Scanned PDF of the September 2006 issue of AudioXpress, the audio electronics magazine, filed here under schematics. At almost 10 MB it likely holds full articles with construction projects, amplifier and loudspeaker designs, test results and circuit diagrams. The name gives no detail about which projects are inside, so browse the issue for the design you need. It serves as reference material for DIY builders and audio repairers rather than as a service manual for any specific device.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @pdf_servicemanual. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.