Superconductors!

Superconductors transition into a state where constant “screening” currents on the surface react such that the conductor effectively repels all external magnetic fields. In terms of field lines they just curve around the conductor, none passing through.

Now… Might this… Possibly… Maybe…?.. Be useful for audio cabling? No inductance.

I repeat: NO INDUCTANCE.

The loss of resistance is a point of course, but I assume it’s not particularly useful in signal audio - only power transmission. And yes, maybe screening too.

I haven’t found any stories of people using superconductors for audio, link me of you know any.

Maybe some aficionado in CERN has secretly used some of their liquid helium for such a project…
Also please do correct me if I haven’t actually understood.

Let’s talk about superconductors.

still holding out for room temperature superconductors, me (just like I’m holding out for cold fusion :wink: )

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Here’s something to chew on…

Graphene is what SR uses in their products…the SR fuses do make quite a difference.

Hope that helps some…

Best wishes

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I wonder if graphene structure’s transition to superconductivity lead to Meissner effect - the mentioned rejection of externally induced magnetic fields. I don’t see why not but then again such high-temperature superconductors might be very different from the usual low-temp Type-I and II.

The definition of superconductivity is when a material reaches its critical temperature and is accompanied by the Meissner effect (Diamagnetism) so it would seem if a material is superconducting it by definition would show the effect. Right now double layer Graphene is superconducting at around 1.7K but there are hopes of Triple Layer which doesn’t have to be twisted to the 1.1deg “magic” angle might give rise to higher temp superconductivity especially when sandwiched between layers of Boron Nitride but we’re a long way off. There may be ways to use what is learned in this approach to understand superconductivity in Copper Oxides and also may lead to higher or dare I say it room temp superconductivity. Dave Goldhaber-Gordon out at Stanford is doing work in this area, you might learn more by checking out his research.

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The question is, would we really achieve zero inductance audio cabling due to Meissner effect, in an achievable way even in experimental conditions.
Capacitance I assume behaves as it always does.

About resistance, there are AC losses in superconductors but I assume this is negligible.
In practice I’m dreaming of a (possible today) cable that’s near resistanceless and without inductance, capacitance handled with geometry, this cable being encased in liquid helium piping and I’d guess it’d be “without” dielectric in this context, save for the liquid helium. Helium is the best dielectric anyway…

It would take whole new load out of tubes to think in
this rarefied atmasphere… :innocent:

I’ll jest wait n’ see what ya’ll come up with!! :grin:

Best wishes guys

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Hmm…
@rower30

Well, about minimizing inductance overall without needing superconductors, would an encasing of (for example) precisely oriented pyrolytic carbon near the conductor surface make it diamagnetic enough that it’d be of benefit?
What about the interaction between the conductor’s own field and diamagnetic encasing? If and only if it’s of no harm with optimized interval distance, we could perhaps have an easier time just having the casing be under Meissner effect and have a normal conductor inside. I don’t know, just speculating.

As I understand it Kinetic inductance is the manifestation of the inertial mass of mobile charge carriers (electrons in this case) in alternating electric fields as an equivalent series inductance. Kinetic inductance is observed in high carrier mobility conductors (e.g. superconductors) and at very high frequencies. Whether the audio band is likely to exhibit this is unknown to me but it implies there would be inductance in a superconducting portion of an audio circuit if this was the case. If not and the frequency approached DC resistance at zero would mean infinite current which would be problematic if the audio band would be for all intents and purposes DC when Ghz and Thz is the realm the above applies to. I have to give this some thought though and play with the math before I would venture a strong opinion. Weak opinion is zero inductance is unlikely in all realms,

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Thanks for the knowledge, nice to have an actually superconductor knowledgeable participant in the discussion, since this is in terms of audio at least, kinda esoteric.

Thanks, I went quickly though the math, really cursory but it looks like the inductance in superconducting wire would be the normal inductance squared! Not the result I expected. Now I am in a rabbit hole, see you in a couple days, maybe I’ll know better or my wife will be mad I haven’t left my office for two days!

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Self-inductance? But due to Meissner effect we could still shield closely spaced conductors from each others’ inductive influence, right?

Don’t see how that would help as the individual conductors will have inductance so even if we could we’re still left with inductance in the circuit. Self inductance just adds a voltage in a wire carrying changing current, I am not sure how this relates to the overall circuit nor how it works in a superconducting wire if different than non-superconducting. I can’t find anything specific to that but I’ll see what I can find out. My area is Math, I’ll have to ask the physics folks if they have any insight. Seems like fun brain exercise though, I hope you can get the answers you’re looking for although actual application may be some time in the future

Well my phono ground cable is picking up so much inductive feedback from surrounding fields that I’d like to have a helium cooled replacement to negate the environment’s effect, no matter the self-inductance.
Okay, okay…

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I am rooting for you my friend, who knows what Galen and his team will work out.

The issue here is you are solving “problems” that aren’t the reason audio cables are non linear. It isn’t R, L and C eliminated one at a time. A proper cable needs EVERY variable adjusted in ratios to one another and tertiary effects (skin effect, hall effect, Rs swept resistance, Vp non linearity to name a few) concurrently.

Inductance can never be zero since equal and opposite fields need to be in the same place at the exact same time…true in theory, false in practice. The meissner effect REQUIRES the transition of a magnetic field. Any field requires ENERGY to exist. Where we get energy from is a distortion to that source. When is the last time a superconductors was “free” of energy input?

