The best sounding 6SN7 I have tried in my Supratek Syrah preamp is the cheap Russian military black base OTK.They are a bit microphonic however.They do sound very dynamic and vibrant though.The worst I have tried is the Shugyang Treasure CV181-Z which sounds quite muffled and dull.The USA Sylvania 6SN7GT black base is decent but a bit lifeless.What would be nice is something with the dynamics and vibrancy of the Russian military and the quietness of the others.Any suggestions.
By the way the Supratek is a fantastic sounding preamp.I own a Supratek Cabernet 300B as well.