Can i record from USB while listening via jack on headphones?

I want to record my guitar with Garageband but to also hear what i record on headphones. So i am using a USB mixer and today have purchased a USB hub, I have connected the mixer and the headphones to the hub but i either hear the sound or i can record but not both in the same time. Is this a limitation of the ipad or of the hub? What adaptor or hub should i purchase?

Thanks