XLR vs RCA

I am not an expert in this area, but here's what I know.

In a single-ended setup, there is one wire which caries alle the audio signal, and the hield which is usually tied to ground. The shield is there to keep RF noise out. This solution is not 100% perfect; on longer runs of cable, for example, you could still get some noise on the signal line, with no way to get rid of it.

In a balanced setup, there are a number of signals on the cable. I believe it works something like this: Hot pin carries the signal, and the cold pin carries the inverse of the signal. If there is noise on the line, it will offset the hot and cold evenly, and therefor you can get rid of it on the other end of the line, but I have forgotten exactly how. In essence, the system also does not need a ground, so it helps with ground loops. (Like I said, not an expert ;)

On truly balanced equipment, many people seem to agree that balanced cables work best. I have a Mark Levinson pre and power amp; they are interconnected with balanced cables, and the result sounds a bit more pleasing than when I use single ended cables.

On the other hand, my Sony SCD-1 is connected to the preamp with balanced cables, but it does not sound quite as pleasing as it does with single ended cables. I am told this is because the Sony is internally not truly balanced, rather they use a converter to change the single ended signal to a balanced one.

In my opinion, the best thing to do is to listen to either setup and see what's best. I did not do that with my SCD-1 since I assumed balanced was better. Wrong choice.

Niels.

All other things being equal balanced connections in a truly balanced system should be better.

Balanced connections have two signals, a positive and a negative signal, which are inverted versions of each other. They carry the signal currents. At the destination, these are subtracted from each other to create the signal. Any noise that is the same on both cables will be subtracted-out. There is also usually a ground that does not carry signal current - it's function is to force the grounds in the two components to the same potential. The ground conductor can be a wire or an overall shield surrounding the other two signal conductors.

Unbalanced or Single-Ended connections have a signal and a ground RETURN. Both of these carry current and the signal is driven at the source with the return current flowing back to the source on the ground conductor. The ground conductor can be a wire or a coaxial shield, depending on the design.

XLR's are superior is a number of ways. First, they are locking, so they won't pull loose. Second, they have male and female, so you can't accidently plug them in backwards. Third, they use a two signal system comprising an uninverted and an inverted signal plus a third wire ground, which carries no signal current. This "balanced" or "differential" signalling system allows the receiving component to have better noise rejection than with Single-Ended (SE) signalling. This is possible because the receiving component subtracts the + and - signals to get the signal that is used in the component. If there is any noise that is common to both + and -, this will be eliminated by the subtraction process. This is referred to as "common-mode" noise, which can include 60 Hz hum, Schott noise, RFI etc...

The thing that you need to be aware of is that all designers do not have good designs for Balanced inputs and outputs. To determine which of SE and Balanced sounds better, you need to listen to both on a given component and choose the one that sounds best.

Better coherence and musicality with SE rather than XLRs? Thoughts?

I am with Warrenh. Even though Audioengr's points are valid, the last one is the biggest concern with balanced systems, the impossibility of designing a truly balanced system.

A system that is balanced from beginning to end is actually two chains of amplification. From source to preamp to power amp you have one string of amplifiers amplifying the inverted signal and a different string of amplifiers amplifying the non-inverted. These two signals are combined at the speaker. Even though they should be the same, with tolerances in components it is impossible to build two identical amplifiers.

It is highly unlikely that both signals will be treated exactly the same throughout this process so the reconstructed signal at the speakers is distorted. Yes, there are distortions in single ended systems like in all systems, but this one introduced by the balanced systems is not present in a single ended system.

Also, digital signals start out being single ended on the disc and must be converted to balanced somewhere along the path. This is another source of distortion.

As for noise rejection, balanced does have the theoretical upper hand on long lengths of cable. But with cable lengths and the amplitude of the signals in a typical system you could not tell any difference.