A shame that many of these sites are taken down. On Gearslutz there is a thread about where to find schematics:
https://www.gearslutz.com/board/geekslutz-forum/481428-free-audio-schematics-download-3.html
And on www.audioschematics.dk is a list of sites: https://audioschematics.dk/more-schematics/
https://www.gearslutz.com/board/geekslutz-forum/481428-free-audio-schematics-download-3.html
And on www.audioschematics.dk is a list of sites: https://audioschematics.dk/more-schematics/