Will a soundcard allow me to use an Equalizer for USB headset?

I have a set of USB Sennheiser headphones. I want to have the ability to adjust the high's on them.
Will having a sound card allow me to do this, or does it only affect something plugged into the card directly?

The lows and mids are perfect, but I need the highs to be a little better for my FPS so I can hear better. That is my ultimate goal.

USB headphones have their own DAC, directly written to by the drivers/OS to output sound. Any sound card in your PC will have no affect on it.

Have you checked the drivers for it to see if there are any adjustments that you can play around with? What about Windows audio panel?

You might try something like this: http://sourceforge.net/p/equalizerapo/wiki/Documentation/, but I do not know if that will work on external USB DACs.

The headphones have the 3.5mm inputs, but it goes into a Dolby Digital "3D Game" adapter...so if I plug it directly into the sound card, it will mean I'll lose the virtual 7.1...

I'll give the Equalizer APO a try thanks!