About feedback: I found an interesting device, that works great for me. When I perform in tiny places (normally small bars) feedback is (almost) inevitable. This feedback destroyer, called Behringer Shark, has several extremely narrow filters that dramatically reduce the gain of specific frequencies. There are 12 filters in total. It also has a "learning function" that searches the frequencies where the feedback occurs, and ajusts the narrow filter gain reductions accordingly. The great things are: i) ease of use with the learning function ii) the voice quality is not too much affected because the filters are so narrow. It incorporates phantom power, for those who prefer condenser mics. It's a really small and light piece of equipment, that turns out to be really useful.

José Matias.