Every model of PS1 is capable of matrixed multi-channel surround sound. This is achieved by piggybacking an inverted-phase signal across both left and right audio channels. Under normal stereo configuration circumstances, this results in standard stereo audio. But if the signal is sent to a device (such as a home theater receiver or dedicated outboard surround decoder) capable of decoding matrixed surround, a true multi-channel surround sound experience is achieved. There are the standard stereo left and right signals, but compatible games (Chrono Cross, Final Fantasy VIII, CoolBoarders 4, etc.) will be sending a limited-bandwidth inverted-phase signal across each of the two stereo RCA cables, that are decoded by the appropriate device into a Center and a Rear channel as well! This is how Dolby Surround works, and it's the same as the way it works on VHS and some LaserDiscs as well as some early DVDs and other 1990s game consoles. Some games paid for a Dolby license and had the Dolby Surround logo printed on the box or even the cartridge label, they were designed specifically to be decoded by Dolby Pro-Logic, which was the codec (for lack of a better word) for decoding Dolby Surround. Other games didn't pay for a Dolby license but still offered a Surround option in the audio options in-game that was decoded the same way. Still other games simply had "Mono" or "Stereo" options in the in-game menu, but the "Stereo" option was also passing along a matrixed surround signal and could be decoded appropriately. Resident Evil 2 is one such game. Some modern AV Receivers are quietly dropping compatibility with older surround formats, but others are holding strong. It is recommended to research the surround format capabilities of a given receiver before purchasing new.