The **211-R** is a specific electronic component most commonly identified as a **Radio Frequency (RF) Power Triode** vacuum tube. It is a variant of the legendary "211" tube, frequently utilized in high-end audio amplifiers and radio transmission equipment. --- ## 1. Component Overview The 211-R is a large, glass-envelope power triode. The "R" suffix often denotes a reinforced or ruggedized version designed for improved reliability in industrial or military applications. | Feature | Specification (Typical) | | :--- | :--- | | **Component Type** | Directly Heated Triode (DHT) | | **Filament Voltage** | 10.0 V (AC or DC) | | **Filament Current** | 3.25 A | | **Max Plate Voltage** | 1,000V - 1,250V | | **Max Plate Dissipation** | 75 Watts - 100 Watts | | **Base Type** | Jumbo 4-Pin (Bayonet) | --- ## 2. Key Electronic Parts & Construction The internal structure of a 211-R consists of three primary active elements housed in a vacuum: ### A. The Filament (Cathode) * **Material:** Thoriated-Tungsten. * **Function:** When 10V is applied, it glows brightly (like a lightbulb) and emits electrons via thermionic emission. * **Characteristic:** The "Directly Heated" nature provides a very clean signal path, which is highly prized by audiophiles. ### B. The Grid * **Material:** Molybdenum or Graphite. * **Function:** This acts as the "gatekeeper." Small voltage changes on the grid control the large flow of electrons from the filament to the plate, resulting in **amplification**. ### C. The Plate (Anode) * **Material:** Often Graphite or Metal (molybdenum) with a blackened coating. * **Function:** Collects the electrons. In the 211-R, the plate must be robust to dissipate the high heat generated during high-voltage operation. --- ## 3. Applications The 211-R is used in two primary fields: 1. **High-End Audio (Hi-Fi):** Used in "Single-Ended Triode" (SET) amplifiers. It is famous for producing a "warm," holographic sound with significant power (approx. 12–20 watts per tube in Class A). 2. **RF Transmission:** Originally designed for radio transmitters, it can handle high frequencies for AM broadcasting and induction heating. --- ## 4. Safety and Operation Notes * **High Voltage:** Operation involves voltages exceeding 1,000V DC. This is **lethal** and requires specialized power supply components (transformers and capacitors). * **Heat:** The tube runs extremely hot. Adequate ventilation and ceramic sockets are mandatory. * **Orientation:** Most 211-R tubes should be mounted vertically to prevent the internal filament from sagging and shorting against the grid.