ART's SPLITMix 4 can send one audio source to 4 outputs -- or mix 4 sources down to one output, with individual volume control. All jacks are stereo/mono.
No +48V phantom power on your mixer? Add this in-line phantom power supply with XLR input and output, and you'll have the power you need for condenser mics.
Plugging consumer gear into a pro audio setup? Convert an RCA or 1/8" stereo source to balanced XLR -- and vice versa -- with ART's noise-free adapter box.