Aiwa made some incredible cassette decks at the same time those Naks were made, mainly the top of the line f990. I had one, but sold it...as I owned three Awia decks. I still have both the f770 and f660. You would be hard pressed to distinguish between the source material and the tape. Awesome machines. I generally use TDK and Maxell tape type 11. Some pre recorded tapes sound absolutely wonderful on these machines.
