I'm not sure about powered hubs, but some people find that if you have DAC that's powered entirely by USB, you can improve the sound by using a battery power supply and a cable splitter. For example, Anker batteries are batteries with USB ports used for charging phones. If you get a USB Y-splitter and block the pin that carries power on the plug that goes into your laptop, all the power to the DAC comes from the battery and not from the laptop. I do this with my USB DAC. It doesn't make much difference, really, but it depends on the particular DAC model as well as on the laptop.
Only way I can see the ODAC improving from a powered usb hub is if the usb port you are using on your computer/laptop does not provide sufficient power. I can't hear the difference between my laptop or pc or office pc (powered usb hub). Sorta like the whole cable debate. Your ears hear what you want it to hear imo. Just my two cents.
I agree, but a decent PC power supply makes an awful supply for a DAC. For example in the below image the top trace is a 5v linear regulator supply, the bottom is the power coming out of the USB port on my PC, which happens to have a Corsair AX850 power supply feeding an Asus Sabertooth x79 motherboard. The real problem is the many sources of noise at various frequencies operating inside the computer.