Now, there are three possibilities…
* If the noise levels are about the same. In this case you can stop worrying and get back to recording.
* Recording #2 is noisier than Recording #1. This is normal. As above, stop worrying.
* Recording #1 is noisier than Recording #2. This is a distinct warning sign that something is wrong with your preamp. This simply should not happen. Perhaps it may be time to look into a better quality pre amp or the unit you have may need repair or calibration.