First of all, you should understand that optical fiber, coaxial cable and HDMI all transmit digital audio signals, but HDMI also has video signals attached to it. If his speaker matches the power amplifier, it is best not to change the power amplifier, but to use the input port of the original power amplifier. If the input port does not have a digital signal transmission port such as fiber coaxial or HDMI, then the digital signal can only be converted into an analog signal by the connector. \x0d\ Second, you just said that you changed an optical fiber input power amplifier, so this power amplifier must have digital decoding functions such as DTS or Dolby (not all power amplifiers have digital decoding functions), and the power amplifier with digital decoding function can be directly plugged into the optical fiber coaxial or HDMI cable for transmitting digital signals. Otherwise, the digital-to-analog converter can only be inserted before the input power amplifier. \x0d\ Thirdly, if all the above are normal, then there are only two possible problems: \x0d\ 1 The power amplifier input by your digital optical fiber does not match his 5. 1 speaker, so it is impossible to transmit the converted sound signal to all channel speakers; \x0d\2 You didn't switch the audio output to the optical fiber on the TV set-top box, but the default HDMI output audio, so the sound signal will only come out through the TV.