I have been using my 545 on and off for a few years. Mine rarely gives me feedback problems, and breaks up easily. It works great with all of my amps. I usually play through a '59 Ampgeg Jet with 1-10'' Jensen. It also has worked great with larger amps. I have never used it through a p.a., but I assume it would not be hot enough, b/c this mic is high impedence. david lipkind