[jcoat007]

I have a button on my pre-amp labled "phase".  I have never used it.  I was playing some vinyl at very high SPL's and when I hit the button it seemed to really clean things up.  

What does this do?

[PhilNYC]

It inverts the phase of the audio signal in your preamp.  Most tubed preamps invert the signal phase.  Without a phase switch, you would have to reverse the positive/negatives when connecting your amp to your speakers (ie. connect the "+" from your amp to the "-" on your speaker, and vice versa) to get the correct signal to your speakers.  But with a phase switch, you can set up your cables as you normally would and invert the phase on your preamp.

[jcoat007]

Thanks for the quick reply.  How can I confirm that my pre-amp is inverting the phase?  It's a Sonic Frontiers Line-2.

[PhilNYC]

I think I've read somewhere that the SF L-2 does invert phase, but I don't remember where.  It should probably tell you in the owner's manual.

The fact that you like the sound better with the phase switch engaged probably is a good indicator that it was inverted before.  And in any case, it only really matters whether you like it better or not...  

[jcoat007]

If you go to this link

http://www.anthemav.com/OldSitev1/frames/manualsfr.html

and then go to the Line Series Preamplifiers owners manual.  At the bottom left colum of page 4 you will see the explanation for the Phase Button.  It seems to indicate that it is based on the recording.  

I know I am confused, but as you said, "...it only really matters whether you like it better or not..."

Thanks

Steve

[PhilNYC]

Steve,

It's true that some recordings are pressed with phase inverted (either intentionally or accidentally).  But it's also possible for a system to invert phase.  Basically, if a system inverts phase, then it reverses the phase of every recording it plays back.  If a system is correct-phase, then it will play the recording in whatever phase it was pressed.

It may sound confusing, but it's not really.  And as said, since you have the phase switch, you can basically choose whichever makes you happier...!  

[andyr]

To be slightly more precise, what we are talking about here is "correct absolute polarity" vs. "inverted absolute polarity".  Clark Johnsen wrote a seminal book about this called "The Wood Effect" (if you want to get hold of a copy, email Clark at "Positive Feedback").

Remember, first, that it's not just your preamp which might be inverting polarity - it could be happening at any active gain stage in your sound chain.  The net result of the sound chain is, as Phil pointed out, either your system (as a holistic whole) inverts polarity or it doesn't.

However, be aware that one front-end component might invert polarity (like a phono stage) while another does not (say, a CDP).  So having a switch on your pre-amp to counter this is a real godsend!!

However, then there's the matter of the source recording.  One might think that competent sound engineers would always have taken the effort to make sure all their mikes were set up with correct polarity (to take a simple example, when a singer blows into the mike, the diaphragm should deflect backwards).

However, they all didn't in the old days and they may still not.  If all the mikes are set with the same polarity then your "phase switch" can instantly convert one polarity to the other but if some mikes are set "correctly" and others invert, the listener has a problem!  Again, at least those lucky people with a phase switch can try both settings and decide which one they like best!

I certainly wish I had a polarity reversal switch on my pre-amp!!

Regards,

Andy

[jcoat007]

Here is a link to the article in Positive Feedback by Clark Johnsen.  This whole issue is a mess and, as usual, ,it comes to down to using your ears to hear it.  

http://www.positive-feedback.com/Issue1/cjwoodeffect.htm

[JasonW]

Assuming the recording is done with the correct polarity, differences between inverted and non inverted polarity can be described as:  Inverted polarity increases the depth of the soundstage but lacks a degree of believability that the non-inverted has (Think w/ inverted polarity it's almost like the singer has his back to you)  With non inverted polarity, the soundstage is not as deep, but the sound is more believable compared to inverted.  Hearing these differences depend on how resolving a given system is.  I can fairly easily hear the difference between inverted and non inverted polarity when a/b on my system.

Jason

[Tonto Yoder]

FWIW, the Silent Running Audio site lists an absolute polarity chart by record label,  suggesting certain labels invert  phase all the time while others don't.

http://www.silentrunningaudio.com/AbsolutePhaseChart.PDF

I wonder about such a broad brush statement,  but the important thing is that absolute phase varies from recording to recording, so you have to listen each time or mark your CD's/LP's as to preferred setting.

There was an earlier thread

[hifitommy]

absolute polarity is a true issue.  the best implementation i can think of is a remote polarity switch.  adcom has that on some of their CDPs.  i was auditioning speakers in a shop and noticed the polarity button.  when i pushed it, the difference was surprising.  

that cd was ending up at my ears in reverse phase until i hit the switch.  whether your equip is in or out of phase depends on whether there are an even or odd number of gain stages between you and the signal.  if you can determine this, you can change it by changing the electrical phase of both of your loudspeakers (unless theyre active-self amplified that is).  

an even number of gain stages would result in correct absolute phase-theoretically.  as mentioned by others, some recordings are oop, and even some instruments or voices within a recording as well.  not much you can do about that.


so, i wish for remotely controlled abs phase, and vta on the tonearm too.

[Tonto Yoder]

Has anyone tried the phase switch with Patricia Barber's "Cafe Blue"??
I agree with Bob Crump's post on Audio Asylum that Barber's voice is recorded out of phase with her band.  A phase switch would make either her voice sound focused OR the instrumentation, but supposedly not both.

Much as I like this CD musically, I've never understood why it became an audiophile favorite.

[andyr]

...so, i wish for remotely controlled abs phase, and vta on the tonearm too.
 ...

Wow, remote VTA ... ya don't ask for much, hifitommy!

Would you settle for second best ... the Graham 2.2 lets you adjust VTA on the fly but you need a mate sitting in the listening chair, listening, while you focus on turning the micrometer wheel smoothly!

Regards,

Andy

[hifitommy]

SEND me one.   ;^)

[orthobiz]

I believe there is a phase test on the Rives Audio CD.

biz

[PhilNYC]

The phase test on the Rives CD tests if your left/right channels are in phase...it doesn't "test" for absolute polarity...

[andyr]

Be aware that Mr Rod Elliott - that fantastic fellow from Downunder - has just produced a "Polarity Inversion" circuit ... Project #107 at www.sound.au.com

At laaaast ....

Regards,

Andy

[orthobiz]

Phil,

But if the Rives CD helps test phase, wouldn't that secondarily allow you to know if your polarity was right?

biz

[ctviggen]

I have a set of Stereophile CDs that has a song with both correct phase and incorrect phase.  (I've not listened to it as of yet, though, because even they don't know which is which.)  Phase per speaker is different than absolute phase (on both speakers).  My Avia DVD has phase testing for all channels of a 5-channel system, but they compare two speakers at a time.

[orthobiz]

Does all of this mean that simply switching the speaker wire doesn't necessarily make the phase correct?

biz