Matters Concerning Audio - A Practical Guide to Video and Audio Compression - page 150

The MOTU FireWire 828 and similar hardware products are not too expensive; there
are also alternative products made by AJA and M-Audio, who provide audio input and
conversion solutions too. There are several different models to choose from in the AJA Io
FireWire interface family of products according to what your needs are.
M-Audio and Focusrite also make useful hardware. Certainly there are many other
alternatives, and a search through the products available from your audio retail outlet will
suggest some other alternatives.
FireWire is certainly a good choice because the throughput is sufficient to support the
highest sample rate, bit size, and number of channels you are likely to want. For amateur
or hobbyist requirements, USB is feasible but you may run out of capacity if you try to
grab too many channels at once.
The entire audio mixing process in a studio is now available inside a desktop system.
You simply have to get the sound in there in the first place. Figure 7-3 illustrates a MOTU
896 interface. M-Audio and other manufacturers make comparable units.
The MOTU 896 will sample 8 channels with 24 bits of resolution at 192 KHz. The
rack-mounted unit has 8 outputs as well, so that offers some interesting possibilities for
using it as part of a studio infrastructure. This unit also supports AES audio and SPDIF
in/out via an optical interface.

7.3.4 Digital Audio via SPDIF

This is derived from the optical connectors that were deployed on hi-fi equipment when
CD players were first introduced. The concept was that you would buy a high-end CD
player mechanism and then separately install a digital-to-analog converter, or perhaps
your very expensive hi-fi amplifier would have one built in. The SPDIF connection uses a
short piece of optical fibre. It was popularized by DAT players that seem to have gone out
of fashion now that you can record straight to your hard disk.
The SPDIF interface is used by semi-professional and professional sound engineers
and is reasonably common in situations where you want to connect some high-quality
audio equipment together.

Figure 7-3 FireWire 896 HD audio interface. Source: Image courtesy of MOTU.