A vacuum tube is somewhat like a light bulb: constructed of glass and inside this glass envelope there is a heated filament. The interior of the tube has all the air evacuated (thus the vacuum). The heated filament gives off light, which we can see, just like a light bulb.

However, the light in the tube is just a byproduct and the light just looks good. Of more importance are the electrons which hover around the heated filament. Vacuum tubes contain other elements which are the real reason for their function. In a basic tube, there is the filament (often called the “cathode”), and a metal strip (called the “anode” or “plate”) situated near the inside edge of the tube.

When a positive voltage (usually in the hundreds of volts) is connected to the plate, the electrons at the cathode, by their negative charge, are attracted to the positive charge of the plate.

Flow of electrons from one point to another is called "current" (measured in amperes, or "amps"), and movement of electrons from the cathode to the anode falls into this category.

THX is the trade name of a high-fidelity sound reproduction system for theatrical movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. THX was developed by Tomlinson Holman at George Lucas's company Lucasfilm in 1983 to ensure that the soundtrack for the third Star Wars film, Return of the Jedi, would be accurately reproduced in the best venues.

Each THX Certified Product is engineered to perform best in specific room environments. Room size, acoustic design and system setup are all critical factors to how movies, music and games are experienced in the home.

THX Ultra2 Certified Products are engineered and designed for large home theaters. Viewing distance of approximately 12 feet / 4 meters from the display to the listening position.

Digital Theater Systems, a company which produces multichannel audio systems for cinema and home video, refers to an 6-channel audio system.

A 6-channel surround sound system developed by Dolby Laboratories. The audio is separated into front left, center, front right, rear left, rear right, and low frequency effects.