At the heart of 18i8 is a set of four Focusrite mic preamps with up to 60dB gain, designed specifically for Focusrite's computer audio interfaces. The first two inputs offer Mic/Line/Instrument on universal XLR/TRS connectors, while inputs 3 and 4 offer Mic/Line capability on universal XLRs-all four are on the front panel with pads and 48V phantom power. Four more line inputs are provided on TRS connectors. An ADAT optical digital connector provides eight additional digital inputs that can also be used with external mic preamps like Focusrite's OctoPre Mk II (sold separately) to increase the number of mic inputs the 18i8 can handle to 12. A stereo S/PDIF coaxial input is also included. On the output side, there are two TRS monitor outputs, stereo S/PDIF coax, and two independent stereo headphone outputs, each with their own volume knob so both the artist and the engineer can control their own personal monitoring. All analog inputs and outputs have their own connectors, so there is no need for breakout cables, and all feature Focusrite precision 24-bit, 96kHz sampling A/D and D/A conversion to get the most accurate signal possible into and out of recording applications on Windows, Mac and now iOS apps.