Simple question, but I have not done this before. I want to connect an older stereo cassette deck to my iMac. I connected the line out from the deck to the audio input jack on the iMac. With the tape playing, I can "see" the audio signal in Preferences > Sound > Input. It stops and starts when I pause and play the tape, so it would seem the signal is there ok. However I have no sound from the speakers. Audio from browsers, Audirvana etc. are fine from the speakers. Am I doing this right?