There are only 2 major manufacturers of vacuum tubes in production today that are available for electric guitar and bass amplifiers.  Many other companies "relabel" these tubes with their own logo, but a few of them like Tube Amp Doctor, ARS, and Mesa Boogie do extensive testing and matching before boxing and shipping to the customer. 

1.  The JJ/Tesla plant founded in Czechoslovakia, has been around since the 1920's but are now building in the Slovak Republic.

2.  The Xpo-pul plant in Saratov, Russia, builds for Mike Matthews, CEO of Electro Harmonix.  He has the rights to Sovtek, Tung-Sol, Genelux, Electro Harmonix, Svetlana, and Mullard.