XLR Cables - Technical Discussion: Difference between revisions

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What does it mean to have "balanced" vs. "unbalanced cables and connections?

What does it mean to have "balanced" vs. "unbalanced" cables and connections?

'''Balanced''': What this really means is that there are TWO wires carrying a varying signal, not just one. There has to be a "reference", which is provided by the 'ground' -- hence a third wire. The advantage of a "balanced" signal is that one can get a better "signal-to-noise" ratio because the receiving amplifier is looking at the difference between the two signal wires, rather than just the difference between one wire and "ground". That's why a "balanced" system (balanced output, 3-wire cable, balanced receiving input) can be better at rejecting any "noise" which might exist between the 'sender' and the 'receiver' -- and the longer the cables, the more of a problem the "induced noise" might be.

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For this "antenna effect" to work, the cable must only have its shield connected at one end, not both. This *is* common practice with most good XLR cables, but it is far less common with 1/4" cables. That's why XLR cables are generally preferred for long distance runs ... even if being used for an "unbalanced" signal. Unless you take apart the 1/4" connectors at both ends to see how the shielding is connected (or not), you really can't reliably depend on mixing-and-matching 1/4" cables ... but you can (generally) depend on good XLR cables to be properly shielded.

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There are a lot more subtleties about cabling, but that's the (non-pictorial) essence of the wiring terms "balanced/unbalanced" and "shielded".

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'''''If the ground is common to both pieces of connected equipment, why would it matter if both ends of a shield were connected? Now I'm confused.'''''

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To further confuse things, the Wikipedia reference to [http://en.wikipedia.org/wiki/XLR_connector#XLR3_connectors EIA Standard RS-297-A] says that third pin (actually, numbered pin 1) is used for chassis ground -- but doesn't reference the SIGNAL ground at all -- but one of the referenced links points to a [http://www.clarkwire.com/PinOutXLRBalanced.htm manufacturer's diagram] which shows pin 1 as a SIGNAL connection, and the shell is not connected to chassis ground!

Ideally, the external shell is connected to the cable shielding at both ends, and is connected to an independent "shield ground path" on the equipment at both ends, so that the "antenna" (induced) currents from that cable shield never enter the "reference ground" (signal ground) used by the circuitry at each end of the cable.

Ideally, the external shell is connected to the cable shielding at both ends, and is connected to an independent "shield ground path" on the equipment at both ends, so that the "antenna" (induced) currents from that cable shield never enter the "reference ground" (signal ground) used by the circuitry at each end of the cable. All three pins on the connecter are connected; if pin 1 is not connected, that could be an unsafe cable to use!

However, as a user -- do you know what the manufacturer has done with the "shell/chassis" ground and the "signal ground"??? Not knowing that ... and knowing that manufacturers disagree on the best ~~practices~~ for doing so ... one can get all sorts of variations of grounding, as in Figure 5 in that [http://www.rane.com/note151.html Rane article].

However, as a user -- do you know what the manufacturer has done with the "shell/chassis" ground and the "signal ground"??? Not knowing that ... and knowing that manufacturers disagree on the best practises for doing so ... one can get all sorts of variations of grounding, as in Figure 5 in that [http://www.rane.com/note151.html Rane article].

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So, other than throwing up one's hands in frustration, what can we non-wiring-technician end-users do?

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Here is a pointer to a commentary on the standards -- even the professionals don't agree on the best and safest way to handle XLR connections, grounding, and shielding. [http://www.aes.org/standards/b_comments/comments-draft-aes48-xxxx.cfm (Comments on shielding/grounding standards.)]

[[Category:Reference]]

@@ Line 1: / Line 1: @@
-What does it mean to have "balanced" vs. "unbalanced cables and connections?
+What does it mean to have "balanced" vs. "unbalanced" cables and connections?
 '''Balanced''': What this really means is that there are TWO wires carrying a varying signal, not just one. There has to be a "reference", which is provided by the 'ground' -- hence a third wire. The advantage of a "balanced" signal is that one can get a better "signal-to-noise" ratio because the receiving amplifier is looking at the difference between the two signal wires, rather than just the difference between one wire and "ground". That's why a "balanced" system (balanced output, 3-wire cable, balanced receiving input) can be better at rejecting any "noise" which might exist between the 'sender' and the 'receiver' -- and the longer the cables, the more of a problem the "induced noise" might be.
@@ Line 13: / Line 13: @@
 For this "antenna effect" to work, the cable must only have its shield connected at one end, not both. This *is* common practice with most good XLR cables, but it is far less common with 1/4" cables. That's why XLR cables are generally preferred for long distance runs ... even if being used for an "unbalanced" signal. Unless you take apart the 1/4" connectors at both ends to see how the shielding is connected (or not), you really can't reliably depend on mixing-and-matching 1/4" cables ... but you can (generally) depend on good XLR cables to be properly shielded.
-=======================
+----
 There are a lot more subtleties about cabling, but that's the (non-pictorial) essence of the wiring terms "balanced/unbalanced" and "shielded".
-=======================
+----
 '''''If the ground is common to both pieces of connected equipment, why would it matter if both ends of a shield were connected? Now I'm confused.'''''
@@ Line 39: / Line 39: @@
 To further confuse things, the Wikipedia reference to [http://en.wikipedia.org/wiki/XLR_connector#XLR3_connectors EIA Standard RS-297-A] says that third pin (actually, numbered pin 1) is used for chassis ground -- but doesn't reference the SIGNAL ground at all -- but one of the referenced links points to a [http://www.clarkwire.com/PinOutXLRBalanced.htm manufacturer's diagram] which shows pin 1 as a SIGNAL connection, and the shell is not connected to chassis ground!
-Ideally, the external shell is connected to the cable shielding at both ends, and is connected to an independent "shield ground path" on the equipment at both ends, so that the "antenna" (induced) currents from that cable shield never enter the "reference ground" (signal ground) used by the circuitry at each end of the cable.
+Ideally, the external shell is connected to the cable shielding at both ends, and is connected to an independent "shield ground path" on the equipment at both ends, so that the "antenna" (induced) currents from that cable shield never enter the "reference ground" (signal ground) used by the circuitry at each end of the cable.  All three pins on the connecter are connected; if pin 1 is not connected, that could be an unsafe cable to use!
-However, as a user -- do you know what the manufacturer has done with the "shell/chassis" ground and the "signal ground"???  Not knowing that ... and knowing that manufacturers disagree on the best practices for doing so ... one can get all sorts of variations of grounding, as in Figure 5 in that [http://www.rane.com/note151.html Rane article].
+However, as a user -- do you know what the manufacturer has done with the "shell/chassis" ground and the "signal ground"???  Not knowing that ... and knowing that manufacturers disagree on the best practises for doing so ... one can get all sorts of variations of grounding, as in Figure 5 in that [http://www.rane.com/note151.html Rane article].
-=======================
+----
 So, other than throwing up one's hands in frustration, what can we non-wiring-technician end-users do?
@@ Line 54: / Line 54: @@
 Here is a pointer to a commentary on the standards -- even the professionals don't agree on the best and safest way to handle XLR connections, grounding, and shielding.  [http://www.aes.org/standards/b_comments/comments-draft-aes48-xxxx.cfm (Comments on shielding/grounding standards.)]
+{{:Balanced vs Unbalanced}}
 [[Category:Reference]]