6SN7

The 6SN7 is a medium-mu (mu ~20) octal dual triode that many consider the finest-sounding small-signal tube ever made. Its separate cathode structure and generous physical size give it better linearity and lower distortion than the miniature 12AU7, which was designed as its noval replacement. The 6SN7 excels as a line stage, driver, and phase inverter, with a natural, open, dimensional sound quality that has made it the centerpiece of many reference preamp designs. Sylvania VT-231 (WWII era), Ken-Rad VT-231, and Tung-Sol round-plate variants are legendary among audiophiles, though Shuguang and Psvane produce credible current alternatives.