Patch bays come in a variety of sizes and types, the most common being a 48-point patch bay with standard TRS connectors. A 48 point patch bay has 24 inputs and 24 outputs on the front and back panels for a total of 96 jacks. When looking at the front panel, the top row jacks are the outputs and the bottom row jacks are the inputs. The jacks on the back panel correspond to those on the front. The various pieces of audio equipment are plugged into the jacks on the back and patch cords are used with the front jacks to make connections between those devices, much like a telecommunications switchboard.
The various pieces of equipment — microphones, instruments such as electric guitars or keyboards, monitor speakers and similar — are connected to the inputs and outputs on the back. These connections generally remain stationary and interconnections between the devices are managed using the inputs and outputs on the front via patch cords. Equipment is never plugged into the front jacks, only those on the back. Many, but not all, patch bays also have a kill switch, usually located prominently on the front panel. This is used to instantly shut the patch bay down in the event of unexpected feedback or other problems.
It is essential that those using a patch bay first take some time to carefully design the patch bay’s wiring scheme on paper, taking into account all pieces of equipment and their relationships to one another during recording. This is important because a wiring mistake while recording can result in extreme feedback that can damage the equipment or even your hearing. A patch bay schematic is generally created in the form of a flow chart. Because patch bays vary considerably, many come with special schematic sheets for the owner to use.
Although any number of connection schemes are possible, a basic patch bay scheme is as follows. An audio engineer connects a speaker, a microphone and an electric guitar to jacks on the back of the patch bay. The speaker is plugged into the first output jack, usually labeled A1, and the microphone and guitar are plugged into the first two input jacks, A1 and B1. Using a single patch cord, the engineer can then selectively route audio between the microphone or guitar outputs and the speaker input using the corresponding jacks on the front of the patch bay.
If you are working with fewer than 10 pieces of equipment, a patch bay is unlikely to be a worthwhile investment. Purchsing the patch bay, several patch cords and the cords required by each piece of equipment will become quite expensive. However, if you are using more than 10 pieces of equipment and are planning a series of complex recording sessions, a patch bay will come in handy. Although generally found in professional studios, many home users find that a patch bay makes recording with many pieces of equipment much easier.