The most simple sound field effect power amplifier board circuit diagram

MOSFET imported original FET

The Hitachi MOS field effect amplifier tube is beautiful and fascinating, and many top-class telescopes are used in large quantities. The author selects the common easy-to-purchase and cheap board Hitachi 2SK399, 2SJ113 high-power tube welding system, the simplest power amplifier, the circuit is simple, only 23 components. Careful selection and commissioning, the sound quality is impressive. Good value for money, it is recommended.

As shown in the figure, Q1 ~ Q3 select 2N5401, 2N5551 (TV video amplifier tube) for differential and main voltage amplification, taking good frequency characteristics, good linearity and high withstand voltage. Q4～Q5 select the above-mentioned Hitachi 靓 对 pair 2SK399, 2SJ113 (100V10A100W), the linearity is good, and the effect is good. The above enlarged tube can also be used with a special audio tube for sound, and the sound quality can be further improved.

Production requirements: the differential tube and the power tube should be paired to improve the open loop linearity, improve the sound quality, and stabilize the midpoint zero potential. When Q1~Q2 is 05mA, the difference of HFE is ≤5%, and HFE is higher. When Q4~Q5 are between 01 and 3A, the HFE is as close as possible, which is basically the same. The resistor is made of a metal film resistor. Make it according to Figure 1. Adjust W1 so that the output midpoint is zero. This circuit can also increase the output power by incorporating an output tube or increasing the supply voltage. The measured power output is 50W when ±36V8Ω. The author used the Philips CDR-870 as the sound source during the audition. The Swans M1 was used as the monitor speaker, which showed pure sound quality, wide sound field, strong and powerful bass, and high-pitched sweetness with the charm of the tube amp, giving people a favorite sound. It is a Hi-Fi amplifier that can be worn and listened to.