Bile tube FD422 to make 2×12W class A single-ended power amplifier circuit

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

MOS power IC full range

1.5PF SOT23-6 Low Capacitance 5V Breakdown Voltage 6V SRV05

Photocoupler

The author chose FD422 tube (direct heating type of FU7 tube) to make a class A single-ended power amplifier, with a speaker with a sensitivity of 91dB, the sound is extraordinary.

The mono circuit is shown in the figure, and the other channel is the same. The front stage uses 6J1 tube, the power amplifier tube uses Dawning FD422, the similar tube has Nanjing FD422, FU25, and the inlet tube has 2E22, 2P22 and so on. The FD422 parameter is the filament 6.3?0. 9A, the maximum anode voltage is 750V (screen current 55mA), the screen consumption is 40W, and the maximum class A output power is estimated to be 40W × 1/3 according to the screen consumption, which is about 13.3W. The output transformer is selected from Changsha Meile Electronics Factory, the model is 3. 5k/30A, and the frequency response is 20Hz~54kHz. The power transformer has a capacity greater than 180VA and a shield is added. Electrolytic use of domestic old-fashioned aluminum shell Tianhe brand, coupling capacitor with oil-immersed capacitor. After the welder has been adjusted, it will be successful several times.