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Old 28th July 2009, 10:27 PM   #541
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Quote:
Originally posted by 1audio


Sometimes you make do with what you have-

Start out with two oscillators, a very stable low distortion low frequency oscillator and a modulatable high frequency oscillator.

Run the lf oscillator a low level through the chain into a sensitive phase meter. Mix into the input the HF oscillator pushing the system to close to its power limits. Cycle the HF oscillator at various rates consistent with the thermal time constants in question. Pass the output through the LPF and see the effect on the phase meter comparing the input phase to the output phase.

I have read but can't cite references that the relative phase of a composite signal are not audible, however if the phase relationship is changed the change is audible. I don't know if there is any data on this.
It would work;

but what I had in mind, to make 2 very clean very stable HF oscillators with LF difference between their frequencies, run them both equally mixed, filter out them on output and see how big is their product of inter-modulation, and how big are phase differences when level of input signals changed slower than a thermal time constant.

One more option is (if an intermodulation is too low) to rectify an output precisely to get it's elvelope then filter, and all the same.

The third option is, to use the 2'nd one, but with a synchronous demodulator. Phase shifts would be easy detectable in such case.
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Old 29th July 2009, 01:28 AM   #542
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I hate to say it, but: SO WHAT?
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Old 29th July 2009, 01:30 AM   #543
FrankWW is online now FrankWW  Canada
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Quote:
I have read but can't cite references that the relative phase of a composite signal are not audible, however if the phase relationship is changed the change is audible. I don't know if there is any data on this.
This might be of interest:

An introduction to the psychology of hearing
By Brian C. J. Moore

http://books.google.com/books?id=tkb...esult&resnum=1


I'm loathe to quote very much of this, because it's copyright and I'm not sure this is a legal download in the US or even possible to download there. Its certainly not possible to copy it.

Moore is writing about the psychoacoustics of loudspeakers and says experiments indicate we can discriminate between transient sounds differing only in the relative phases of the components - durations as small as 2 - 3 ms.

Also, (I'm typing from my copy):

Quote:
Changes in the relative phases of components are much more noticeable when these components are close together in frequency than when they are widely separated (see Chapt 3, Sec 4D), so phase changes which occur abruptly as a function of frequency have a larger subjective effect than phase changes which occur gradually over a wide frequency range. Unfortunately, the former is the common situation..
And:

Quote:
Blauert and Laws (1978) investigated the audibility of phase distortion by taking a variety of complex sounds, including speech, music, noise and brief impulses, and delaying a group of frquency components with respect to the remainder. They found that the minimum detectable delay was about 400 microseconds when the frequencies delayed were in the range of 1 - 4 kHz.
PP 345 -346

I can't recommend this book too much. Wonderful lots of references.

See also:

http://www.jstor.org/pss/3066509
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Old 29th July 2009, 01:53 AM   #544
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Frank;

subconscious mind can distinguish 10 microseconds, when conscious mind 10 miliseconds only.
How to prove?
2 snaps near the same ear VS 2 snaps near different ears.

That's why I absolutely don't care of conscious judgments of experts, but pay very close attention to emotions caused by sounds in persons who are far from music. Why? Because musicians and others who often deal with music have well trained musical imagination so they easily delete distortions, add missing information, and hear in imagination another instruments than are reproduced.
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Old 29th July 2009, 01:53 AM   #545
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Quote:
Originally posted by john curl
I hate to say it, but: SO WHAT?
John, I'm really sorry you have been having problems. I have several relatives in the same situation and my father went years with these issues. We always think things will go on and on, no worries.
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Old 29th July 2009, 01:55 AM   #546
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Quote:
Originally posted by scott wurcer


John, I'm really sorry you have been having problems. I have several relatives in the same situation and my father went years with these issues. We always think things will go on and on, no worries.
My father in law wears black glasses after each shot. It is pain to see him...

Get well John, we need you! We need you exactly who you are: rude, nice, don't matter. However, it is better to see you smiling...

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Old 29th July 2009, 01:56 AM   #547
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Wavebourn,

I like what you say! It is much closer to reality than are isolated lab produced experiments. They too often become ends in themselves rather than a means to an end....there is a point where instinct and intuition aka as an act of faith must play a part.
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Old 29th July 2009, 02:01 AM   #548
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Quote:
Originally posted by brianco
Wavebourn,

I like what you say! It is much closer to reality than are isolated lab produced experiments. They too often become ends in themselves rather than a means to an end....there is a point where instinct and intuition aka as an act of faith must play a part.
Heh-heh...




By the way, what I said that info about 10 mili- and micro- seconds was proved in the lab by (AFIAIR) the same Blauert that Frank mentioned.

...and 30 years after people continue arguing about phase modulations and listening tests.

You are absolutely right: results of experiments die in files.

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Old 29th July 2009, 03:39 AM   #549
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Please stick to the technical subjects, engineers. I can't add much to the technical xxxxx that has been put forth in the last few days. That is my greatest frustration.
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Old 29th July 2009, 04:00 AM   #550
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If someone wants to measure the dynamic diode changes with temperature in an output transistor, for example, then just get a device with added diode on the substrate, and measure it directly. This could be done with input stages too.
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