I had the same problem, but it went away when I switched to another hub.
bDeviceProtocol 1 Single TT
This might be the problem, the hub has only one Transaction Translator. The Transaction Translator is what translates USB1 to USB2.
When you have three USB1 devices (keyboard, mouse and sound card) competing for the lone Transaction Translator, the hub might struggle and start to drop packets. And lost packets in an audio stream is often heard as crackles.
My new hub is reported by lsusb as having bDeviceProtocol 2 TT per port
, each USB1 device I plug in has its own TT.
3. When I unplug the keyboard and mouse, the USB sound card was immediately producing good quality audio.
The Sound Card is then the only USB1 device connected to the hub and can have exclusive access to the Transaction Translator.
3. On the second USB hub, I connected USB Sound Card, USB Drive and my Android Phone.
Assuming both the drive and the phone are USB2, you now have only one USB1 device in need of the Transaction Translator, and presumably it can keep up.
The result is that USB Sound Card is producing good quality audio. This suggest that the keyboard and the mouse is causing the issue.
Seeing as the Sound Card works when it is the sole USB1 device connected to the hub, I would try to get my hands on a hub with multiple transaction translators.
There are known problems in the USB implementation on the RPi, especially when using isochronous transactions, as from a sound scard.