These particular cards have regular analog audio outputs. There are some new, cool devices that transmit the audio signals directly via Ethernet.
Sometimes these analog outputs go directly to the amp channel(s), when some intermediate processing is required they are usually routed through a digital signal processor before then going to the amp. The DSP can provide additional routing, EQ, paging, muting, whatever is required by the application. A lot of the larger DSPs today can also handle audio signals directly via Ethernet, so if you have sources with the capability noted above, there is no need for individual analog wiring. In fact there are amplifiers and powered speakers available that can accept their inputs directly via Ethernet. This equipment is usually more expensive, but after considering the labor involved in wiring up hundreds of analog audio circuits as compared to relatively few RJ45 connections, the flexibility and labor savings can be well worth it.
The amps are usually located, well, in the rack room with the rest of the equipment.
