Demagnetizers, also known as degaussers, are used to demagnetize magnetic tapes, erasing unwanted programs. They can also be applied to demagnetize other parts of tape recorders (such as heads, flywheels, take-up reels, head covers, etc.) and repair tools. A demagnetizer can be homemade: choose a 40-watt line transformer or a five-tube radio's power transformer with an E-shaped iron core, removing the I-shaped cross-sectioned laminations. Wind approximately 1000 turns of 0.55 to 0.7mm enameled wire, with each layer separated by 0.1mm kraft paper. Connect the two ends of the coil to a 220V power source. The demagnetizer can be placed inside a wooden box, with a spring-button switch mounted on top. The opening of the iron core serves as the demagnetization surface, and the wood thickness of the demagnetization surface should not exceed 3mm.

When degaussing a tape, first plug in the degausser, hold the degausser and press the button to turn it on. Bring the degausser close to the tape reel on the desk and slowly move it in a spiral from the edge to the center of the reel. Then, gradually pull the degausser away from the tape, stopping at least one meter away, and release the power button to complete the degaussing. To degauss the tape head or other recording device tools, simply move the degausser's degaussing face over them from left to right or right to left slowly. When degaussing these objects, keep the tape to be saved away, otherwise, it may also be degaussed.

Demagnetizing tape or tape heads should not be abruptly disconnected from the demagnetizer's power source, otherwise, due to the magnetic field not fading gradually, residual magnetism may remain, which can increase noise during recording and playback.

The placement of the degausser should be kept away from magnetic objects such as speakers, dynamic microphones, and meters to prevent weakening or loss of magnetism, which may damage them. Continuous use of the degausser should not exceed a few minutes, as prolonged use can easily burn out the coil.