My apologies if this is a stupid question, or already answered many times -I am not sure what exactly to search for. I have a handheld recorder that came with two wired clip-on microphones, intended for interviews. They work perfectly with the recorder. However, when I plug these microphones into a mixer/amplifer (Behringer PMP5000) they don't work at all. I later purchased some more cheap clip-on mics, and they too have the same problem - work fine in handheld, don't work in "real" audio. Other microphones work fine in both situations (and with the same gain settings on the handheld, I get similar volumes between these mics and the ones that don't work on the mixers), so it does not seem to be a question of output levels. What could be the "special feature" of these cheap microphones that cause them not to work with audio mixers ?