807 (vacuum tube)

807 is the designation for a high-power, high-mu triode vacuum tube. Developed during the early days of electronic amplification, the 807 found extensive use in a variety of applications, primarily in audio power amplification and radio frequency (RF) power amplifiers. Its relatively high power output capability, combined with good gain, made it a popular choice for both amateur radio enthusiasts and commercial equipment manufacturers.

Technical Specifications

While precise specifications vary slightly depending on the manufacturer and specific tube version, common characteristics include:

• Type: High-mu triode
• Maximum Plate Dissipation: Generally in the range of 25 to 30 watts.
• Maximum Plate Voltage: Typically several hundred volts.
• Maximum Grid Voltage: A negative voltage, dependent on the operating point.
• Amplification Factor (μ): Significantly higher than many smaller tubes, providing substantial voltage gain.
• Transconductance (gm): A measure of the tube's current amplification capabilities.
• Operating Frequency: Capable of operation across a range of frequencies, though limitations emerge at very high frequencies.
• Filament Voltage and Current: Specific values vary depending on the tube version; commonly operated at low voltages.

Applications

The 807's robust design and power handling capabilities led to its use in several key applications:

• Audio Amplifiers: Used in high-fidelity audio amplifiers, often in push-pull configurations to achieve higher power output and better linearity.
• Radio Frequency Amplifiers: Its high gain and power handling made it suitable for radio transmitters and receivers, particularly in amateur radio equipment.
• Industrial Control Systems: Found application in certain industrial applications requiring power amplification.

Construction and Operation

Like other vacuum tubes, the 807 comprises a cathode (electron emitter), a control grid (controlling electron flow), a plate (anode, collecting electrons), and supporting elements sealed within a glass envelope under vacuum. The application of appropriate voltages to these electrodes controls the flow of electrons, generating the desired amplification.

Alternatives and Successors

The 807 was eventually superseded by more modern solid-state devices like transistors and integrated circuits, which offer higher efficiency, smaller size, and increased reliability. However, the 807 remains of interest to vacuum tube enthusiasts and collectors due to its historical significance and unique sonic characteristics in audio applications. Several other tubes, with similar power handling and characteristics, were also available during the 807's era.