This site has down-loadable PDF files of many Pioneer/Lexus amps and head units:

user-service-manuals.com


The business arrangements are unusual but not expensive and I found them responsive to a PDF scanning quality problem I had. The file names are also rather confusing but after sending me the wrong file they quickly got me the right one.

One comment on the amp for my car, a GS400, is that the switching between CD and Tape/Radio is NOT done in the amp as some comments on this forum assumed, although signals from both terminate at the amp. The amp simply combines the two pairs of signals and relies on the unused source to go muted and hi-impedance when not selected. My amp also has an additional unpopulated input connector presumably for 3rd or 4th sources like TV in the Japanese market.