M. Gregg, I have a feeling that you actually hear differences in audio parts, like many of us do. Measuring it is usually more difficult, but even WHEN it is measured, nobody here wants to believe it. Too bad, the differences still exist, and are a major key to quality audio electronics. Even the BEST topologies, that measure well with conventional audio test equipment, can still sound lousy to people like you or me. I use this ability to improve my designs. Works for me!
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Just another laugh,
I will shut up because it goes on and on..
The directionality seems to be optional, cost adder?
The directionality seems to be optional, cost adder?
Of course, think of all the effort to train the electrons. Or maybe they just select them and then mark them.
Where we disagree is that my OPINION is that directivity is possible under some conditions. Not easy to do and can be condidered a defect, but just might be possible.
You still have not posted links to any papers that you have alluded to on this low current conductivity hypothesis. Non-ohmic junctions would be pathological for resistors and I don't know of any physics for ohmic metal to metal junctions to have a prefered direction.
This paper is OK and not very well translated but they did CLT-1 and second harmonic tests, of course they concluded the seconds were rectification without solid proof.
Never heard of this before even when working on some serious analogue boards....
Given how many of "us" refuse to do proper bias-controlled listening tests...
Some of us wonder what "actually" really means.
False claim. I'm here and I believe that measured differences exist.
Please see former comments about bias and listening tests. Some of us are in denial about bias, others simply include it in our judgements of sound quality.
If it works so well, why the angst about proper bias controlled listening tests?
I think you meant ' if I knew a resistor had significant dissipation I wouldn't do something boneheaded with the traces'. Even then not sure how one end hot and one cold would cause magical effects esp if the cold end was on a ground plane.
Orientation of course matters if resistors need to track each other from a tempco perspective, but that's university stuff.
the disimilar metals between the copper traces and the resistor terminations will have a thermo electric effect.
If each junction of one metal to the next are exactly replicated on the other side and are at exactly the same temperature then the two voltages cancel.
If every metal to metal junction is done to maintain same temperature on the two sides then all the thermo electric voltages cancel.
One method of helping that is to orient the resistor across any cooling airflow, so that both ends receive the same cooling and thus end up at the same temperature.
A convection cooled PCB standing up in the nearly still airstream should have all the resistors sitting horizontally to minimise the differential temperature effects.
Vertical resistors and/or resistors that are artificially heated by another heat source may give rise to unwanted thermo electric voltage that could screw up performance.
A through hole resistor could have the following metal sequence from leaving the PCB to returning to the PCB
copper, solder, tin, copper alloy, brass, Nichr, brass, copper alloy, tin, solder, copper.
That is a lot of metal to metal junctions, each of which could have a different voltage.
If each junction of one metal to the next are exactly replicated on the other side and are at exactly the same temperature then the two voltages cancel.
If every metal to metal junction is done to maintain same temperature on the two sides then all the thermo electric voltages cancel.
One method of helping that is to orient the resistor across any cooling airflow, so that both ends receive the same cooling and thus end up at the same temperature.
A convection cooled PCB standing up in the nearly still airstream should have all the resistors sitting horizontally to minimise the differential temperature effects.
Vertical resistors and/or resistors that are artificially heated by another heat source may give rise to unwanted thermo electric voltage that could screw up performance.
A through hole resistor could have the following metal sequence from leaving the PCB to returning to the PCB
copper, solder, tin, copper alloy, brass, Nichr, brass, copper alloy, tin, solder, copper.
That is a lot of metal to metal junctions, each of which could have a different voltage.
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Not sure who you are answering here but 'the two voltages cancel' is possibly the physics fail of the week!
if you have a copper to nichro junction and a matching nichro to copper junction and both are at the same temperature, then the voltage generated across the two junctions are of equal value and opposite polarity, i.e. they cancel. The net thermo electric effect is nil.
Although you did not recognise it, I was answering yourself
Although you did not recognise it, I was answering yourself
Not magical !
Agree.
Two batteries, same voltage, opposite polarity, in series, cancel each other.
