Anyone have any suggestions as to how to get cassette players to the right volume for computers, aside from trial and error?   Can a multimeter be used to streamline the process?   This applies to using cassettes on systems like the TRS-80, Apple II, or Timex Sinclair 1000, etc, that don't have proprietary units like Commodore or Atari 8-bit that tend to be easier when working.   I know I can use trial and error, but it's usually torture to get the volume right. As well, I'm never sure if