Abstract: An adapter is disclosed that converts a received stereo audio signal into a signal having more than two channels, such as a surround sound signal. For example, the adapter may convert a stereo signal to a 5.1 signal. Other types of surround sound may alternatively be generated from the stereo signal. In addition, the adapter may have no active electronic components. That is, the adapter may require no power source to perform the signal conversion other than the power inherent to the stereo signal itself. Where the adapter requires no source of power and uses relatively few parts, the adapter may be assembled in a relatively small housing.