Top resistors

Maybe the law of averages should be applied. Multiple measurements would mean multiple touches which may provide multiple numbers. Of course all of this would have to occur in the same time frame and with the same physical circumstance. If the numbers recorded on average from end to end were different it would seem to me that there is validity in Larry's method. Tom

Not having experimented with resistor directionality; I have no opinion regarding validity. However: I can't help but notice; in every picture the tester has his fingers on the body of the resistor and not touching either lead. no doubt; it would have been expedient, to have removed himself/his body from the test completely. Testing capacitors for outer foil, has shown me how much influence a body can have regarding induced noise. Why would the impedences of the probes, ground wire, etc not remain constant? According to the script; he was testing for voltage/mV differences. If the results were repeatable, and mostly constant, between resistors of the same value; I'd see no reason to doubt the conclusions he's made.

this direction matter has been debated in other forum, I read it and I tried it, so the result suprised me too..
as the link I provided he test the resistor in different method (with osciloscope and mine with ear).
so why don't you guys try it yourself and write down your opinion after...

cheers :)

05-26-13: Rodman99999
Testing capacitors for outer foil, has shown me how much influence a body can have regarding induced noise.

Exactly! And my suspicion is that if he were not holding the resistor in his fingers, he would not have had enough signal to make a meaningful measurement.

Note this statement in the page he links to about the corresponding measurement for capacitors (for which his methodology seems to me to make more sense):

How to do the test with Oscilloscope? Simple by testing both leads, and give some “interference” outside the capacitor (touch by hand or put some electric field interference e.g. high voltage cable, etc). The side with higher noise, means the outer foil.

Regarding

Why would the impedences of the probes, ground wire, etc not remain constant?

They would remain constant, of course, but the impedance of the path between his fingers and the probe's ground would depend on where he was grasping the resistor, and on which end of the resistor the ground clip was connected to. Likewise for the impedance of the path between his fingers and the probe's tip.

Visualize the situation taken to its extreme: He grasps the resistor at one end (without touching the lead). Regardless of the resistor's directionality or lack thereof, it would certainly seem expectable that he would see something different on the scope depending on whether the probe's ground or tip were connected to that end.

If the results were repeatable, and mostly constant, between resistors of the same value; I'd see no reason to doubt the conclusions he's made.

If the measurement were repeated for a number of resistors of the same type and value, and if he grasped each of them at approximately the same position, and if he kept his body located and positioned similarly throughout all of the measurements, I'd expect the results to be reasonably consistent. However, I don't see how those results would say anything about the directional characteristics of the resistor. They would just say something about the net result of the interplay of the five factors I listed in my previous post.

Regarding my previous post, btw, upon re-reading it I realized that the following sentence is flawed. Consider it to be deleted from the post:

That conclusion would be true even if he managed to grasp the resistor exactly at its mid-point, due to the differences in AC leakage to the probe's ground and its tip.

Regards,
-- Al

Bruce Hofer (founder of Audio Precision) did a recent AES Convention lecture on many topics pertaining to low-THD circuit design, including parts quality in both capacitors and resistors. He was kind enough make the PowerPoint slides available for download in his May newsletter, which can be found here: http://www.ap.com/kb/list/2

You do have to register to have access, but there's a wealth of tips available from one of the true modern masters of analog audio design.