Warm, musical and euphonic tone plus the romantic French flavor
Date code: BY5 F1I1 (BY5 = EF86 production gen #5, F = Suresnes, France, 1 = 1961, I = September, 1 = Week 1 of the production month)
GM (Mutual Conductance) test result: 111% NOS
Silkscreen: 100% silkscreen
Packaging: Original Valvo EF86 tube box
Professional Tube Testing
NO shorts, leakage or gas. NO noise or microphonics.
This tube tested 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):
2,220(111%)
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 tubes 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.
