This question is coming up to us quite a lot so let us try our best to explain in simple terms how USB works. 

USB is a protocol that interfaces a HOST (think of it the brain) to a Device (think of it as an accessory). 

You would connect a HOST to a Device. You can't connect a Device to a Device. 

Now let's list some examples of accessory working in HOST and DEVICE modes. 

HOST modes: 

- PC

- Laptop

- Phone/tablet able to support "HOST" mode

DEVICE modes: 

- Mouse, Keyboard accessories

- USB audio interface such as miniDSP. 

As most of your already know, you can't connect a Mouse to a keyboard without a PC. Everybody agrees on this? 

So down to the question we get asked a lot: "Can I connect a miniDSP xxx  USB port directly to the USB port of my DAC?" 

The answer is....... No. :-) 

You can't connect a Mouse to Keyboard and you therefore can't connect a miniDSP (or any USB audio interface) to another USB audio interface as they are both "Devices". You need a USB HOST (E.g. a PC) to connect a USB device.(e.g. miniDSP)  

Hoping all this makes sense. You can easily find more detailed explanation online on how USB host vs Device mode works.