VTV Vacuum Tube Valley - Dual Triode Characterizer (Tube Tester) Ser. # 006 Photo #1308456 - UK Audio Mart
Vacuum Tube Amplifiers: George E. Valley, Henry Wallman: 9780486614076: Amazon.com: Books
VACUUM TUBE VALLEY: 90's and 00's tube technology
Audio Video Choices - All issues of Vacuum Tube Valley Magazine are available for free download: https://web.archive.org/web/20130604042043/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/vtv.htm | Facebook
Silicon Valley Was Built On Tubes Of Glass | Hackaday