Xlr output in guitar processor

Question

Could you point be out why XLR output is so important? I’m thinking to buy bass processor Zoom B3 or Boss gt-1b and first one has this output onboard.

Thanks everyone for your help!

Answer 1

XLR output is useful when connecting directly to mixing console or audio interface with XLR cable (rather than connecting to a guitar amplifier with instrument cable).

XLR connection is differential. The main advantage is that the ground can be disconnected (e.g. using switch on ZOOM unit) which helps to fight ground loop noise. Also XLR cable is more resistant to interference and typically will introduce less noise.

Answer 2

The physical format of the plug (XLR) is irrelevant. What is relevant is that the output is

• balanced and
• line-level

An XLR plug can be used for balanced or unbalanced signals and it can be line-level, instrument-level, or mic-level, or even high-voltage speaker-level. It doesn't even need to be analog audio at all, it could also be AES3 digital audio.

On the other hand, a balanced and line-level output can be TRS or XLR.

The physical format of the output doesn't tell you anything.

The output of the Zoom B3 is a line-level, balanced output. That is what is important, not the fact that it is physically an XLR output (although that is nice, too, since it is the de-facto standard for transporting analog audio signals in professional environments).

Balanced connections use differential signaling, where the original signal is transmitted over one wire, and the equal but opposite signal is transmitted over another wire. The two wires are kept in close proximity to each other (typically, they are twisted together into a twisted pair). Now, when external noise is introduced into the cable, the noise will be roughly the same on both wires.

At the receiving end, we receive on the two wires:

• the positive signal +S and the noise N
• the negative signal -S and the noise N

And we take the difference of the two wires:

  +S + N - (-S + N)
= +S + N + +S - N
= +S + +S + N - N
= 2S + N - N
= 2S

in other words: since we take the difference between the two wires but the noise introduced is roughly the same on each wire, the noise cancels out.

This allows transporting analog audio signals over relatively large distances with very little noise.

This differential signaling is used in many other applications, for example in Ethernet. In fact, because of the high demands of Gigabit Ethernet, Cat5e cables are typically much higher quality than standard audio cables, and because of the much bigger IT market compared to the pro audio market, they are also much cheaper (cents per meter for Cat5e compared to tens of cents per meter for microphone cables). And they contain 4 twisted pairs, so you can actually transport 4 audio signals on a single Cat5e cable for cheaper and with higher quality than you can through a microphone cable, and with a connector that has roughly the same footprint as a single XLR. (This is a nice trick to keep in mind when building small multicores.)