USB 5V power can be equally noisy, even from a powered hub, so that argument doesn’t make any sense. PCIe has a high current 12V rail available that has much more margin than USB for filtering with an LDO and run your signal chain well above the noise floor of the components.
Besides, Asus Xonar as in the picture can take 12V from a drive connector to bypass the motherboard PCIe 12V “just in case”.
USB 5V power can be equally noisy, even from a powered hub, so that argument doesn’t make any sense. PCIe has a high current 12V rail available that has much more margin than USB for filtering with an LDO and run your signal chain well above the noise floor of the components.
Besides, Asus Xonar as in the picture can take 12V from a drive connector to bypass the motherboard PCIe 12V “just in case”.