Citation:
the Onyx FireWire Card is a true first. This user-installable 24-bit/96kHz card transforms the Onyx 1220, 1620 and 1640 mixers into fantastic-sounding digital audio interfaces capable of sending up to 18 channels of audio to your Mac or PC — without the need for additional converter boxes or hardware. Thanks to the use of flagship Onyx mic preamps, superior analog circuitry, and class-leading A/D converters, Onyx mixers with FireWire rival the sound quality of dedicated audio interfaces costing many times more. Not to mention the simplicity of plugging in up to 16 microphones and sending them directly from the mixer to your computer... and monitoring a stereo mix back through the mixer.
The Onyx FireWire Card allows you to stream up to 18 channels of 24-bit digital audio to your Mac (OSX 10.3.5 or greater) or PC (Win XP). These show up in your audio software as 16 individual audio inputs, plus a stereo L/R mix. You can also send two channels of audio back from the computer to the mixer for monitoring purposes.