Class A Single end 2SK1058 Amplifier

Sure there has to be single active component in an amp in order to get the gain to be called an AMPLIFIER. That's a simple amplifier as a single end tube amplifier. A single end vacuum tube Amp need a resistor or two and an output transformer. So I design a FET amp around the same simplicity of design. One audio grade MOSFET, a couple of resistors and capacitors and a heavy duty well filtered power supply. The schematic for the amplifier section is shown in Figure 1.

The amplifier is built around the Hitachi 2SK1058 N-Channel MOSFET. A schematic and pin diagram for the 2SK1058 is shown in Figure 2. I used Sprague capacitors for the input coupling and a large electrolytic on the output with a 10µF polyester bypass capacitor. The four 10W non-inductive wire wound resistors act as the load. The four resistors are 15ohm and 10W each which I wired two in series for 30 ohms and then the two sets of 30 ohms are wired in parallel to give a total resistance of 15 ohms. These get extremely hot and burn about 30W at idle. Yes, Class-A amplification is very inefficient. I burn over 20 Watts to get only about 4.8 audio Watts per channel! The heatsink I used is rated at 0.784 °C/W.

2SK1058 Pin Out

Schematic 2SK1058 Amplifier

Power Supply of  2SK1058 Amplifier

Stereo 2SK1058 Amplifier Module