Please follow these detailed instructions for recording a vocal track onto a mono audio track in Cubase LE4/LE5/LE6 (not sure which version of Cubase you are using)
First, please go to Tascam’s website and download and install the latest ASIO driver for your US-800 device and make sure Tascam’s driver is supported on Mac OS 10.7 Lion.
After installing the latest driver, please open Cubase LE4/LE5/LE6.
Inside Cubase go to Devices, Device Setup, VST Audio System, and make sure the driver for your Tascam US-800 is selected and click OK.
Next go to Devices, VST Connections, Inputs, and under Bus Name at the bottom right-click on Stereo IN and select Remove Bus.
Now at the top click on Add Bus and Add 1 MONO BUS.
Next go to Project, Add Track, Audio, and Add 1 MONO audio track since you are recording a mono signal from your microphone.
Next on your new MONO audio track, make sure the audio input on the track is set to the MONO IN 1 on your Tascam US-800 device and that the Stereo OUT is set to STEREO OUT.
Next click on the little speaker icon and highlight it next to the red record button on the audio track.
You should now be able to see blue metering on the track when you talk into your microphone.
Now press record on the transport bar and should be able to record your microphone onto the MONO audio track.
After you have recorded your vocal, press Stop on the transport bar, and then click on the little speaker icon next to the red record button on the audio track so that the speaker icon is NOT highlighted.
You should now be able to playback and hear your recording. Your studio monitors need to be connected to the Stereo Outputs of your Tascam US-800 device in order to hear the playback.