There are three things to consider: settings, operation and connection.
Please check each in the following order:
1) Confirm the audio output destination setting
Open [Audio] in the rekordbox Preferences and check that the [audio] and [output channel] are selected correctly.
For details, refer to [Checking audio settings] in [Starting the system] in the Instruction Manual.
2) Check the volume level operation
- Play a track.
- Set the TRIM knob to the center (12 o’clock).
- Slide the channel fader to the top.
- Slide the crossfader to the center.
- Turn the MASTER LEVEL knob to 2 o'clock.
If you don’t hear any sound from the headphones at this point, check the following:
- Turn the HEADPHONES MIXING knob to the center.
- Turn the HEADPHONES LEVEL knob all the way to the left.
- Press the MASTER CUE button.
- Turn the HEADPHONES LEVEL knob slowly to the right.
3) Check the connection of speakers and headphones
For details, refer to [Connections] in [Operation] in the Instruction Manual.
Even if you’ve already connected them, disconnect and reconnect them to make sure they’re properly connected.
You can read the Instruction Manual [here].