The JJ Valve KT66 is manufactured in Slovakia, in what was formerly the Tesla factory. Due to their high-quality build and dependable performance, the JJ tube range has significantly expanded, making the JJ KT66 valve now available for purchase. It's an excellent option for Hi-Fi enthusiasts and guitarists seeking that robust American sound with improved tight lows and increased headroom. When replacing a 6L6 with a KT66, minor bias adjustments or modifications may be required.