Cassette to audacity background humming

Oh please help - have spent weeks on this.
I have Mac OS X 10.6.8
Audacity 2.0.5
I have a small - new, but old-style tape recorder, like business men used years ago. Aux cord is going from the headset EAR (so that I don’t have to listen to it while it is taping) into the headphone jack (only jack) on a macbook pro.
These are old speaker tapes - I am not worried about quality. However, now matter which settings I use, and no matter which effects I add -
There is a constant, flat-line, hum in the background. Listening out-loud (i.e. on the computer) it is not that bad, but if I listen with headphones, it is very bad. The guy on the tape talks, and this flat-line hum is driving me nuts.

Any suggestions? I need exact directions, I’m new to this. I have tried many setting with volume — i.e. to move the microphone in Audacity to the highest setting and the volume on the cassette lower — but nothing has changed. At one point, I thought removing the bass worked, but the second time I recorded it all again – it was back.
Thank you – please help !! Thank you !!!

headphone jack (only jack) on a macbook pro.

Which MacBook Pro? 13"? Do you have provision to “turn the jack around” into a stereo Line-In?

Apple (upper left) > System Preferences > Hardware > Sound.

Do you have a switching panel or other control? Post a screen grab of what you have. Shift-Command-4 will let you draw a fence around the portion of the screen you want to capture.

Do you have one of these:

If you have a newer Mac, then you have no connection for that and you will need a USB adapter similar to this one that I use for my Stereo mixer.

Let us know.


Sorry. Wrong graphic.