Flat recordings. No bass. Tiny sound

Hi, I’m using Audacity 2.3.3 on my Macbook Pro running Sierra. I used an earlier version of Audacity on years ago on a much earlier mac operating system with no problems when i digitised my LPs. Now with the latest Audacity and Sierra I’m getting flat lifeless recordings from my NAD Tape Deck. I’ve connected the deck via an amplifier to my Mac the same ways as before. Any suggestions of what could be the problem.

Now with the latest Audacity and Sierra

Depending on how new the machine is, it may not have a stereo line-in any more like the older ones did. Do you have one of these? The headphone is Stereo Line Out and the circle with black arrows is Stereo Line-In.

Koz

Thanks for your reply Koz. Yes my current Macbook doesn’t have a line in. From memory my previous one didn’t either but them my memory isn’t what it used to be.
Is there another way around this through the USB ports?