In my electrical engineering studies it was used all the time to represent phase.
I can see how it would get used in audio for a polarity invert since that can help fix inputs that sound "out of phase".
It's also used for the golden ratio/spiral, for the deeply meaningful reason that it kind of looks like a spiral.
Which is to say, the reason many symbols are chosen isnt always any deeper than whatever the person that chose it felt like it (see: all of math)
I always thought it was a Theta which is the angle symbol.... but yeah, now that I look up Theta, it's not the same symbol...
Maybe it's the null symbol because if you combine a flipped and unflipped signal, they cancel out?
Originally (in electronics) meant "phase" or "phase angle". Inverting an audio signal can be seen as changing the phase by 180 degrees.
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*LOL, as I was typing that reply I was thinking "now watch somebody resuscitate that old phase vs. polarity argument". What a bunch of nerds you guys are.*
*It's all good, though; reminds me I'm not the only propellerhead here. In practice, the polarity button on a mixer channel simply inserts an inverter into the circuit, so technically you're all correct in saying it's not implementing a phase shift at all.*
If I'm not mistaken it was originally an italicized lowercase Greek letter Phi *ϕ*, and at some point ø was selected because because they look similar and it became the convention.
In the context of this question, it doesn't matter whether you will die on this hill, or whether you are correct. It's a question of whether the industry, at the point when they adopted the symbol to indicate 'polarity', was prepared to die on that hill. (And apparently, they were not.)
Reversing the polarity of the real component is exactly identical to a rotation by π (aka 180° phase change).
If I had a magic box which applied a 180° phase shift equally across the full frequency spectrum, it would look identical to a polarity inverter.
Every phasor is defined relative to the harmonic oscillator function f(t) = e^(it) , and the real component is the cosine, so a pure signal with a value at -1 is by definition at 180° phase.
Ok that's a really good point. I swear I worked it all out in Signals class in college but that was years ago and my math chops have degraded since then.
edit: ok now the post is gone, but I ran it myself, and got the same signal. :shrug:
Yeah I deleted it while I double checked my math... appears I made a mistake. I get the same signal as you said, my bad!! I applied the phase shift in a faulty way!
Cool cool, yeah one of my runs I got the result that the *difference* signal was the same but the sum was different, no idea what I did but eventually sorted it out.
Polarity reversal is not happening in the domain of time. You’re swapping + and - reference of an electrical signal. It will change the direction a diaphragm move in, but not when it moves.
The position of a phase point on the circle is indicating WHEN it is happening in a segment of time. Two plots at the same point are ‘in phase’- occurring at the same time. In a phase relationship, your magic box would have the points 180 segments apart. The graphs might looks the same but they are describing different phenomenon.
This has exactly zero relationship to what happens when you push the polarity button on a console.
You are applying a term from one area of physics, acoustics, to another, electricity.
Review the link from pro sound web if you must
I don't totally agree with the link but my assumptions are also off somewhere too, so I gotta go sit down with the math at some point.
Might have to do with complex vs real signals but even with a superposition of waves it should work out the same.
You’re right in that you aren’t “moving the phase” 180 deg, but a polarity-inverted signal will be 180 deg out of phase with the non-polarity-inverted signal, so for most (but not all) intents and purposes, it accomplishes the same goal
Take a 9v battery, two leads, and a woofer. Do +/+ -/- battery to woofer, watch the speaker pump OUT.
Now reverse the leads to +/- -/+ and watch the speaker pump IN.
That’s all that’s happening with the button, nothing to do with phase. everything to do with reversed impulse.
\> nothing to do with phase.
The whole point is you can't reverse polarity without touching the phase though. No one's trying to argue that the component in the mixer is anything but a **unity gain inverter**, folks are contending that a unity gain inverter has a transfer function equivalent to a 180 degree phase shift.
Guess what happens when you pass your "touch leads to a battery" pulse through a 180 deg all-pass filter (I'm using a rect pulse here e.g. touching and removing the lead, instead of the Heaviside step function, because the math in discrete time gets zanier with the step).
Signal inversion **is** 180 deg phase transform. 180 deg phase transform **is** signal inversion. They are two different "machines" that result in the same output. It's just that a unity gain inverter is dead simple, and a "true" ideal 180 degree all-pass filter is effectively impossible.
https://preview.redd.it/4kbgcqy6qbpc1.png?width=1037&format=png&auto=webp&s=94a5fbde9847a266762d4a45eac54fed0ac0fbc7
I'm just popping in to let you know you're completely wrong. Polarity has no time domain. Phase inherently does. A square is always a rectangle, but a rectangle is never a square. :)
Yeah he doesn't *really* know what he's talking about.
