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Old 18th February 2003, 01:55 AM   #11
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Default A Better Test Method ?....

I agree that resistors of differing values will likely behave slightly differently.
So I propose that a more valid test is to connect two suitable value resistors in series (or parallel), and reverse the direction of one or both resistors methodically, in order to detect audible directional differences.

One point worth mentioning here is that it seems that solder joints change according to the maximum level passed through them.
I find after blanket resoldering an amplifier stage, that on initial runup the sound if kept at low or medium levels can sound strangely 'wrong'.
If the amplifier is driven to momentary clip, the sound changes and remains different and stable thereafter.
I do not have a solid explanation for this effect, but I have proven it many times.

For the resistor direction test to be more valid, I feel that attention needs to be paid to this curious effect - ie run the level up to momentary clip and turn down, turn the sytem off and then back on before taking a proper listen for any sonic changes according to direction.

Eric / - The careful listener.
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Old 18th February 2003, 03:00 AM   #12
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Default Re: A Better Test Method ?....

Quote:
Originally posted by mrfeedback
One point worth mentioning here is that it seems that solder joints change according to the maximum level passed through them.
I find after blanket resoldering an amplifier stage, that on initial runup the sound if kept at low or medium levels can sound strangely 'wrong'.
If the amplifier is driven to momentary clip, the sound changes and remains different and stable thereafter.
I do not have a solid explanation for this effect, but I have proven it many times.
That indicates you could have either a bad solder joint or a defective switch/relay contact in the amp. I had a similar problem with an active crossover in my church's sound system. At powerup one of the output bands of the crossover would sound soft and kind of muted. If you gave it a hard hit of signal it would start working correctly, but typically the next time you powered it up the problem would be back. I resoldered all of the XLR connectors and the problem was eliminated. I have since seen this specific symptom mentioned by Ashly and Mackie in technical bulletins describing problems with defective solder joints in PCB mount connectors and ribbon cables.

Switch and relay contacts demonstrate this same behavior. Once current is flowing through a contact there is an electronic self cleaning action that prevents oxide build up. However once the current stops an oxide film begins to build. Small signals lack sufficient voltage to break down the surface film which is why gold flashed contacts are required for reliable use with small signal levels. Once the oxide film is broken, the electron flow in even small signals is enough to keep the contact clean, but the problem comes back when the system is powered down again for any length of time.

In addition to looking for a cold solder joint I would also check any switch or relay contacts in the signal path. The specs I've seen for small signal contacts specifies that they will no longer meet requirements for small signals if the small signal current rating (usually 20 to 40 mA) is exceeded. What happens is that these contacts are the typical silver contacts with a thin layer of gold flashing to prevent oxidation. If the small signal current rating is exceeded, even for an instant, the gold flashing is gone and it becomes a normal high level contact.

Phil
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Old 18th February 2003, 03:49 AM   #13
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Default Re: The Sun Don't Shine Out Of My Butt Either.

ACK! Who wrote this software? Hitting the Escape key wipes out EVERYTHING you've typed. *sigh* Oh well, here goes the second try.

Quote:
Originally posted by mrfeedback
Hey Steve,
Have you tried reversing the polarity of the input and output connections of your audio isolating transformers, in order to guage any difference ?.
Sure. But when I do stuff like that, I'm just looking to see if I have any particular subjective preference. Not to establish any sort of physical reality beyond my own subjective perceptions.

Quote:
As part of my test bench, I have a pair of audio isolating transformers too, except that I have a DPDT swith wired as a reversing switch in series with the primary.
In previous experiments, I have reversed the polarity of both primary and secondary connections, and detected an audible difference.
Well, if there's anything to the audibility of absolute acoustic polarity (see Clark Johnsen's book, The Wood Effect), then making such a switch in polarity could result in audible effects which have nothing to do with the directionality of conductors. You're changing compression to rarefication and vice versa.

Quote:
I have also made non-directional star-quad interconnects too, and these made a non-subtle audible difference.
Great. However there have been some number of others who have made the same claims of "non-subtle audible differences" only to mysteriously have their ability to discern those "non-subtle" differences evaporate the moment the identity of the cable they're listening to is withheld from them.

Quote:
As far as sighted VS non-sighted testing goes, your comment is not woth the bandwidth.
Coming from someone who is wholly uncomfortable with the notion that they're a mere mortal human being, this comment is not suprising.

Quote:
You really ought to realize by now that amongst us here, are listeners who are easily able to divorce expectation from any listening testing, and if you are unable to do so, then please understand that other listeners are - Ummmm, fellows like Peter, Bob, Frank, myself and others I have missed mentioning.
I realize that there are some number of people who believe they can wholly divorce their conscious mind from their subconscious mind. But so far, all we have are empty claims.

