Power socket: DC 3.5/5.5 mm plug, 21 mm length. Tube: 6J3 (the tube is disassembled). Product compatible with replaceable tubes: 6J1 6J2 6J3 6J4 6J5 6A2 6K4 6K5 6AK5 6AU6 6BA6 6BD6 EF93 6K7 GE5654 etc. Power supply: DC 1216 V, current 1 A or more (DC 12 V 1.5 A supply is recommended). Key benefits and features Flexible tube compatibility enables a range of sonic and signal options through readily available tubes. Replaceable tube design allows easy upgrades or substitutions without changing the unit. Uses a standard DC power supply with widely available voltage and current options. Compact and straightforward to install in a desktop or DIY enclosure. Tubebased design offers a simple, handson approach to experimentation and learning with common tubes. Use scenarios DIY audio projects: use as a small tubebased preamplifier or signal stage in a home audio setup, with tube choice affecting tone. Lab or workshop testing: serve as a test module to experiment with different tubes (6J family, EF93, GE5654, etc.) and compare performance. Educational demonstrations: a practical tool for teaching tube substitution, basic electronics, and circuit behavior in a classroom or maker space. Notes The included tube for this unit is 6J3 and is disassembled for user assembly. When selecting a power supply, ensure it provides DC output within 12 to 16 V and at least 1 A; 12 V 1.5 A is recommended for stable operation.