Audio or Video Over Cat5 Cable
You may want to send low level audio signals from room to room or system to system without using balanced cables. Most consumer equipment uses unbalanced RCA connectors and these must be sheilded to avoid hugh amounts of noise. There are however, Balun adapters that are prewired with RCA connectors and CAT5 RJ45 connectors that you can use. The real benefit is that this type of design can go 1000 feet without significant signal loss. It is also possible to send analog video and even digital signals this way. [Obviously not optical digital]
Here are some of the available configurations
There are many more configurations but they are basically the same use. You connect one adapter to your source. In my situation, that was the output channels of an audio mixer in the Listening room. Connect a CAT5 cable and run it to the other location. In my situation, i have several runs of CAT5 from the Listening room to the downstairs lab. Then connect the other end to another Balun, and then to the input channel of the target device. In my case this is a mixer that feeds the whole house system, and the lab.
The downside is of course that this run of CAT5 cannot be used as a conventional ethernet cable, at the same time it is being used for audio. But of course you can simply disconnect it and use it for other uses any time you want, say for a portable computer or something like that.