I am using a MacBook Pro with 10.9.4 and Audacity 2.0.5.
How do I either disconnect the computer’s built in microphone or have it recognize the Audacity usb as a 2nd input? It will record information from the turntable but also any sounds picked up by the microphone.
Audacity only “sees” external devices that are already present when you launch it.
If you connected the USB turntable after launching Audacity, use Transport > Rescan Audio Devices in the Audacity menu bar to alllow Audacity to discover the turntable.
Then open Device Toolbar and choose the computer speakers for output device and the USB Audio CODEC for input device.
I also suggest you have a look at Recording with USB turntables or USB cassette decks - Audacity Manual .
Gale
Thanks, I quit Audacity, plugged in the USB from the turntable and the computer recognized the 2nd input. Problem solved.