If you have both an XLR input and a 1/4" LINE IN on your mixer, you can connect to a channel LINE IN jack if you are close enough to the mixer to do so.The XLR input is better for signals that have to travel over a greater distance, or environments where interference, hum, or noise is an issue. Some keyboards have XLR outputs. If your keyboard is not equipped with XLR output jacks, you can use a direct box ("DI box") equipped with an XLR output connector to convert the signal into a lower-impedance, balanced signal.