The Sphere microphone has a “Cal” (calibration) switch on it. What does that do?

When calibration mode is switched on the front capsule output is fed to both XLR outputs, so there are identical signals on both channels. This makes it easy to use the metering in your DAW or in the plug-in to verify and set the gains of preamp channels, if using a non-calibrated mic preamp.

For more info see our FAQ: What is the calibration process for analog mic preamps with continuous gain adjustment?