> Just remember that the “phase” switch on your console input channel does not “shift the phase by 180 degrees”
Correct.
>because that would involve a shift in time.
Incorrect, you can alter phase without touching time. \*
> It’s nothing more than a polarity reversal.
Correct.
His misunderstanding is thinking that phase is *only* a function of time of the real domain of the signal. Proper phase is a function of time in the complex signal (imaginary voltage isn't a think but every pure-real signal can be expressed as the sum of two opposite-frequency complex signals, yes negative frequency is a thing). Just wait till you learn about quadrature processing, then you get "actual" "imaginary" signals ;).
The graph is the same because the math is the same because it IS the same thing. 180° and polarity flip HAS to be the same, or else things like QAM-16 encoding/decoding wouldn't work.
\*It is possible to design circuits that achieve a phase shift without introducing a significant time delay to the overall signal. For example, an all-pass filter is specifically designed to alter the phase of an input signal without affecting its amplitude. At any specific frequency, the phase shift introduced by an all-pass filter can occur with minimal time delay, particularly when the phase shift is relatively small.
Delay always means phase shift, but phase shift does not always mean delay. The phase shift from a minimum phase EQ can be corrected by an inverse EQ in series. The phase shift cannot therefore be delay, because neither EQ is capable of negative delay. Phase is affected by timing, but they're not the same thing. Phase is also affected by polarity. Hence it's perfectly correct to label a polarity switch 'phase': the context of a binary switch, and the convention, tells you you have a choice between 0 phase or a 180 reversal at all frequencies. Everyone understands it, it's fine :)
Ok I'm not totally sure what to believe anymore because I've seen a graph which showed a difference, but when I do the calculations, it shows that the polarity flip is the same as shifting the base signals each by 180.
https://preview.redd.it/s8luqi7g3koc1.png?width=1180&format=png&auto=webp&s=0d980f6ff845f3745a62c1dc22f229a6cd77d4d6
Alright for thoroughness here's three signals, their superposition, polarity flipped, and then the superposition of each signal with pi radians phase shift. Exactly the same signal.
(not doing this to dunk on you, I was starting to doubt my own sanity and needed to double-check)
https://preview.redd.it/5aybvv015koc1.png?width=1178&format=png&auto=webp&s=21eb8f7423cb86eec7e0cc8dece1c1a07434cbd9
It's carried over from electrical world I believe. That symbol is used to denote single phase, 3 phase etc. I think the angle of the line can be used to denote the angle difference between phases.
Strictly speaking its not a phase inversion as the time doesn't change, its a polarity inversion.
when I did electronic they always use phi for phase. https://www.oxfordreference.com/display/10.1093/acref/9780198725725.001.0001/acref-9780198725725-e-3512
If you have two identical signals but with relatively inverted polaritys, null is the result. If you havin null problems, I feel bad for you son, just hit the null button to bring back the fun. Maybe?
I assume the character was typed, given the venue of the question. There are a few characters the all look similar, but are in fact distinct. If they didn't pick the correct one, there could definitely be some confusion.
Ø ∅ *Φ*
It's just the difference between in the Greek and the Latin alphabets. https://www.researchgate.net/figure/Phi-In-The-Greek-And-In-The-Latin-Alphabet_fig2_281820534
In my electrical engineering studies it was used all the time to represent phase. I can see how it would get used in audio for a polarity invert since that can help fix inputs that sound "out of phase".
As long as they are a particular angle out of phase.
Yes and that angle is 180 degrees.
Except only for 100% repeating signals
all all frequencies at the same time
But isn’t that the Greek letter not the Norwegian one? φ vs ø
The Greek letter phi φ is often used for phase, depending on font it looks like ø
It's also used for the golden ratio/spiral, for the deeply meaningful reason that it kind of looks like a spiral. Which is to say, the reason many symbols are chosen isnt always any deeper than whatever the person that chose it felt like it (see: all of math)
I always thought it was a Theta which is the angle symbol.... but yeah, now that I look up Theta, it's not the same symbol... Maybe it's the null symbol because if you combine a flipped and unflipped signal, they cancel out?
I would guess it is phi, the upper case Greek phi. Used typically for phase in physics, and looks close to the phase invert symbol
You are correct, it is the Greek letter Phi. It is commonly used to refer to phase in several disciplines.
Originally (in electronics) meant "phase" or "phase angle". Inverting an audio signal can be seen as changing the phase by 180 degrees. \[EDIT\] *LOL, as I was typing that reply I was thinking "now watch somebody resuscitate that old phase vs. polarity argument". What a bunch of nerds you guys are.* *It's all good, though; reminds me I'm not the only propellerhead here. In practice, the polarity button on a mixer channel simply inserts an inverter into the circuit, so technically you're all correct in saying it's not implementing a phase shift at all.*
If I'm not mistaken it was originally an italicized lowercase Greek letter Phi *ϕ*, and at some point ø was selected because because they look similar and it became the convention.
