Generally mics with 1/4 plug are high impedance and mics with XLR connectors are low impedance. Be aware that there are any number of exceptions.
For you as a harp player it isn't a matter of one impedance rating being better than the other. The important thing is to match the impedance of your mic to whatever you are plugging it in to. A mis-match of impedance will rob you of power and prevent the mics characteristics from shining through. The greater the difference the worse the problem. Now, you don't have to match exactly although the closer the better.
Here's the deal; a mic rated in the 150-600 ohm range is considered low impedance. Plug these into a PA and you're good. A high impedance mic (in the 10000 ohms range) can go directly into an amp or effects pedal because they also have higher input impedances. If you wish to use components with different impedances you need to buy an impedance matching transformer and insert it between them in the signal chain.
I'm far from experienced in this. My second mic, an e-bay purchased RE-10 arrived last night. I used an adaptor without a transformer, plugged into my amp and, besides hum, got nothing at all . I'll have to go shopping tonight. Recommendations for an inexpensive transformer anyone?
Paul
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