It’s very easy to assume that if your equipment has both XLR and RCA connections, that XLR connections are going to offer the better sounding audio result. This is not always the case and depends on a number of factors.
The XLR connection carries a balanced signal. The “hot” pin carries the signal, the “cold” pin also carries the signal but this signal is inverted (a mirror image of the “hot”) and the third pin carries the earth. At the receiving equipment, any noise that is common to both the hot and cold pins is cancelled out. This is particularly beneficial in recording studios where long runs of cable are often needed to carry the small voltages that make up the audio signal generated by a microphone over very long runs of cable (say 10+ metres).
In a Hi-Fi system though, where the longest interconnect is likely 0.5 to 1.5 metre, the need for XLR connections has questionable benefits.
The most important thing though is sound quality, and this is harder to be certain about. Our many years of experience is that there are source system components, whether they be CD players or AV Pre-amplifiers where the XLR connection produces a better sound than the RCA connection. There are also system source components where the opposite is true, producing a better sound from the RCA connection.
So with any system that has both XLR and RCA connections, we would recommend that you try both connections and decide for yourself which is the better sounding connection for your source component.
Source component equipment that only has RCA sockets can be connected to equipment that only has XLR sockets. This is achieved by connecting the signal from the centre pin of the RCA plug to the “hot” pin of the XLR, and the earth to the earth pin. In the same way, It is also possible to produce XLR to RCA cables.
A point of important note. Some XLR source equipment specifies a higher voltage signal than RCA outputs, up to 4 volts for the XLR and typically 2 volts for an RCA output. So if for instance, you were using a CD player with XLR output to an amplifier with RCA inputs, you could experience the extra signal strength overdriving the RCA input on the amplifier. The problem being that this will give you reduced control over the amplifier gain and in many cases results in harsh and fatiguing audio. This can be resolved by placing an attenuator to reduce the signal strength in the cable path.