I have a Grace TAPE2USB ll and I cannot get the internal microphone to turn off while recording with Audacity. I’ve turned the microphone off on the Grace unit but it seems to make no difference. What can I do?
Are you sure you are not recording the mic built-into your laptop? Make sure you’ve selected the Grace unit as your recording source, and unplug the USB to make sure the microphone sound is actually getting into the computer from the Grace…
What can I do?
Open it up, and cut the wires to the mic or unsolder the mic? 
(Odds are the mic is soldered directly to the circuit board, and there are no wires you can cut.)
Or, just get a different cassette deck! Make sure to get one with line-out (one that’s designed to hook-up to a home stereo), and you’ll need some adapter cables to connect to line-in on your soundcard.
And if you have a laptop (with no line-in), you’ll need to get something like the Behringer UAC202 USB audio interface. Note that most regular “USB soundcards” are like laptops with only mic-in and headphone-out, so don’t bother buying one.
Thanks DVDdoug. With your advice I was able to solve my problem. I am new at this and it shows!