I am completely unfamiliar with USB audio interfaces. My question is: if I buy a USB interface, do I still need an internal computer soundcard to use and record virtual instruments? Do I even need internal sound at all? Thank you.

 

Nope. *no*

The USB interface is the sound card. The major benefit is that an internal soundcard is in the noisiest area...the inside of your computer. Obviously moving it outside will be better to avoid this scenario.

 

just set up your default card in control panel

 

Yeah, probably a really confusing question. But the short answer is "No". Your Audio Hardware(unfortunately called "interface" these days) can be either internal or external. You can have one or the other, or both, or even 4 or 5 of 'em of either kind.

Most good affordable ones these days are external, though someday I may buy a really kickass internal one (less available, and therefore usually not as many affordable options for 'em). The good thing about the external ones are that you can plug microphones and guitars, etc. into them because they have XLR and 1/4" inputs on them.

External Example: Akai EIE Pro http://www.sweetwater.com/store/detail/EIEPro/

Internal Example: M-Audio Delta 10 http://www.m-audio.com/products/en_us/Delta1010LT.html

10 "Channels" can be achieved with virtual interface programs, so don't feel like you have to literally have 10 physical connectors on the soundcard to have those channels.. This can be achieved with a combo of software programs called "Jack"(link) and "Loopbe1" (link). I wanted to route Traktor output stuff through Ableton effects at one point, and it turns out I was okay with my sound card(Akai EIE) and did not have to buy a NI Audio 8 or 10, or whatever else, to get more "channels".

Not sure what "noise" there is regarding internal cards. In general, performance on internal ones is better than on the external ones (even USB 3.0), though USB is more flexible/versatile. I'd probably get an external if in doubt.

Hope that helps, and I hope this drawing might help...

 

You need to check that the interface/audio card is usb 2.0
There's a big difference between 1.0 and 2.0

I would recommend focusrite or presonus for a good one.