Making a Vacuum Tube Amplifier

A triode is the active component in a vacuum tube amplifier circuit.

A vacuum tube amplifier uses technology that has been around since the early 20th century: the triode. A vacuum tube triode may be a part of an amplifier that provides high-power (and low-distortion) audio amplification. One common vacuum-tube-based amplifier is the Class-A amplifier circuit. Vacuum tube Class-A amplifier circuits are commonly found in guitar amplifiers; however, this type of amplifier circuit may be used in any amplifier application where a high-fidelity output signal is required.

Things You'll Need

• 1 12V DC power supply
• 1 6V DC power supply
• 1 100 Microfarad electrolytic (polarized) capacitor
• 1 1500 ohm resistor
• 1 100 kiloohm resistor
• 1 6CG7 twin triode vacuum tube
• Electrical wire
• Electrical pliers
• Electronic solder
• Soldering iron
• Two solder-type ring terminals

Instructions

1. Cut six pieces of wire. Strip 1/2 inch of insulation from each wire end. Place a ring terminal over one end of the first piece of wire. Solder the wire to the terminal. Place the other ring terminal over one end of the second piece of wire. Solder the terminal to the wire.

2. 

   An electrolytic capacitor has a "-" marking over the negative lead.

   Twist the free end of the first wire to the negative lead on the capacitor. Solder the connection. Twist the positive capacitor lead to the triode grid lead (pin 2 on the 6CG7). Solder the connection.

3. Twist the free end of the second wire together with one end of the 100 kiloohm resistor. Solder the wire pair to the triode plate lead (pin 1).

4. Twist one end of the 1500 ohm resistor to the cathode lead (pin 3). Solder the resistor lead to the cathode lead. Twist one end of the third wire to the free 1500 ohm resistor lead. Solder the connection.

5. Twist together one end of the fourth wire with the free end of the 100 kiloohm resistor. Solder the connection.

6. Attach the free end of the fourth wire to the positive terminal on the 12V power supply. Attach the free end of the third wire to the negative terminal on the 12V power supply.

7. Twist the free end of the fifth wire to the first triode heater lead (pin 4). Solder the wire to the lead. Twist the free end of the sixth wire to the second triode heater lead (pin 5). Solder the wire to the lead.

8. Attach the free end of the fifth wire to the positive terminal on the 6V power supply. Attach the free end of the sixth wire to the negative terminal on the 6V power supply.

9. Connect the signal input wire to the ring terminal at the end of the first wire. Connect the output device to the ring terminal at the end of the second wire.

References

• Mesa Boogie: Class A Exposed and Explained
• "Electronic Devices"; Thomas Floyd; 1996
• DR Tube: General Electric 6CG7 Twin Triode