dj control instinct virtual dj 7.4 headphones not working

hey guys, 

i just bought a hercules dj control instinct and i installed virtual dj 7.41. this version should be natively supported by the dj control instinct and everything is working fine, except the headphones. i turn the headphone volume up but the headphones dont work. in the settings, channel 3/4 are fully turned up and channel 3/4 default are checked as the headphone output.
in djuced the headphones are working.

thanks.