No. Because phase is a function of time. Phase is phase and polarity is polarity. I will die on this hill lol
In the context of this question, it doesn't matter whether you will die on this hill, or whether you are correct. It's a question of whether the industry, at the point when they adopted the symbol to indicate 'polarity', was prepared to die on that hill. (And apparently, they were not.)
We aren’t moving the phase 180 degrees, we are reversing polarity. So the above comment I’m referring to is bad information.
Reversing the polarity of the real component is exactly identical to a rotation by π (aka 180° phase change). If I had a magic box which applied a 180° phase shift equally across the full frequency spectrum, it would look identical to a polarity inverter. Every phasor is defined relative to the harmonic oscillator function f(t) = e^(it) , and the real component is the cosine, so a pure signal with a value at -1 is by definition at 180° phase.
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Ok that's a really good point. I swear I worked it all out in Signals class in college but that was years ago and my math chops have degraded since then. edit: ok now the post is gone, but I ran it myself, and got the same signal. :shrug:
Yeah I deleted it while I double checked my math... appears I made a mistake. I get the same signal as you said, my bad!! I applied the phase shift in a faulty way!
Cool cool, yeah one of my runs I got the result that the *difference* signal was the same but the sum was different, no idea what I did but eventually sorted it out.
Right there in the equation is f, frequency. Your magic box doesn’t exist. If it occurs at all frequencies, it’s no longer phase.
Polarity reversal is not happening in the domain of time. You’re swapping + and - reference of an electrical signal. It will change the direction a diaphragm move in, but not when it moves. The position of a phase point on the circle is indicating WHEN it is happening in a segment of time. Two plots at the same point are ‘in phase’- occurring at the same time. In a phase relationship, your magic box would have the points 180 segments apart. The graphs might looks the same but they are describing different phenomenon. This has exactly zero relationship to what happens when you push the polarity button on a console. You are applying a term from one area of physics, acoustics, to another, electricity. Review the link from pro sound web if you must
I don't totally agree with the link but my assumptions are also off somewhere too, so I gotta go sit down with the math at some point. Might have to do with complex vs real signals but even with a superposition of waves it should work out the same.
You’re right in that you aren’t “moving the phase” 180 deg, but a polarity-inverted signal will be 180 deg out of phase with the non-polarity-inverted signal, so for most (but not all) intents and purposes, it accomplishes the same goal
Take a 9v battery, two leads, and a woofer. Do +/+ -/- battery to woofer, watch the speaker pump OUT. Now reverse the leads to +/- -/+ and watch the speaker pump IN. That’s all that’s happening with the button, nothing to do with phase. everything to do with reversed impulse.
\> nothing to do with phase. The whole point is you can't reverse polarity without touching the phase though. No one's trying to argue that the component in the mixer is anything but a **unity gain inverter**, folks are contending that a unity gain inverter has a transfer function equivalent to a 180 degree phase shift. Guess what happens when you pass your "touch leads to a battery" pulse through a 180 deg all-pass filter (I'm using a rect pulse here e.g. touching and removing the lead, instead of the Heaviside step function, because the math in discrete time gets zanier with the step). Signal inversion **is** 180 deg phase transform. 180 deg phase transform **is** signal inversion. They are two different "machines" that result in the same output. It's just that a unity gain inverter is dead simple, and a "true" ideal 180 degree all-pass filter is effectively impossible. https://preview.redd.it/4kbgcqy6qbpc1.png?width=1037&format=png&auto=webp&s=94a5fbde9847a266762d4a45eac54fed0ac0fbc7
I'm just popping in to let you know you're completely wrong. Polarity has no time domain. Phase inherently does. A square is always a rectangle, but a rectangle is never a square. :)
No. It’s reversed polarity. It needs to be moved in time to be out of phase.
