mach1 said:
Is that all there is to it, Is it just a matter of 'belief'? Is nobody anymore interested in finding out how much their belief matches the real world out there?
If NASA's engineers use certain procedures and mathematical frameworks to work out when to ignite the shuttle engine to land it safely, is that just a matter of 'belief'?
If two people come to different conclusions as to whether two amps sound different or not, is that just a matter of 'belief'?
I say NO! Some things match reality to a large extend, some don't. If you subcribe to a 'belief', you implicitly say that you don't give a hoot anyway.
Jan Didden
SY said:
Yes, agreed. Experiments. If they are done the Scientific Way. Meaning that you double check, double blind, try to find the weak spots in your own reasoning and clear them up. Etc.
An 'experiment' is not buying an expensive cap, plugging it in, turning on the system and shouting, hey that sounds great!
Jan
I'm far away from my field on this comment, but would also suggest learning to experiment with your mind. I don't mean drugs, but learning to recognize your biases and even change them to some extent- play devil's advocate. Suppress what you think you know. Take up a contrary position. Believe it. I'm still messing with the different conductors because if there's a chance of some missed property, I want to find it. An additional note on that ongoing test- when I thought I heard a difference, it was with the headphones connected directly to the amp outputs. Signals were at very low levels and SN ratio was probably pretty lousy. I added an output pad (1 ohm and 25 ohms) and got the levels up to something more reasonable. No detectable difference at that point. The differences I thought I heard between interconnects went away as well. My guess is that the lower resistance silver improved the grounding or otherwise reduced or changed the character of the noise a bit, and I reacted by thinking the music improved. Confirming that sort of thing by measurement becomes problematic- I can easily measure SN ratio, but I've no idea how the brain reacts to it. Thoughts?
The comment on mics is interesting because it suggests listener fatigue or some similar thing. I have to believe there are real differences between mics. I only have a Shure dynamic vocal mic, and an import large diaphragm condenser mic, but they seem very different in response. My test is ongoing for just that reason. Maybe I'll hear something I missed if I'm more relaxed. FWIW, some of my favorite test tracks are Joan Baez Diamonds and Rust from the UK import CD, or a transfer of same I made from vinyl. The opening notes have a squeak that should be just right, not to mention her voice, and there are some quiet and low frequency drums I find telling. Also, Pachelbel from an Archive CD (Reinhard Goebel) is more complex and tells me a bit. FWIW.
The comment on mics is interesting because it suggests listener fatigue or some similar thing. I have to believe there are real differences between mics. I only have a Shure dynamic vocal mic, and an import large diaphragm condenser mic, but they seem very different in response. My test is ongoing for just that reason. Maybe I'll hear something I missed if I'm more relaxed. FWIW, some of my favorite test tracks are Joan Baez Diamonds and Rust from the UK import CD, or a transfer of same I made from vinyl. The opening notes have a squeak that should be just right, not to mention her voice, and there are some quiet and low frequency drums I find telling. Also, Pachelbel from an Archive CD (Reinhard Goebel) is more complex and tells me a bit. FWIW.
Ever seen 30 year old silver plated RF connectors? Yecch! OTOH, I've read that gold gives you no real connection improvement unless both parts are gold plated/flashed. No idea if RCA connectors that are externally plated all have gold plated inner contacts, but I wouldn't be surprised if some of them cheap out. Tin plating should be fine for my tin ear 
Oddly enough, silver oxide is a relatively good conductor (the only metal oxide that is) which is why you see it so widely used in microwave connectors and in precision rotary switches amongst others.
Silver has lower resistance per unit area than gold regardless of what it is in contact with.
Silver oxide does look pretty nasty. I have cleaned up surplus connectors and switches by dipping in one of several commercially available silver cleaners like tarnex with surprisingly ok results. (Just make sure to read the label and check that it won't attack or react violently with other materials present in the item to be dipped.)
Silver has lower resistance per unit area than gold regardless of what it is in contact with.
Silver oxide does look pretty nasty. I have cleaned up surplus connectors and switches by dipping in one of several commercially available silver cleaners like tarnex with surprisingly ok results. (Just make sure to read the label and check that it won't attack or react violently with other materials present in the item to be dipped.)
Skin effect causes one thing. It causes the current density to head towards the outer surface. This raises the resistance of the conductor, and it lowers the internal (or self) inductance of the wire.
The internal inductance of a round conductor is 15 nH per foot, this asymptotically reduces to zero at infinite frequency.
Hawksford used the skin depth approximation formula. He applied it outside the accurate realm for that approximation equation.
If you read the article closely, he also substituted steel magnetic wire for copper when he took the scope photo's..(this on page 63, five lines down from the heading "Theory vs Measurement"). He ignored the internal inductance increase caused by the use of a magnetic wire..I was informed that the steel relative permeability was 100, giving 1.5 uH per foot inductance that was unaccounted for in the math..
Hmmmm.
Cheers, John
janneman said:
Yes, when the frequency goes up, the inductance drops. But it can only drop 15 nH per foot..
If you go through the math, you find that a cylinder of conductor which is carrying current, has no internal magnetic field. A coaxial outer conductor really has no internal inductance to speak of. And, as the frequency goes up, eventually all the current will be on the surface (sic) of the wire, with no internal magnetic field, hence no inductance.
By impedance, you mean the resistance of the conductor? That goes up with frequency.
Cheers, John
PS...my avatar is a depiction of the magnetic field intensity of a dual coax cable formed with an inner braid and an outer braid. Two things of interest, first note there is no magnetic field inside the inner braid, nor outside the outer braid, only between.
The outer field is cancelled by virtue of the summation of the external fields of both braids, where they oppose each other and therefore cancel. Between the two, there is the standard 1/r falloff of intensity typical of all round conductors. Between the two, the field is entirely due to the inner conductor's current.
jneutron said:
Yeah, that's what I thought. Impedance goes up with freq because impedance (disregarding R for the moment) is wL. But I thought you said L was going down. I'm not an hf guy and I'm not sure I understand the significance of 'no internal inductance'. Does that make any difference for the inductance we measure on the wire?
Jan Didden
janneman said:
Ah, sorry for the confusion.
First, a definition. Inductance.
Inductance is the relationship between the current within a system and the amount of energy that is stored in the system in the magnetic field.
E = 1/2 L I2
or, L = 2E/I2
For a solid wire....one foot long, it will have an internal inductance of 15 nH at frequencies where skin effect does not have a significant effect. The magnetic field in a solid round conductor is zero at the center, and increases linearly as you go to the surface of the wire..this a consequence of the circular integral around a constant current density...outside the wire, the field will drop as 1/r, this time a consequence of integration about a constant total current but increasingly large area.
janneman said:
Yes. As you increase the test frequency for an inductance measurement, you will see that the inductance reading is dropping. For a zip run as an example, inductance at a Mhz or so will be about 30 nanohenries per foot lower than at 100 hz.
Cheers, John
ps..@sy
was on vaca...had a glass of pino noir...ok, doin good..
Second glass.....ARRRGGHGHGHHGH!!! Yuck...
Bad cork...ewwww, never had that before...
Where wuz ya when I'z needed ya?
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