Resistor Directionality and testing

[MRehorst]

Originally posted by Peter Daniel
Here's the link: http://www.diyaudio.com/forums/showt...835#post123835 and the pic of a test setup.

I can see a number of problems this set-up that I think would make it a very unreliable way to check resistor "directivity" or any other aspect of component "sound".

This unshielded arrangement is going to be prone to all sorts of radiation and noise pickup. There's a good chance that such noise will mask any effect of component "directionality", if any exists.

Then there's the contact method. Just relying on the spring force the leads provide is an extremely poor way to make contact with the part. Every time you move it (or some sound in the room vibrates it) the characteristics of the contacts will change. The plating on the component leads and the plating on the connectors may be different materials forming point contact diodes. Dirt or crud on either the leads or the connectors will interfere with the connection.

I think a better test would be to build two identical amplifiers with all the components matched and installed with the same "polarity". Build it in a properly shielded enclosure and use a quiet power supply. Feed the same signal into both amps, then observe the difference between the outputs. This will be the baseline. Next reverse the one component in question, and observe the difference between the outputs. I would use a simple amplifier such as a very low noise, low distortion, wide bandwidth op-amp, one with multiple amps on a single chip to ensure that they are matched. The outputs of those amps would drive a similarly low noise, wide band, low distortion instrumentation amplifier. Observation would be done in both frequency (spectrum analyzer, noise analyzer, etc.) and time domain (oscilloscope, freq selective voltmeter, etc.). Several different test signals, steady and dynamic, could be devised and applied to the circuit to check specific aspects of the behaviour.

Such a test set up would require a lot of time, money and effort. Not many people have the access to such equipment. Even fewer of those who do would be interested in performing such a test.

Oh well...

MR

[Peter Daniel]

Originally posted by MRehorst
What you think is a difference between resistors may just be a difference between poor contact with the connectors. Radiation is not steady state, so when performing different tests at different times, one may be subject to radiation that the other is not.

If this differences are consistant in subsequent testing for certain brands of resistors, I'm ruling out poor contacts factor. I made the tests in a period of 20 minutes, so I ruled out changing conditions as well. Why don't you try it yourself and agree with me?

I did quite a few tests of this type and can assure you that quality of the contact is not a problem here. Controling vibrations ibrations is a totaly different issue.

[Steve Eddy]

Originally posted by hifiZen
C'mon Pete! I know you can do a more scientific test than this! Let's see those construction skills shine!

Well, as long as he's doing the testing (i.e. listening) sighted, it's really not much of a scientific test to begin with, construction skills notwithstanding.

se

[Peter Daniel]

Originally posted by Steve Eddy



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.

Whatever it was (true or not), I am glad that I could decide for myself, which way to put those resistors in a circuit and that the last amount of doubt is gone. Now, both my conscious and subconscious mind is happy.

[mrfeedback]

Steve,

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.

Well, yeah this is what we are on about.
Do you find any subjective differing directional results ?.
If you do, then there must be a physical reason, yeah ?.

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.

I meant changing polarity of input and output connections together in order conserve throughput polarity, but invert wire and transformer core polarity.
I do use my DPDT transformer arrangement so that I can easily select AP at my speakers, but that was not my question.
BTW - are you saying that you cannot hear AP ?.

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.

These differences were not subtle.
Go and read the thread that Frank refers to above and you will be clearer on what we mean.

Coming from someone who is wholly uncomfortable with the notion that they're a mere mortal human being, this comment is not suprising.

Double blind testing is typically worth less than a pinch of you know what, because of unfamiliarity with system variables - A/B testing blind or not is perfectly valid on a very familiar home system.

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.

I am perfectly concious of what my ears communicate, and I am perfectly familiar with interpreting this information under all sorts of conditions.
How exactly can your mind be sub-concious ?.

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?

Fine fair enough point.
In my younger years I read the brocures, and believed the spiels to be true.
When the salesman plugged in say, 'Monster cables', and said "Hear that better bass ?" etc, upon that power of suggestion, I did.
On subsequent learning, and far greater experience, I now do not pay the merest heed to such suggestion.
In my formative years, I did indeed perform experiments, and automatically considered them to be beneficial.
In later experimenting, I have learned that one can make very fine audible differences, but these are not always beneficial fine differences, especially with long term listening.
I am now well enough practised in this, that I find that I have a long term listenability/enjoyability handle on a new sound in about 5 seconds, and that these impressions prove to be accurate longer term.

