The real trick was biasing the deck for a specific tape type. Different tapes required somewhat different biases. These had to be set using an oscilloscope for almost all decks. I liked TDK SA better than Maxell UDXL II; it sounded more lively. But as Johnd said, they were a bit spotty on construction. The best sounding cassette tape I ever heard was Sony UCX-S. I still have my Tandberg TCD 440A biased for it as the chromium oxide selection and it sounds terrific. They were well enough constructed that I have tapes I made in the mid 80's that can't be distinguished from the original vinyl. They also outperformed the TDK MA-R tapes, especially for the cost difference.
