Conference Room Theater
Ideally, a presenter would be able to use the A/V system for a slide show from a computer (potentially with a sound track) and talk over it with a wireless microphone. However, most receivers only allow a single input source to be selected. I have not been able to find an A/V receiver that would let me mix a microphone with the 7.1 sound system and watch a slide show from a computer video input. Do you have any suggestions?
For this application, I would get an AVR with multizone capabilities that lets you select one input for the main zone and another input for a remote zonemost multizone AVRs provide this functionality. In your case, both "zones" would be in the conference roomthe main zone would feed a 5.1 or 7.1 speaker system and the remote zone would feed an additional speaker in the same room. (If you really want 7.1 plus a microphone, you'll need a fairly high-end AVR with nine channels of amplification. If it were me, I'd go with 5.1 plus a mic, which would mean a less-expensive AVR with seven channels of amplification.)
You would connect the computer's audio and video output to one of the AVR's inputs and the microphone to another input. Virtually no consumer AVRs have an actual microphone input (other than the one used to auto-calibrate the AVR's settings), so a professional mic with XLR connector won't work, but a cheapie mic with a quarter-inch or RCA connector should work okay. If it has a quarter-inch plug, you'll need an RCA adaptor, since no AVRs have quarter-inch inputs.
Then, select the computer's input for the main zone and the microphone's input for the remote zone. The mic signal won't be heard from the same speakers as the computer audio, but it will be heard from the additional speaker in the room. Just make sure that the microphone is not directly in front of any speaker to avoid feedback.
If you have an A/V question, please send it to firstname.lastname@example.org.