Abstract: The invention provides a set top box with karaoke functions. The invention consists of a video and audio real-time casting function processor, an audio/video decoding processor with high definition multimedia interface technology and an audio remix processor. Therefore, the multimedia image can be projected onto a large screen and the output audio and the microphone sound can be mixed together and then output to the audio equipment, so as to achieve a better karaoke singing result.

Abstract: A signal filter includes a main circuit board having two opposite sides each having a longitudinal grounding circuit formed on the main circuit board and two opposite ends each having a connector attached to the main circuit board. The connector has a metal portion electrically connecting to the grounding circuit of the main circuit board to promote the grounding effect of the signal filter. A tube is mounted around the two connectors to form a chamber to hold the main circuit board in the tube and prevent water vapor from permeating into the signal filter and damaging electric components in the signal filter.