As far as I know, none, except that most high-z inputs are 1/4" TS (tip-sleeve) receptacles, and are generally unbalanced. In other words, a high impedence mic is plugged into an instrument jack, and will work when plugged into a guitar amp, etc. It's not the cable that's high-z or low-z, it's the mic's output and the thing it's plugged into. All mics used to be high-z, and some old PA's have only high-z inputs. Characteristically, low-z mics use XLR connectors, and tend to be quieter.-Richie