SID2SID & Stereo SID Project – Vintage is The New Old
The SIDFX Sound Mod – breadbox64.com
Stereo SID with VICE C64 emulator | ezContents blog
Part 1: SID2SID & Stereo SID - Commodore 64 Mod - YouTube
Internal Stereo SID board for the C64 and C128 | nIGHTFALL Blog / RetroComputerMania.com
Mingos Commodorepage
GitHub - tebl/C64-Stereo-SID: There are many Stereo SID boards, but this one in mine... Add a second SID of the same type or newer substitutes for adding stereo audio to your system...