Recording straight to laptop

I've been using my laptop and Mbox now when recording from a sound board. I used to plug into my minidisc, but realized that I can get better sound by avoiding the minidisc's compression and going straight in to my computer.

Last week, I recorded Barbara Kingsolver's reading that promoted her new book, Animal, Vegetable, Miracle. Initially I had problems receiving signal and here's why:

I only needed to record in mono and used just a single quarter inch sound in. But I was plugging it into the TOP location (see the red "2"?). I could hear sound in my headphones, but didn't see signal in Protools.

Then I took the plug out and put it into the BOTTOM location (see the red "1") and I had signal.

Now I know: if I only have one plug, start from the bottom.