Skylab
Reviewerus Prolificus
http://vacuumtubes.net/ will sell you a single NOS 5998 for $85. Not cheap, but if you only need one...
Amazing how those have gone up. 3-4 years ago that same seller sold 5998's for $20 each.
Amazing how those have gone up. 3-4 years ago that same seller sold 5998's for $20 each.