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.

I thought that you were asserting that the claims of C37 and Tubolator cannot be true, or indeed possible ?.

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.

I do not swallow weird claims either, but I do studty the claims, reviews and information given, in order to sort the wheat from the chaff.
Within my experience, I fully expect that C37 and Tubolator do affect/effect system sound, however based on my experience, I am not sure that the effect is particularly significant, nor entirely likeable - this requires personal experience of these products, and that I do not have, and my soloution is quite different.

Eric.

[MRehorst]

Originally posted by Peter Daniel
It may surprise some of you, but I'll always choose convenience over reliability.

This supposed to be only a temporary and easy introduction to resistors comparison tests. I'm not claiming that this is a best way to do it, but if someone is reluctant to try those tests because of complexity of a setup, this should show a simple way to do it. If you try my method and will find that there is something to the differences presented, by no means go for more elaborate testing and use solder joints and all the rest of "perfect sound forever" accessories. For me this was good enough.

My point was that your simple test method is NOT a way to do the test. It is like sticking the resistors in your ears to see what the "sound" difference is. When the contact is unreliable, and the device is unshielded, you don't know what you may or may not be hearing.

If you want to do such a simple test setup and use only ears to evaluate the result, then shield the thing (just put it in a grounded box), an connect the resistor or other part to be tested using some binding posts or nuts and bolts and use a torque wrench to tighten the nuts uniformly and repeatably.

Whether THAT is a valid test is still debatable, but at least it should lead to repeatable results with minimized "noise".

There is another issue to consider- do resistors sound the same when they have only ac signals across them? Does ac + dc cause different sound? Does dc polarity and level affect the sound?

If none of this matters, and the whole point of the exercise is to fool yourself into thinking that you have actually tested something and have some valid results then your test set up really is optimal.

MR

[Peter Daniel]

Originally posted by MRehorst
Let me put it into terms that will be more clear to the parties involved: if I were to claim that using a stick of spagetti I can drill holes through aluminum faster than a drill bit, and stuck to that argument no matter what anyone said, I would be laughed off these forums. If I said you have to try it to know, again people would laugh.

Your example here, may seem funny to you, but it only shows how exaggerated your attitude is, towards the whole issue. Although your avatar shows an attempt to have an open mind, this is not a way to achieve it.

[Steve Eddy]

Originally posted by Peter Daniel
Whatever it was (true or not), I am glad that I could decide for myself, which way to put those resistors in a circuit and that the last amount of doubt is gone. Now, both my conscious and subconscious mind is happy.

And that's fine with me. That's how I approach it as well. If I subjectively prefer something, I go with it, whether it's due to physics or psychology. Just that unlike mrfeedback, I don't automatically assume and subsequently claim that my subjective perceptions are the result of actual audible stimuli.

se

[UrSv]

Originally posted by MRehorst


-- snip --
I am a professional engineer with 20+ years of experience designing ICs and test circuits for them. I have spent thousands of hours in test labs with real test equipment devising methods and measuring characteristics of components. Over the years, companies have invested millions dollars based on the results of my lab work.

I have pointed out OBVIOUS flaws in the test set up, yet people keep denying they are flaws. It is like I am saying an apple is an apple and people keep insisting that it is an orange. Even my five year old son is more reasonable than this.

If the test method is bad, the results are meaningless garbage. There is no rational way to argue against this.
-- snip --
MR

I will have to agree with Peter on his response. I think this is the problem. I see this problem almost every day with engineers and I am one myself. It is so easy to believe that for a test to have any value it needs to be 100 % controlled, measurable and undisputable in every way. Not so.

I also have 20 years of experience in testing and devicing test methods. I, however, have absolutely no problem with the set-up when the intention is a quick test for the claimed differences. Sure the set-up is not "scientific", flawless or even close to perfect but that does not mean that it is completely useless. I don't argue the fact that there are OBVIOUS flaws in the test set-up but any flaw does not automatically disqualify all results from a test. The concept of repeatability also helps in the value of the results in this case.