Common mode, differential mode: Difference between revisions
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There are a few areas where it would've been nice if it were standard - like consumer audio systems. | There are a few areas where it would've been nice if it were standard - like consumer audio systems. | ||
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==== | ===Perhaps-necessary clarification=== | ||
====Distinction between common mode, differential mode, single sided==== | |||
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Differential mode is a voltage difference | |||
: without tying either to a known level, without a shared reference | |||
: also meaning these wires are dedicated to one signal | |||
Common mode is a voltage difference | |||
: tying one to a known level | |||
: probably a reference reused for multiple signals | |||
Single sided means a signal is present on one wire and not another | |||
: which seems to describe common-mode reality | |||
: but can also be true in differential | |||
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====Differential in more depth==== | |||
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There are some related yet distinct concepts here: | There are some related yet distinct concepts here: | ||
* '''differential signalling''' | * '''differential signalling''' |
Revision as of 12:51, 17 September 2023
Common mode versus differential mode is about communicating a signal electrically, usually as a voltage signal.
Theoretical side
Common mode
Common mode signalling points at a situation where you have
- a reference conductor, which both ends of this communication have in common
- often called "signal common".
- a conductor for a signal
And the signal is the voltage difference between the two.
Differential mode / differential signalling
Perhaps-necessary clarification
Distinction between common mode, differential mode, single sided
Differential in more depth
Single ended
Single-ended signalling basically means all the signal is on one wire, none on any other.(verify)
A lot of the time, single-ended is used as a near-synonym for common mode.
And fair enough, common mode basically implies single ended, in that there is typically a signal common, used as a reference for one or more signals, which is usually tied to some fixed level (like ground).
Yet single-ended does not necessarily imply common-mode reference.
While introductions to XLR make a big kerfuffle over sending signal/2 and -signal/2 on the two wires, it is entirely valid to send the signal on one wire and nothing on the other (which you'd easily call signle-ended), because after differential interpretation this implies the same signal at the other end and the same amount of noise reduction.
In fact, doing this is moderately common(verify) because it is a little simpler component-wise.
If a distinction is made between single ended and common mode, single-ended often refers more to the concept, common mode more to electrical reality of conductors.
Both single-ended and common mode are mainly contrasted with differential mode
Practical side
Balanced audio / pro audio
See Music_-_studio_and_stage_notes#Notes_on_balanced_audio
Comparisons
See also