Unparalleled sound characteristics and superb build quality - True holographic sound stage with layered details and ultra clarity
Date code(s): U4104906 (U = Ulm, Germany, 4 = 1964) and U6114106(U = Ulm, Germany, 4 = 1964)
GM (Mutual Conductance) test result: 95%/86% NOS
Silkscreen: 100%
Packaging: NEW reproduction Telefunken boxes
Professional Tube Testing
NO shorts, leakage or gas. NO noise or microphonics.
The two tubes tested Near NOS (90%+ mutual conductance value for NOS/NEW) and Strong NOS (110%+ mutual conductance value for NOS/NEW) respectively, on a reliable Mercury 2000 tube tester with the following result (mutual conductance both in uMhos and in percentage of NOS/NEW value):
Tube 1: 1,900 (95%)
Tube 2: 1,750 (86%)
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.
