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absolute phase - Page 2

post #16 of 109
10/12/04 at 7:32pm
Thread Starter 
quotes
Qualia looks like a possibility because they appear to be the same dia...not sure again.

Same diameter pins however the connector housing is polarized and won't
go in the other way.



Two pins to each channel - one is live and the other is "return" right? Both returns from left and right merge into the ground ??

Yes. The return from each channel is soldered together at the jack.


Jeffemeister is right, i have a krell preamp, forgot all about the phase button.
Time to do some serious listening.

On some music with speakers i could definitely tell that there was a difference.
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post #17 of 109
10/12/04 at 8:23pm
I can tell the difference in Subwoofers...makes a big difference.

Can someone comment on the relevance of the Phase switch on one of the Grado headphones? HP2 ??
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post #18 of 109
10/12/04 at 8:23pm
Quote:
Originally Posted by john_jcb
This must be a real hoot sitting back and listening to the responses. If it really made a difference it seems to me that it would have been sorted out long ago and one way would be accepted and the other discredited. Smells more like a red herring to me.

Probably people didnt notice at all...or nobody bothered...

I dont know...im in for the learning process.
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post #19 of 109
10/12/04 at 8:36pm
deleted
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post #20 of 109
10/12/04 at 8:41pm
While relative phase is easy to pick up, absolute phase is much more difficult. It varies from disc to disc. Even if you have a phase inverting pre-amp, many times the DAC or the phone pre-amp also reverses phase. With a speaker system its easy to take care of it if you only have one item that inverts phase by switching positive to negative at the speakers. But if you have lets say a pre-amp that reverses phase and a cd player that does not, and a phono pre-amp that does, you would be switching the speaker leads every time you change source. I can't be bothered. And since you don't know the phase of the recording you guessing anyway. I've owned several pre-amps that had a phase reversal switch. Last one was the Sonic Frontier Line 2. I couldn't tell the difference between the two positions. But it was useful to take care problem caused by multiple sources with different final phase.
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post #21 of 109
10/12/04 at 9:21pm
It would be interesting to hear from Ray Samuels and Mikhail about their design philosophy and what they think of absolute phase.

Kevin may I infer that your amp designs do not invert phase?

Shucks now along with tube rolling, cable rolling, and power cord rolling we’ll have to check for phase inversions.

I remember a few people mentioning using the phase switches on the Grado HP1’s and believing some recordings sounding better but in general it seemed the phase switches were more of a novelty than a must have.


Mitch
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post #22 of 109
10/12/04 at 9:52pm

out of phase?

Quote:
Originally Posted by kevin gilmore
quotes
On some music with speakers i could definitely tell that there was a difference.
Is reverse phase the same as "out of phase"?

I have an old stereophille test CD that has its 3rd track called "Channel Phasing with the Audio Anarchist & Ralph the Christmas Dog". When channels are in phase you hear the dog clearly positioned in between the speakers. Out of phase it's postion cannot be determined. My speakers are el-cheapo Athena AS-B2, but still this demo works quite well.

With HD-280 phones I can't really tell where the dog is, although "out of phase" sounds a bit less "natural". Still phase doesn't seem to matter on these cans because they have poor soundstage to begin with.

Is this what you're guys are talking about, or is it something else...

Edit: on more careful reading, obviously not the same. You guys are worried about absolute phase of both channels. "out of phase" is when channels have different phase due to improper cabling. Right?
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post #23 of 109
10/12/04 at 9:58pm
Of course, the absolute phase of the equipment doesn't matter all that much if the source is recorded with the wrong absolute phase (hence the phase switches on the HP-1). While at times I thought I heard differences using the HP-1 phase switches, I'm not convinced of it. If I did hear anything, though, I'd bet that absolute phase was random on many CDs, from track to track. Sometimes correct, sometimes inverted. As I said, I'm not convinced I truly heard anything.
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post #24 of 109
10/12/04 at 10:08pm
Gaboo wrote:
Quote:
Is reverse phase the same as "out of phase"?
No ... "out of phase" is when only one lead is reversed. Usually results in reduced bass and unfocused sound.
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post #25 of 109
10/12/04 at 10:31pm
Ok, now I understand the problem: on an impulse signal the speaker cone would have wrong initial movement, e.g. instead of pushing air towards you, they'd pull. I can also see how this would be more noticeable (if at all) on low frequencies and transients.
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post #26 of 109
10/12/04 at 10:54pm

