The user manual for the GNX4 states:
NOTE: DigiTech recommends that you do not use the GNX4 as your default sound playback
device. This is configured in Windows in the Control Panel under the Sounds and Audio
Devices Properties. Windows Audio Samples are generally recorded at full scale level and if
played back through the GNX4 may be very loud in comparison with the configuration of audio
level in the GNX4 What are your PC? specs and what hardware do you have connected to it?