Connect the Babyface Pro to your computer via USB and make sure it is recognized by your operating system and the RME TotalMix software.

Connect a cable from the right output of the Babyface Pro to the input 1 or 2 at the back. This will create a loopback connection that will allow REW to measure the latency and frequency response of the sound card.

Download and install the latest beta version of REW.

Launch REW and go to Preferences > Soundcard. Select ASIO as the driver type and ASIO4ALL v2 as the ASIO device. Click on the ASIO Control Panel button and make sure the Babyface Pro inputs and outputs are enabled and have the same sample rate.

In the REW Preferences > Soundcard, set the output device to the right output channel of the Babyface Pro and the input device to the input channel that you connected the loopback cable to. You can use the Test buttons to verify the signal path.

Click on the Soundcard Calibration button and follow the instructions to measure the loopback timing and level. You will need to adjust the output and input levels of the Babyface Pro using the RME TotalMix software or the hardware knobs to avoid clipping or distortion.

Once the sound card calibration is done, you will need to calibrate your microphone. If you are using a USB microphone, such as the UMIK-1, you will need to download the calibration file from the manufacturer's website and load it in REW. You will also need to enter the sensitivity parameter of the microphone in REW Preferences >Mic/Meter.

If you are using a non-USB microphone, you will need to connect it to the other input channel of the Babyface Pro and use a sound pressure level (SPL) meter to calibrate the microphone level in REW. You can use the built-in SPL meter of REW or a separate device, such as the Radio Shack SPL meter.

Yes, this button activates the internal loopback function. The signal on the selected hardware output is directly looped to the corresponding input within TotalMix, so to say a 'virtual' connection on digital stage.