Supports replaceable tubes including 6J1, 6J2, 6J3, 6J4, 6J5, 6A2, 6K4, 6K5, 6AK5, 6AU6, 6BA6, 6BD6, EF93, 6K7, GE5654, and other equivalents. Power supply: DC 12 16V, current at least 1A. For performance, a DC 12V 1.5A supply is recommended. Power socket: DC 3.5/5.5 x 21 mm. Tube: 6J3 (the tube is disassembled). Function and compatibility: Provides a tube socket platform that accepts a wide range of common tubes, enabling replacement and experimentation with different tube characteristics. Use scenarios: 1) Audio hobbyist or DIY project: swap tubes (among listed types) to explore tonal changes and find a preferred sound signature. 2) Refurbishing or upgrading vintage gear: use the supported tubes to worn components and tailor performance to modern listening preferences. 3) Educational or testing bench: experiment with different tube types to understand how tube selection affects circuit behavior and output.