Tried it digitally

I opened a track in audacity and inverted (in audacity speak) a few selections. On some selections I didn't bother to find zero crossings, so could hear pops at the phase change points. On other chunks I did find zero crossing first (this is automated in audacity btw), so the transitions were seamless.

Bottom line: I cannot distinguish between normal and reverse phase even when I can tell where crossing point is. Let alone detect a zero crossing inversion point... I tried both with speakers and HD-280 cans, which have pretty good low bass. Nada, zilch. Oh, and the track was from the only hip-hop album I have. I figured it had the punchiest bass, i.e. low freq transients, so it should be noticeable. Not in my system.
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post #27 of 109
10/12/04 at 11:26pm
Kevin may I infer that your amp designs do not invert phase?
Quote:
Originally Posted by kevin gilmore
Amplifiers known not to invert phase
My amplifiers (both tube and solid state)
Not much need to "infer" anything!
CPW
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post #28 of 109
10/12/04 at 11:49pm
I'm skeptical that absolute phase makes any difference at all. For it to make a difference in the ear, you'd have to believe that the cilia waving in the inner ear are both directional and can detect whether the very leading edge (and only the leading edge) of an incoming wave is pushing or pulling. You'd also have to believe that after sound has bounced around the curves of the cochlea before reaching the appropriate cilia, the very leading edge of each incoming wave has not had its absolute phase become diffuse. All very unlikely.

Perhaps it makes a difference at the transducer, since there are physical consequences to the air pressure either increasing or decreasing that might affect the transient response. Any effect would likely be less noticeable with headphones. It could also make a difference in the body's physical response to lower bass. Again, not a serious issue with headphones.
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post #29 of 109
10/13/04 at 12:07am

The Emmeline Amps..

All the Emmeline line of headphone amps, including " THE STEALTH" as a headphone amp, do not invert the phase.
Ray samuels


Quote:
Originally Posted by kevin gilmore
This ought to spark some lively debate...

So i was looking thru a few OTL tube amp schematics and i noticed
that virtually every tube headphone amplifier inverts phase. A quick
glance at a number of solid state units and none of them invert phase.

So that got me to thinking whether or not absolute phase really
makes a difference. Certainly many of the record companies go thru
great effort to maintain correct phase, especially on classical performances
so there must actually be something to this. The first high end grado
headphones had phase switches.

So when comparing a solid state and a tube amp at the same time, some
of the differences you hear may also be phase related.

Amplifiers known to invert phase

Ray Samuels Stealth
Singlepower (all models)
Woo Audio
Eddie Current
Wheatfield HA2
Rudistor RP4

Amplifiers known not to invert phase

Ray Samuels SR-71 (and presumably all his solid state models)
My amplifiers (both tube and solid state)
PPA
melos (balanced input models could actually be wired either way)
cmoy, meta42 et all...

So all you people out there with tube amps and sennheiser headphones,
flip those connectors around and see if you can hear the difference.
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post #30 of 109
10/13/04 at 12:44am
Quote:
Originally Posted by Ray Samuels
All the Emmeline line of headphone amps, including " THE STEALTH" as a headphone amp, do not invert the phase.
Ray samuels

Ray - do you think inverted phase will be an audible quantity? I am still not 100% clear how this works...from my understanding it basically works like a "delay" by one cycle...not a big deal but I am known to make big errors in understanding and hence I am not optimistic that my observation is valid...

This is a DELAY :



This is a PHASE INVERSION :



I think I understand now...

There are two options :-

1 - OUT of PHASE with respect to TIME
2 - OUT of PHASE with respect to AMPLITUDE

We are obviously interested in the second option
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