Did you discover this because it sounded bad, or did you simply notice it visually?
In either case, does it sound bad? Does this happen on every transient?

That one would have a notiable level of "click type" info.

Are any USB devices connected?

What was your clock/word data?

Looks like one of 2 things:
1. You could be hitting the mic with too much airpressure, (looks like it might be a kick drum signal), and the mic electronics are not happy.

OR

2. You have a bad MSB in your digitzer and the polarity is reversed. Can you record other signals with the same negative excusion? Do they also invert the peaks like that?

Steve (these are slightly educated wild assed guesses)

Ok, we made test yesterday with different mics. We used a Shure beta 52 and waves are now "normal". I think it might be problem with the superlux that is too sensitive. Or a default in conception.

David : It sounded bad, distorted. Even though We recorded at low level it was horrible. The Mic was out of the bass drum. It happened on every transcient.

Bill : No USB connected, Recorded in 44100 / 16bits. We have try different setting with no luck.

Steve : This is a kick, and the mic was 6 inch outside the bass drum. What is MSB ?? The only mic that was doing such things was the Superlux PRA-218A.

I think I'll do more tests with the mic, if their is a problem I'll send it back to Avlex/Superlux

Thank very much for your help.

Consider simply micing the kick with a 57 at 2 feet for a reference wave. Look at it..it will be light on the bottom but anitomically close.