20W Power Tube Amplifier with EL34

The following diagram is the circuit diagram of 20W power amplifier which build based tube component EL34. EL34 is very famous tube and great for power tube amplifier.

20W tube amplifier

The circuit above is complete circuit contains tube amplifier circuit diagram and power supply circuit diagram. To make the stereo channel amplifier, build the similar amplifier circuit only and connect to the power supply using parallel connection with another same amplifier.

The tube EL34 is a thermionic valve or vacuum tube of the power pentode type. It has an international octal base (indicated by the ‘3’ in the part number) and is found mainly in the final output stages of audio amplification circuits and was designed to be suitable as a series regulator by virtue of its high permissible voltage between heater and cathode and other parameters. The American RETMA tube designation number for this tube is 6CA7. The Russian analog is 6P27S (Cyrillic: 6?27C).

The tube EL34 was widely used in higher-powered audio amplifiers of the 1960s and 1970s, such as the very popular Dynaco Stereo 70 and the Leak TL25(mono) and Stereo 60, and is also widely used in high-end guitar amplifiers because it is characterized by greater distortion (considered desirable in this application) at lower power than other octal tubes[citation needed] such as 6L6, KT88 or 6550.

20W power tube/valve amplifier circuit diagram with EL34

4 thoughts on “20W Power Tube Amplifier with EL34

  1. Alexsander Bittencourt Vieira

    Only Bias circuit is incorrect. EL34 operate with negative voltage in the grid 5. For correction, invert diode and capacitors polarity in power source: 10uF 100V with positive connector in ground 🙂

    Adjust bias corrent 35-45mA range. Caution for plate not stay red.
    Good look and sorry… my english is less.kkk

  2. karnakstudio

    The schematic diagram is incorrect, in the grid of El34 the bias voltage is negative….the bias circuit is incorrect

  3. circuit diagram Post author

    12AX in a tube. It has pin which need to be connected to power source. Find the datasheet to know its pin assignment.
    1M in a value for resistor. For diode, you may use GBPC102 bridge diode rectifier or 4x1N5400 , 4x1N5401 or 4x1N5402 single diode rectifier

  4. Christotech

    Pls i want to know wt kind of compnt is this 12AX,1m,5.34 & the number of the bridge retifier.The output,input of the power pack.I wil be glad 4 ur reply

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