where to find owners manuals

Check out audiocircuit .com The owners manuals for the amp and preamp are available. You need to register to download the manuals. There is a wealth of info on the site and it is continually being updated. Hope this helps.

Here's a copy of the CA-5,

http://akdatabase.org/AKview/albums/userpics/10007/Nakamichi%20CA-5%20User%20Manual.pdf

and both available here as Radman707 has stated,

http://www.hifi-manuals.com/Nakamichi

No guarantee, but try HiFiEngine.com