Recording Problems - Sound level drops

I am using Snow Leopard on my Mac. Whenever I record a vinyl record to Audacity (running a turntable to a USB phono preamp with volume control) the sound level in Audacity drops (in the waveform). I adjust the volume for the recording so it won’t clip, but after I stop the recording, the sound level drops. Is there something to prevent this or is there something wrong with my laptop ?

Any info is appreciated

Is this issue resolved: https://forum.audacityteam.org/t/can-a-usb-audio-codec-be-installed-on-a-mac/48840/1
If so, please post to that topic to confirm.