Occasionally, when I'm using ardour the mic starts to crackle, it's not a wire or mic problem I'm pretty sure. I think it's jack because when I record in audacity without using jack, there is no crackle. Then I use jack with audacity and it crackles. In ardour if I change jack's latency either way, up or down, the crackling stops for about a minute, then starts again. To be a little more specific about the crackle, it's kind of an echo too, I say something first it comes out crackly then it comes out normal. I'm on leopard if that makes a difference too.