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Absolute phase
Absolute phase
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Old 15th December 2005, 08:45 AM   #1
cs is offline cs  United Kingdom
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Default Absolute phase

What are people's views on preserving the absolute phase of a system ? Is it audible ?

My current amplifier project uses an inverting, shunt feedback configuration, as this gives best performance. But should I correct for the inversion, either using an inverting input buffer, or by reversing the speaker connections ?
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Old 15th December 2005, 08:56 AM   #2
dhaen is offline dhaen  Europe
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This crops up from time to time. Here's the last thread:
Audibility of absolute phase
There are many more references you can search for.
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Old 15th December 2005, 09:19 AM   #3
lineup is offline lineup  Sweden
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Another question:

Is there any difference using these two setups in stereo

1. Two Inverting amplifiers with exchanged LSP connections
2. Two Non-inverting amplifiers with normal plus/minus connections

And what will happen if
Using alt 1) for left channel and alt 2) for right channel
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Old 15th December 2005, 01:16 PM   #4
Jay is offline Jay  Indonesia
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I think there's a thread where Nelson Pass suggested to "correct" the absolute phase. I haven't bothered myself trying to find out first hand whether it is audible or not but I had an experience in digital area...

There was a confusion in DSP/DAC chips about signal inversion, and I couldn't find reliable information so I setup 2 circuits, 1 with inverted signal. The difference was clearly audible (may be the unequal circuit played big role there). But what I didn't expect before was, I had no idea which one is the "correct" one. I had a guess (that the one with less dynamic is incorrect), but how can I be sure?
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Old 15th December 2005, 01:47 PM   #5
djk is offline djk
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"And what will happen if
Using alt 1) for left channel and alt 2) for right channel"

Can sound very bad at high drive levels. This is due to dynamic off-set of amplifier when handling asymetrical signals (music).

Carver (and others) tried this and then dropped.
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Old 17th December 2005, 01:52 PM   #6
AndrewT is offline AndrewT  Scotland
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Hi Djk,
I don't understand your logic for arriving at your answer.

The two options require two different amplifiers.
An inverting amplifier on left channel with the loudspeaker connections reversed.
A non inverting amplifier on the right channel with conventional connections to the loudspeaker.

Both these arrangements will give correct absolute phase at the audio output (if the input signal is correctly phased).

Dynamic offset and asymetric signal handling can't interact between two different amplifiers,

Please explain further.
regards Andrew T.
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Old 17th December 2005, 03:28 PM   #7
GRollins is offline GRollins  United States
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It's audible, but subtle. Most people don't notice. Listen to the impact of bass drums, for instance--it's slightly more pronounced when the absolute phase is correct.
If your amp is phase-inverting, reverse the speaker hookups.
This is the one thing that saved Douglas Self from being a complete fool in my eyes. He went on and on and on about how people were delusional when they claimed that they could hear things, then was man enough to admit that he was wrong when it was proved that absolute phase was, in fact, audible. Never had I seen a hard core measurements-are-everything guy admit to being wrong. They inevitably ignore instances when they are proven wrong (audibility of passive components being another case--see Jung & Marsh) and keep right on ranting. I respect him for his admission of error.
In any event, it's a low-level phenomenon. It's not the kind of thing that you should loose sleep over. But, being as easy to correct as it is, why not fix it?

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Old 17th December 2005, 10:47 PM   #8
mastertech is offline mastertech  Australia
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Mr Rollins thanks, i dont understand yours or Mr self's explanation
of ab-phase being audible perhaps, if you could elaborate more
with some hard scientific evidence to back it, i would be more
convinced, i understand it like this it sounds good/better or
different, that makes it a subjective evaluation which is entirely
based on perception in other words if subjective evaluations had
a scientific basis there wouldnt be subjective and objective camps
i respect both you and self, but i think youre both alittle bit confused right now

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Old 18th December 2005, 01:42 AM   #9
chipco3434 is offline chipco3434  United States
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Get this guy an emergency shipment of periods! Mastertech, do you know about those little dots that end sentences?

Here, take some of mine................................
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Old 18th December 2005, 04:18 AM   #10
GRollins is offline GRollins  United States
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Personally, I'm rather amused that anyone would ever lump me into the same category as Doug Self.
It sounds as though mastertech has gotten himself lost in a philosophical conundrum.
Answer this, Grasshopper, and you will find the answer: How do we know anything at all?

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