oldest tube(s) in your system

Please let us know what they are running in too. Thank you for your attention to this matter...ha!

2 x 1949 Sylvania ladder plate 6BL7GT (in monoblock amps, custom built 2 x 6BL7GT + 4 x KT77)

xenolith09-10-2025 1:28am

noromance Details Discussions Posts This discussion Message User 10,210 posts 09-10-2025 at 02:57am Copy Comment URL Report Comment Edit Delete Oldest tube in use... I guess the RCA 5693 from 1948. I use them in a Lambda 25 power supply to supply regulated 325volts to a slightly modified Croft Micro 25R preamp.
pindac Details Discussions Posts This discussion Message User 3,325 posts 09-10-2025 at 03:11am Copy Comment URL Report Comment Edit Delete RCA Grey Glass Hamburger Font 6SN7 - 1940's Production Measured at my end by a friend and both close matched near Factory Spec's. I have other pairs of Valve Types all matched near Factory Spec's. from the 50's and 60's Production Era's
xenolith OP Details Discussions Posts This discussion Message User 196 posts 09-10-2025 at 03:13am Copy Comment URL Report Comment Edit Delete @noromance Beautiful piece of gear! Thanks for sharing the photo. Love the eye tube too! Does it ’close’ (or is it open?) at 325v?