Phase/Polarity....Whatevah!!!!

[RAMI]

I have a question about polarity (I think in this case, that's the correct term).

From what I understand, a signal can only be out of phase in relation to ANOTHER SIGNAL, no??? (If that's not an accurate statement, then I don't think my next question will matter.)

So, if a signal can only be out of phase with another instrument, how come when I flip the polarity switch on my pre-amp, it CHANGES the sound of the mic to a thinner "out of phase" sound all by itself???

Do I answer my own question by acknowledging that "phase" and "polarity" aren't the same thing???

 

[MCI2424]

I have a question about polarity (I think in this case, that's the correct term).

From what I understand, a signal can only be out of phase in relation to ANOTHER SIGNAL, no??? (If that's not an accurate statement, then I don't think my next question will matter.)

So, if a signal can only be out of phase with another instrument, how come when I flip the polarity switch on my pre-amp, it CHANGES the sound of the mic to a thinner "out of phase" sound all by itself???

Do I answer my own question by acknowledging that "phase" and "polarity" aren't the same thing???

It depends on the room. Try it in a really large room where there are no reflections and the sound will be the same.

Now, if you have other problems, that would be a different issue. Are your speakers in phase? Without being there, this would be a tough one to troubleshoot.

Oh, BTW: Phase and polarity are not the same thing

 

[SouthSIDE Glen]

Phase and polarity are not the same thing, but that doesn't answer what you are hearing. Theoretically, neither one on it's own should cause an audible difference unless as you say, it is mixed with something else.

The question I have, Rami, is do you hear a difference if you do a polarity flip of the track in your DAW? I'll bet you don't. In which case I'd look at your preamp as a possible culprit here. Why a simple polarity inversion circuit in *any* preamp should cause such a coloration change, I don't know; but then again circuit design is not my long suit.

G.

 

[RAMI]

"phase" and "polarity" aren't the same thing???

Oh, BTW: Phase and polarity are not the same thing

Phase and polarity are not the same thing,

OK.....moving on.....



Glen, good advice. I never thought of the fact that it could be the pre-amp itself. I'll try the same thing in my 2488 and also in my computer and compare.

 

[mixsit]

So, if a signal can only be out of phase with another instrument, how come when I flip the polarity switch on my pre-amp, it CHANGES the sound of the mic to a thinner "out of phase" sound all by itself???

Could this be the sound of your voice in headphones here? There polarity does mater because of the mix of what's coming through your head vs the cans.

a quickie..
For polarity imagine a sine wave with a mirror image of it's self below it. Peaks on one are dips on the other.
For phase, in both images peaks and dips go the same way -Aligned they add volume.
Now slide one over. ('Slide' is time.) A little slide, a little cancellation, more slide, more cancellation. At some point in time they miss-align 100% and act like 'out of polarity' -but only at that frequency.

 

[RAMI]

Could this be the sound of your voice in headphones here? There polarity does mater because of the mix of what's comming through your head vs the cans.

Bingo!!! I only noticed it in headphones. Good call, Mixsit!

So this is normal in phones then????

 

[mixsit]

Yep. The 'phone, and the 'bone.

 

[RAMI]

Yep. The 'phone, and the 'bone.

Ah yes....the old phone-bone.

Thanx man.

 

[SouthSIDE Glen]

Mixsit, this is a new one on me. Could you dive into it a little more? I don't understand how it would make a difference because neither your phone or your bone knows or cares about whether a signal starts by going up or by going down. Assuming the polarity change is the same in both channels, I don't see how it would make a difference. What am I missing here?

G.

 

[NL5]

Mixsit, this is a new one on me. Could you dive into it a little more? I don't understand how it would make a difference because neither your phone or your bone knows or cares about whether a signal starts by going up or by going down. Assuming the polarity change is the same in both channels, I don't see how it would make a difference. What am I missing here?

G.

Yeah, I'll have to give this a try in a few.

Rami - you are listening to JUST the vox. No verb, no backing track, etc.....???

 

[RAMI]

Rami - you are listening to JUST the vox. No verb, no backing track, etc.....???

Right. Just vocals, solo-d for that matter, with no effects. When I engage or dis-engage the polarity button, the sound definitely changes. Not drastically, but noticeably thinner and slightly wash-y.

 

[mixsit]

The message you have entered is too short. Please lengthen your message to at least 10 characters.

 

[mixsit]

In my best Inspector Clouseau..Ah yes, the old 'Phone Bone ploy..''

Put the phones on, up close on the mic now, do a nice low Bing Crosby swoop'.
As I understand it the phones block the air path to the ear and the path from the mic can be out with the path through your head. (In the lows mostly.

 

[dualflip]

I have a question about polarity (I think in this case, that's the correct term).