Quote:
The key is an open mind - indeed if you convince yourself beforehand that these such effects are not possible, well then as a matter of course you will never hear them - period.
Yet the converse is somehow not also true? If one cannot hear something which is actually audible simply because they believe it to not be possible, why cannot someone perceive a difference when no audible difference exist simply because they believe it is possible?

Quote:
You know the origin of the Universe is hitherto still unexplained.
So? This proves your claim how exactly?

Your arguments are souding more and more like the arguments of the charlatans featured on Penn & Teller's new program, ********!

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If you have a workable theory, then by all means share your wisdom with us.


I'm not the one making the empty claims of fact here. Nor do I have any particular desire to attempt to establish any of my subjective perceptions as any sort of physical reality.

Quote:
Eric / - open minded on most things, and intolerant of sarcasm and baseless naysayers.
Yet you expect others to unquestioningly swallow the baseless claims of "yaysayers." Hmmm...

And FYI, I'm not a "naysayer." I just don't swallow empty claims without question. It's called having an open mind but not one so open their brains slosh out onto the floor.

se
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Old 18th February 2003, 04:05 AM   #14
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This is a quote from another thread dealing with similar issues. I think it's not too far from the truth:

"It is not possible to talk about the ear/brain system that is hearing without taking into account 'us'
that is one cannot seperate our conciousness from what we hear. As a consequence we all hear things
differently and we are all quite poor at repeatably hearing a piece of music as identically the same each
time we hear it... Our emotional state has a significant bearing on how we perceive the sound of music
- and since music itself is an emotional state modifier - we have an inherently 'unstable' system. That
is a system in which repeatable results are very very difficult to acheive.

This is the reason that double blind testing is so unreliable an indicator for sound quality - the act of
taking part in a testing process changes the way we hear the music and hence how we score the
sound..."
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Old 18th February 2003, 05:41 AM   #15
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Quote:
Originally posted by Peter Daniel
This is a quote from another thread dealing with similar issues. I think it's not too far from the truth:
If nothing else, that quote only reinforces the fact that there's a significant amount of psychology involved in our subjective perception of sound.

However I see a couple of flaws in the argument.

<i><b>...that is one cannot seperate our conciousness from what we hear.</i></b>

More like we cannot separate our conscious mind from our subconscious mind.

<i><b>This is the reason that double blind testing is so unreliable an indicator for sound quality - the act of taking part in a testing process changes the way we hear the music and hence how we score the sound...</i></b>

First, I haven't been referring to blind testing with regard to determining sound quality or personal preference but rather the ability to simply discern a difference between two elements. Not whether one is better than the other.

And the process isn't really different. When you were sitting listening to various resistors connected in both directions using your impromptu test rig, you were listening just as intently and analytically as you would be during a blind test. The ONLY difference is that under blind conditions, you wouldn't know beforehand which resistor you were listening to or which direction it was in.

And if you were able to discern a difference under sighted conditions, then there's no reason you wouldn't be able to discern those same differences under blind conditions if the difference were truly audible.

se
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Old 18th February 2003, 06:38 AM   #16
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Default Re: Re: The Sun Don't Shine Out Of My Butt Either.

Quote:
Originally posted by Steve Eddy
ACK! Who wrote this software? Hitting the Escape key wipes out EVERYTHING you've typed. *sigh* Oh well, here goes the second try.
Muat be your PC, i can press escape with impunity...

dave
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Old 18th February 2003, 07:18 AM   #17
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Default Re: Re: Re: The Sun Don't Shine Out Of My Butt Either.

Quote:
Originally posted by planet10


Muat be your PC, i can press escape with impunity...
Think it's the browser (IE5.5). Tried with several different text entry forms (Google, etc.) and it does the same thing.

My apologies to whomever wrote this software.

se
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Old 18th February 2003, 01:07 PM   #18
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Default Feel The Bass....

So, how does one know that they have a sub-concious mind then ?.

Just a question.

Eric.
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Old 18th February 2003, 01:22 PM   #19
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For me it works this way. Let's have that I have a design at task at I don't really know how to go about it. I usually go down to my workshop late at night, look at all the bits and pieces and just contemplate what I want to achieve with it. Finally, around 2 or 3 am I go to bed. Usually, when I wake up in the morning, I have a solution. Isn't it nice?
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Old 18th February 2003, 02:07 PM   #20
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Default Observations, Not Theories.

Phil, solder joint problems are not included here - note that I said after 'blanket resolder'.
I am well familiar with noisey contact problems too, and this is not the sound that I speak of, and besides all pot and switch contacts get treated before this initial runup.

I suspect that the resoldereing process demagnetises residual fields in component leads, and clipping level current pulses cause a remagnetising of component leads, and a consequent bias in characteristics.
The solder joints themselves may be part of this equation also, especially if a magnetised component lead is contained within that joint.
This sonic change occurs only once after a blanket resolder, and happens when the amp is pushed to momentary overload.

Eric.
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