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Math + Logic + Science = something completely mad...

So, I've done a metric fuckton of research, notwithstanding the clear bias the man who designed and built my Belles has against esoteric cabling.  And here's the conclusion to which I arrived. 

My monoblocks are sitting on top of the speakers.  The distance from the amp to the speaker is barely a foot, which is exactly how long a run of wire I intend to use.  Goal is to minimize the effect the wire has on the sound.  

According to the calculations I've seen and done, the skin effect depth on copper wire at 20Khz is 461 micrometers.  Meaning a 19-gauge copper wire (911 mics diameter) would reduce skin effect to zero.  As in no impact whatsoever on the signal. 
 
Of course, it's actually very difficult to find 19-gauge wire.  18-gauge (1024 mics) is much easier, and the skin effect is near zero, but not quite zero.  Seems to be an acceptable compromise. Could go down to 20-gauge and eliminate skin effect entirely.  If I could find insulated aluminum wire, 18-gauge would eliminate skin effect entirely, because skin effect depth on aluminum at 20khz is 580 mics.  

12 inches of 18-gauge wire produces 0.006 ohms of additional resistance.  20-gauge = 0.01 ohms.  

Frankly, I don't see the value in spending big bucks on esoteric, heavy-gauge wire for this application.  I'd rather make the bigger investment in the 2m runs from the preamp to the blocks, because that's where the wire's going to have a hell of a lot more of an effect on the sound.  

Stepping back to allow you all the opportunity to punch holes in my thought process here. 
jerkface
dletch2
455 posts
 
Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers.


Your short 18 awg cables will work perfectly of course. The resistance is but a minuscule fraction of the speaker impedance. Following that short 18awg is a ton of wire in the cross-over, followed by a lot more small gauge wire in the voice coil. The variation in the resistance in the voice coil due to thermal effects is far more than the total resistance of that 18awg.


Virtually every negative reply you will get will be hand-waving with no quantification as you have done. Keep in mind the wire is 2 lengths, resistance will be closer to 0.016 ohm. That will be consistent with virtually no thermal modulation. It is likely a very small fraction of the output impedance of your amplifier too. At 20KHz, the impedance will be up to 0.022. You did miss one critical element though, inductance. That will be the dominating factor. That will increase the impedance to 0.08 - 0.1 ohm by 20KHz. You won’t hear it, but it will be there. Skin effect is rarely an issue. Inductance can be.

jerkface OP
73 posts
 
Skin effect is rarely an issue. Inductance can be.

Only reason I bothered with the math on skin effect is because so many of these esoteric high-end cables do random weird stuff like adding dielectrics to "phase-correct" the signal.  

Of course, over 1-2 feet of wire, I doubt seriously that the signal could possibly get "out of phase" enough to be audible anyway.  

Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers.

So you're saying that the speaker vibrating the amp will cause microphonics in the tubes?  Or is there a concern about proximity to the magnets?  Certainly I could build shelves, that's an easy thing.  I'm just trying to make sure I understand the problem I'm trying to solve here in order to solve it correctly.  If you don't mind, I'd love for you to go over the science with me here. 
dletch2
455 posts
 
So you're saying that the speaker vibrating the amp will cause microphonics in the tubes?

Yes


Only reason I bothered with the math on skin effect is because so many of these esoteric high-end cables do random weird stuff like adding dielectrics to "phase-correct" the signal.
 

They say a lot of things that are not true. That is why they never provide any useful information. If they provided useful information, no one would buy them.

jerkface OP
73 posts
 
Yes

Even when the amp has isolation feet on it and the speakers are sitting on a concrete floor, which is the ultimate vibration sink?  Asking in earnest, not to be argumentative.  


erik_squires
16,037 posts
 
While I believe that cables matter, skin effect is the biggest piece of hogwash ever.

A more likely explanation for cables sounding different, based on what I've heard, is that the amp and speakers are more sensitive to the miniscule LC and R values than the math would have us believe. Perhaps feedback also plays some role here, but 100% of every cable effect I've ever heard can be explained purely in the frequency domain. Oversensitivity to basic cable measurements could explain it.

Also, most cables are way pricier than the apparent changes they produce.
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