From what I understand, a signal can only be out of phase in relation to ANOTHER SIGNAL, no??? (If that's not an accurate statement, then I don't think my next question will matter.)

So, if a signal can only be out of phase with another instrument, how come when I flip the polarity switch on my pre-amp, it CHANGES the sound of the mic to a thinner "out of phase" sound all by itself???

Do I answer my own question by acknowledging that "phase" and "polarity" aren't the same thing???

Phase in fact is considered as a shift in time, so when you have a 180 degree phase shift you in fact have the opposite polarity. But polarity is in fact other thing because for example, lets say you have 2 sine waves and you change the phase 180 degrees on one of them, youll be ending with the opposite polarity of one of the sine waves with respect to the other but there will also be a delay on one of them because theres a time shift... i dont know if i make myself clear.

Regarding the preamp button known as phase in fact its polarity, meaning that it only inverts the wave but with out shifting the time of the wave. For example if you have a loudspeaker, and you plug the + wire on the - terminal, and the - wire on the + terminal, you are switching polarity not phase and thats what the preamp button does. In another example if you have two loudspeakers but one of them has a delay of lets say 1ms in respect to the other, then youll have a phase shift of "X" degrees, depending on the delay of one of the speakers, you might end up with a 180 degree shift in one of the speakers wich corresponds to the opposite polarity of the other speaker.

 

[RAMI]

I have a question about polarity

how come when I flip the polarity switch on my pre-amp,

When I engage or dis-engage the polarity button,

Regarding the preamp button known as phase in fact its polarity,

Thanx for the info.....

 

[SouthSIDE Glen]

Put the phones on, up close on the mic now, do a nice low Bing Crosby swoop'.
As I understand it the phones block the air path to the ear and the path from the mic can be out with the path through your head. (In the lows mostly.

Ahhh, you're talking about live monitoring of your own singing. I missed that. OK, I can see that. There you *do* have two sources, one's own voice through bone conduction, and one's voices as heard through the mic path. And yeah, I can see where there would be potential phase cancellation issues there. However, If Rami is just listening to playback of a recording (or live from someone else singing), polarity inversion in and of itself should have no audible effect at all, even in cans.

Phase in fact is considered as a shift in time, so when you have a 180 degree phase shift you in fact have the opposite polarity.

True only if there is no DC offset in the signal. Granted, 99 times out of a hundred, there won't be offset (unless you're going through a stock laptop soundcard, in which case all bets are off .) But, the real fact is that a 180° phase change means a change of phase angle around the signal's rest voltage, whereas a polarity inversion means a similar change of phase angle around 0DC. Just because a lack of DC offset makes them appear the same, does not make them the same - or at least they will be measurably the same only if there is no offset. But just throw even a millivolt of offset into the signal, and they will differ.

But polarity is in fact other thing because for example, lets say you have 2 sine waves and you change the phase 180 degrees on one of them, youll be ending with the opposite polarity of one of the sine waves with respect to the other but there will also be a delay on one of them because theres a time shift.

This is not necessarily true. What you are describing is a phase shift, or - as I personally prefer to call it - a phase rotation. This rotation happens in time, which does indeed, by definition, make that a time-dependent process.

But it is entirely possible to change phase independent of the time variable; i.e. to have instantaneous phase change without having to shift position in time. Granted, not by sliding a waveform around on a timeline. But by executing a simple formula V2 = -V1 + Vr, where V2 is the new voltage value, V1 is the original voltage value, and Vr is the signal rest voltage or offset.

G.

 

[RAMI]

However, If Rami is just listening to playback of a recording (or live from someone else singing), polarity inversion in and of itself should have no audible effect at all, even in cans.

Sorry Glen, I should have been more clear. I've only noticed while monitoring my own voice live, not on playback. Thanx for your last post, combined Mixit's info, that pretty much explains it.

Thanx guys.

 

[SouthSIDE Glen]

Sorry Glen, I should have been more clear. I've only noticed while monitoring my own voice live, not on playback. Thanx for your last post, combined Mixit's info, that pretty much explains it.

No need to be sorry, Rams. As long as you got down now, and it sound like you probably do. All is well

P.S. And NO, I really don't want to get into the whole phase/polarity thing again. The last time RobD and I churned through all that was honestly exhausting. I'm just going to leave it as:

Phase inversion: V2 = -V1 + Vr

Polarity inversion: V2 = -V1

G.

[EDIT]P.S. Thanks for the edumacation, mixsit. I've not considerd that before. It just goes to show ya, it's always somethin'. "You must spread some reputation around..."

 

[dualflip]

True only if there is no DC offset in the signal. Granted, 99 times out of a hundred, there won't be offset (unless you're going through a stock laptop soundcard, in which case all bets are off

Well yes, you are aplying it to electronics, or digital recording which is correct, although i as aproaching it more as a physics phenomena