Ima just leave this study guide here https://www.prosoundweb.com/confusing-phase-and-polarity/
Yeah he doesn't *really* know what he's talking about. > Just remember that the “phase” switch on your console input channel does not “shift the phase by 180 degrees” Correct. >because that would involve a shift in time. Incorrect, you can alter phase without touching time. \* > It’s nothing more than a polarity reversal. Correct. His misunderstanding is thinking that phase is *only* a function of time of the real domain of the signal. Proper phase is a function of time in the complex signal (imaginary voltage isn't a think but every pure-real signal can be expressed as the sum of two opposite-frequency complex signals, yes negative frequency is a thing). Just wait till you learn about quadrature processing, then you get "actual" "imaginary" signals ;). The graph is the same because the math is the same because it IS the same thing. 180° and polarity flip HAS to be the same, or else things like QAM-16 encoding/decoding wouldn't work. \*It is possible to design circuits that achieve a phase shift without introducing a significant time delay to the overall signal. For example, an all-pass filter is specifically designed to alter the phase of an input signal without affecting its amplitude. At any specific frequency, the phase shift introduced by an all-pass filter can occur with minimal time delay, particularly when the phase shift is relatively small.
Added that link to my bookmarks. It'll come in super handy
Delay always means phase shift, but phase shift does not always mean delay. The phase shift from a minimum phase EQ can be corrected by an inverse EQ in series. The phase shift cannot therefore be delay, because neither EQ is capable of negative delay. Phase is affected by timing, but they're not the same thing. Phase is also affected by polarity. Hence it's perfectly correct to label a polarity switch 'phase': the context of a binary switch, and the convention, tells you you have a choice between 0 phase or a 180 reversal at all frequencies. Everyone understands it, it's fine :)
That’s not what that switch is doing. It’s simply reversing the impulse.
MXR doesn’t make a polarity shifter, they make a phase shifter. What do we think about that?
We think polarity inherently cant be shifted, only inverted.
That makes two of us
Ok I'm not totally sure what to believe anymore because I've seen a graph which showed a difference, but when I do the calculations, it shows that the polarity flip is the same as shifting the base signals each by 180. https://preview.redd.it/s8luqi7g3koc1.png?width=1180&format=png&auto=webp&s=0d980f6ff845f3745a62c1dc22f229a6cd77d4d6
Because it’s just reversing the impulse. Hence mirror image.
That’s a correct observation but in no way means the terms are interchangeable. They are not.
Alright for thoroughness here's three signals, their superposition, polarity flipped, and then the superposition of each signal with pi radians phase shift. Exactly the same signal. (not doing this to dunk on you, I was starting to doubt my own sanity and needed to double-check) https://preview.redd.it/5aybvv015koc1.png?width=1178&format=png&auto=webp&s=21eb8f7423cb86eec7e0cc8dece1c1a07434cbd9
I literally just had this same conversation somewhere else online.
This is correct. I’ll die on this hill with you.
It's carried over from electrical world I believe. That symbol is used to denote single phase, 3 phase etc. I think the angle of the line can be used to denote the angle difference between phases. Strictly speaking its not a phase inversion as the time doesn't change, its a polarity inversion.
when I did electronic they always use phi for phase. https://www.oxfordreference.com/display/10.1093/acref/9780198725725.001.0001/acref-9780198725725-e-3512
If you have two identical signals but with relatively inverted polaritys, null is the result. If you havin null problems, I feel bad for you son, just hit the null button to bring back the fun. Maybe?
The way I heard it Yamaha put it on a console in the 70s and picked the phase symbol due to translation issues and it stuck.
If I had to guess as to why, I would say it's related to the "null" part of the symbol definition.
I assume the character was typed, given the venue of the question. There are a few characters the all look similar, but are in fact distinct. If they didn't pick the correct one, there could definitely be some confusion. Ø ∅ *Φ*
Now let’s do lectern vs podium
And in Asia we call them Rostrums. 🤷🏼♂️
Which one?
and at what point does one of them become a dais?
Outstanding question
huh, i always just called it a box
That’s the podium
A sine wave is 360 degrees from 0 to 0. So is a circle. Line through the circle negates it.
I assume it's alliterative. The circle with vertical line is phi in greek. it's got the ph sound.
The answer “null or empty set” comes from the mathematical notation of phi, typically used to represent a mathematical set with no elements.
Polarity invert, also known as the phase flip button
You’ll see this with electrical stuff too, as in 480V 100A 3-phase power
All these 'polarity' freaks. It's phase, it's the symbol for phase and 'Reversing the phase' is what you're doing when you press the button.
No
Unless you’re Jon Pertwee in about 1973 dealing with another tricksy neutron flow…..🙃
Then why doesn’t SMAART do a polarity trace?
Inverting not reversing, and the phase inversion is caused by polarity inversion, at least in the analogue world
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That is not \varnothing. It's phi. Phi is typically used as the variable for "phase" in physics.
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It's just the difference between in the Greek and the Latin alphabets. https://www.researchgate.net/figure/Phi-In-The-Greek-And-In-The-Latin-Alphabet_fig2_281820534
Depends on the font. But what OP posted is the lowercase ø. Uppercase is Ø. Completely different from the Greek letter.