The RCA jack
Single-ended audio means there’s only a one audio signal referenced to ground per channel. RCA jacks are used for single-ended audio.
The wiring of single-ended RCA jacks is relatively simple. There are 2 connections to the RCA jack: 1) The center pin carries the actual audio signal; and, 2) The outer shell connects to system ground. This is illustrated in the image below that closely mimics an actual RCA jack.
Wiring RCA Jacks to the V25
The recommended way to wire single-ended RCA inputs/outputs to the V25 is presented in the two diagrams below. The first diagram is a more abstract schematic representation while the second looks closer to the actual wiring to the boards. In either diagram we only terminating a single input and a single output to the left and right channels.
Before diving in with wiring your V25 boards, we highly recommend you study these diagrams until you understand the wiring scheme represented here.
The wiring diagram shown below is consistent with the schematic shown above and is provided to show where the wires need to be connected on the actual V25 boards. Note that this is only for a single input so the input is connected to the solder pads labeled RI1 and LI1 on each board. For additional inputs you would terminate the wires to solder pads RI2 and LI2 etc.
Alternatively you could also make the same terminations via the J5 pin header or some combination of the J5 header and the solder pads.
Lastly, 2 solder pads are provided on the V25 board for both the output (RO and LO) and the signal ground (RG and LG). These redundant pads are solely for convenience.