![Audion amplifier. Diagram of an Audion triode valve that was the first amplifier. It was invented by Lee De Forest in 1907. De Forest worked on vacuum Stock Photo - Alamy Audion amplifier. Diagram of an Audion triode valve that was the first amplifier. It was invented by Lee De Forest in 1907. De Forest worked on vacuum Stock Photo - Alamy](https://c8.alamy.com/comp/2ADNH7B/audion-amplifier-diagram-of-an-audion-triode-valve-that-was-the-first-amplifier-it-was-invented-by-lee-de-forest-in-1907-de-forest-worked-on-vacuum-2ADNH7B.jpg)
Audion amplifier. Diagram of an Audion triode valve that was the first amplifier. It was invented by Lee De Forest in 1907. De Forest worked on vacuum Stock Photo - Alamy
Karltone - The Triode Valve - The diode valve is essentially a rectifier, turning AC into DC, whether these be large mains voltages or relatively small signal voltages, as in the detection
![Vintage Admiral 5BK7A High Frequency Twin Triode Valve- BangyBang Tubes : Amazon.ca: Musical Instruments, Stage & Studio Vintage Admiral 5BK7A High Frequency Twin Triode Valve- BangyBang Tubes : Amazon.ca: Musical Instruments, Stage & Studio](https://m.media-amazon.com/images/I/61d3Fj4KWTL.jpg)