Early 1960s Valvo Hamburg production - The real King of Bass - Unparalleled musicality with substance and weight in midrange presentation
Date code: 8Y2 D4A3 (D = Hamburg, 4 = 1964, A = January, 3 = 3rd week of the production month)
GM (Mutual Conductance) test result: 100% NOS
Silkscreen: 100%
Special feature: Red number "5" on bottom - Ultra RARE
Packaging: Original Siemens EF 86 tube box
Professional Tube Testing
NO shorts, leakage or gas. NO noise or microphonics.
This tube tested Strong NOS (110%+ mutual conductance value for NOS/NEW) on a reliable Mercury 2000 tube tester with the following result (mutual conductance both in uMhos and in percentage of NOS/NEW value):
2,200(110%)
Good tubes start at 1,200 and new tubes (incl. NOS/NIB) 2,000, and the Mercury 2000's rated mutual conductance for new EF86 tube is 2,000. Test result can also be seen in the pictures. In case you wonder what all these numbers mean to your sound experience, it's actually quite straightforward: mutual conductance directly translates to a tube's ability to amplify sound, so the higher the numbers the better.
