This product features a 6J1 vacuum tube used in conjunction with an LM1875 amplifier circuit, incorporating amplification functionality. The 6J1 tube acts as a buffer to reduce digital harshness and transistor-based sound characteristics, delivering a more natural, smooth, and refined audio experience. It offers improved sound quality compared to standard LM3886 or TDA7294 amplifiers. The design is based on the 6J1 tube buffer circuit principle inspired by analog audio equipment, optimized for enhanced stability and performance. Tube performance is improved by approximately 10% over original reference designs. The board supports dual AC 18V input, eliminating the need for high-voltage power supplies. Built-in voltage boosting allows users to enjoy the benefits of high-voltage tube operation even with lower input voltage. Power operation: Upon power-up, the tube filaments begin heating, followed by gradual voltage boosting. Once the filaments are sufficiently heated, the boost process completes, ensuring safe and stable operation. The power supply uses four 470F capacitors for clean filtering, preventing AC hum. The filament is powered by DC 12V, with two tubes connected in series. DC filament supply helps minimize noise. The output automatically switches between headphone and amplifier outputs. When a headphone is inserted, the amplifier output is disabled. When no headphone is connected, the signal routes to the amplifier output. Headphone output level is slightly lower than direct digital output, with moderate driving capability. If this configuration is acceptable, the headphone output can be used effectively. After processing through this unit, headphone sound becomes more detailed and refined. The headphone output can also serve as a preamp output to drive a secondary amplifier stage. Color: Not specified Material: Metal LM1875T Amplifier: Based on classic European LM1875T design Wiring: Well laid out and reasonable Performance: Outstanding Popular among DIY audio enthusiasts The design retains all original alignment points and core performance characteristics while upgrading key components. The addition of the 6J1 tube enhances overall sound quality and clarity. Power Supply Voltage: Dual AC 18V, 3A, 60W or higher (maximum input must not exceed dual AC 19V, nor fall below 18V, to avoid improper tube operation or distortion). For use with AC 12V input, a 2.2 wire-wound resistor is required, which results in slightly reduced amplifier output power. Amplifier / Preamp Output: Gain approximately 0.8. The amplifier function can be utilized with high-sensitivity headphones. Output can also be used as a line-level signal to drive another amplifier, adding tube warmth. LM1875T Amplifier Output Power: Typical 20W (up to 30W maximum) Speaker Impedance: 48 ohms Harmonic Distortion: Less than 0.04% Signal-to-Noise Ratio: 105dB Frequency Response: 14Hz100kHz (RC filter design allows theoretical range of 3.29Hz482.29kHz) Package Contents: 1 x LM1875T amplifier board kit Note: Only the items listed are included. Other accessories are not part of the package. Note: Lighting and display settings may cause slight color variations in the product image. Measurement tolerance is +/- 13cm.