No matter what the voltage generating method is: chemical/thermal/piezo/tribo/photo voltaic.
Feel free to add other methods I left out.
EDIT: since people tend to nitpick on these 1000 post threads (that's one reason why they grow so long, by the way) ,let me clear that I meant *voltages* cancel ... internal impedances add up of course.
Other important parameters which also add up instead of compensating: price/weight/dissipation/heat output/PCB real estate/etc. etc. etc.
Two batteries, same voltage, opposite polarity, in series, cancel each other.
No matter what the voltage generating method is: chemical/thermal/piezo/tribo/photo voltaic.
Feel free to add other methods I left out.
EDIT: since people tend to nitpick on these 1000 post threads (that's one reason why they grow so long, by the way) ,let me clear that I meant *voltages* cancel ... internal impedances add up of course.
Other important parameters which also add up instead of compensating: price/weight/dissipation/heat output/PCB real estate/etc. etc. etc.
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If you have a leaded resistor you have a significant thermal mass compared to the trace it connects to. In your first post the nichrome connects to brass, suddenly its copper. Which is it?
As Scott pointed out some posts back the Seebeck effect probably explains most things. I assume you were just repeating that with added confusion? If so I agree with you and would assume you agreed with my first comment of the day ref boneheaded layout. It's still not magic tho and in audio you would have to try quite hard to make it audible as things tend to stay at a fairly constant temperature so there are just a few DC offsets to deal with.
As Scott pointed out some posts back the Seebeck effect probably explains most things. I assume you were just repeating that with added confusion? If so I agree with you and would assume you agreed with my first comment of the day ref boneheaded layout. It's still not magic tho and in audio you would have to try quite hard to make it audible as things tend to stay at a fairly constant temperature so there are just a few DC offsets to deal with.
At speaker levels 1uV/C thermal EMF is the least of your worries. Unless you are in marketing
Why don't you just measure a few resistors with a 5.5 or 6.5 digit DMM? I did, and found a small, but reproducible difference of the order of a few ohms for 22k to 100k resistors measured in both directions.
One explanation that made physical sense is that there's a weak metal-semiconductor junction at each end-cap, shunted with a dominant ohmic junction. Added to that would be the thermoelectric effects mentioned by Scott. There's no reason that all these are exactly identical and cancel out perfectly at both end-caps. If there's slightly more oxidation at one end-cap, it may show a stronger metal-semiconductor junction, or a slightly different thermoelectric voltage.
I generally find that noble-metal terminations like Silver-Palladium measure and sound better than compositions that contain Steel, Nickel, etc. but YMMV. This would correlate well with the chemistry - there's likely to be less oxide formation on the noble-metal terminations during deposition, plating, bonding, etc.
If you turn a resistor round though it would be identical...
As to dissipation, when doing relex (MTBF figures) I or the irrelevant engineer will add an attribute to each resistor with the working voltage across it, this is spat out to a nice excel spread sheet (that an engineer threw together) with other relevant data from the parts library that then gives a pretty coloured indication of rated power used, 50% is red (no go) 25% amber and below 25% green.
Of course most (if not all) sensitive analogue stuff I tend to work on uses SMD components because of the many benefits (thermal control being but one, smaller loop areas being another important one). Also all calculations are done at the extreme operating temperatures of the product. Being able to create a difference on a PTH resistor due to layout would take some doing IMO. There is all sorts of stuff that is done routinely in layout these days, but when I look at a lot of audio it just looks like the PTH boards I was doing when I started, nothing new in a lot of cases and anything new such as SMD (ha ha) is treated with suspicion or like ferrites just sounds bad because a few say so.....
http://www.tek.com/sites/tek.com/files/media/document/resources/1132_Low_Voltage_AN.pdf
http://wings.buffalo.edu/academic/department/eng/mae/cmrl/Thermoelectric behavior of soldier.pdf
How relevant do I think this would be to normal audio.... I don't know, it feels like trying to count the angels on the head of a pin.....
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