite of it most commonly in the top of the bottle, that is the real getter, its function is to absorb any gas molecules emitted by the tube parts during warmup, operation, and cool down.

The Brimar tube on the far left is a real sweet vintage item, and is prized by many for the kind of clean and overdriven tone it produces, particularly bluesy tone. If strong and not microphonic, it commands a used resale value on ebay worth at least as much as three or four of any of the other tubes in that pic together. Best of luck to you.