This Meissner effect happens when electric current loops spontaneously appear on the surface of a material that becomes superconducting in the presence of a magnetic field. These currents create a magnetic field, similar to that of an electromagnet.

If we remove all resistance, we will also find that limiting Vp differential across frequency become very difficult with moderate capacitance. The denominator of the analog Vp differential equation contains R and C. Remove a passive “R” and we are now required to use just a REACTIVE variable, “C”. Not good.

We need to view analog issues in a total 3D relationships and not assume we can remove one or two variables, and not torpedo critical attributes that are directly related to coherence across the audio band.

I know fancy carbon this or that are all the rage, but for the wrong reasons. Passive “R” can be put to good use improving how our analog cables Vp linearity is improved WITHOUT resorting to too much capacitance. Resistance is NOT a problem.

For fiber optics and even Ethernet, we INCREASE the “opposition” to a signal to IMPROVE the signal integrity. Too low a resistance is BAD, as RL (Return Loss reflections) in either medium can only be electronically canceled to a point. What do we do? Use 26 AWG patch and insert optical attenuators to a system to allow better signal to noise properties. Those changes absorb back reflections that lower the signal over the noise. More “R” used right is better.

If you put a zero resistance wire into analog cable, you will NOT like the true measured results. Not even a little bit. The physics we have from time immortal say we can’t eliminate resistance in analog frequencies without increasing Vp non linearity.

How do we know Vp changes as frequency drops? Here is a chart, Coaxial Cable Characteristic Impedance vs Frequency
I used one that is NOT mine on purpose, the physics don’t do sales and marketing. And, this is not new information but well hidden from analog cable properties.

What do we see in the above chart? We see the IMPEDANCE go UP substantially (upper yellow trace) at lower analog frequencies. At 1KHz the chart shows 250 ohms.This happens because the Vp decreases, and it is in the impedance equation denominator thus as frequency drops, impedance rises. The Vp is defined with R and C of the cable in the low frequency region. We don’t get the nice FLAT 50-ohm curve we see at RF. We never will. Vp goes to ZERO at DC when the signal is there all the time steady state (I don’t count the impulse function when the switch is flicked on) and goes to the RF limiting Vp at RF. We see a transition in the speeds of frequency in the cable as we go from DC to RF. THAT is our big problem in analog cable.

HOW is ANY multi-wire cable (assuming the designer understands what is happening) better? It alters “R” in the Vp differential equation to lower Vp to be more coherent (more the same at all frequencies). If we remove “R”, we are back to square one solving Vp issues with too much reactance. Opps.

Many cable designs increase R (litz wire) and up the capacitance to pretty high levels. Don’t need that as amps get to oscillations with too much capacitive reactance added to the output stage. We have to manage reactance and not just look at resistance by itself.

Each wire, if insulated, is a unique “R” of higher value than one wire of the same aggregate CMA wire area. The total current splits into each wire based on it’s resistance. This is the “R” value in the equation. Capacitance is distributed in parallel so every wire sees the total parallel capacitance. That is the “C” in the equation. Changing C and R alters how a cable measures in the analog time domain.

At RF, we have a different problems. R become a VECTOR (sum of the reactance and resistance). Impedance = SQRT (L/C) at true RF. The wire resistance is the SKIN depth only, not the entire wire cross section. Cable can go into a NIC card and be terminated into the RF “impedance” that is a pure resistor. A good RF cable looks more resistive. The attenuation of RF cables is mainly resistive attenuation and rises with the square root of frequency. If a RF cable deviates from it’s resistive nature, we get increased RL reflections even if the reactive vector is 100-ohms. Part of that is “stored” energy and bounces around. Yep, a perfect 100-ohm cable can have poor RL and an impedance below or above the target impedance can have better RL. Don’t get carried away, to a point this is true.

Vp is flat with frequency at RF. It is the 1/SQRT(e). The dielectric is what defines Vp at RF. Not so in the audio range. We have no group delay problems at RF, well, a tiny bit if the dielectric isn’t RF stable.

Some of these “RF” advantages properties won’t improve analog cable. Nope, they won’t. Can they make analog cable impedance flat with frequency? No. Can they eliminate the group delay (changing Vp) across frequency? No. I don’t see superconductors helping in the audio band.

RF, yes, as attenuation is the square of the frequency. That fact really impacts attenuation. Skin effect at RF says that if we adjust the wire surface area, we reduce attenuation. This is why and RG59 is worse than an RG11 for attenuation. A resistance less surface area will lower attenuation, too. This is why we add SILVER topcoat at RF if we want to tweak attenuation to the absolute best for a given design.

Our ears hear TIME based issues in the analog domain not resistive, which are passive. The better we can get cable non linearity in the time domain, the better the cable at moving data from A to B with low distortion. How good better has to be is always discussed. Analog is a summation of ALL the errors in the system so every option to eliminate the errors is concatenated into the next. Analog error is in total, not a stage.

Making stuff better and better SLOWLY drives the price of that perfection DOWN. No one will reject a better cable (or anything) at the right price. Why would we? Cable can be made better in the analog domain with known engineering, it is just complicated to do it and too low volume to support it. The 80% of the performance at 20% of the price rules. That ratio improves with volume, and understanding.

Best,
Galen

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Well now… Impressive, Galen, yet again. Thank you wholeheartedly for the actually understandable lecture about a subject whose workings are extremely complex. (The deeper we go…)

About resistance, yes as I maintained originally, a passive benefit in analog mostly… Now this actually inspires to learn about the other side of the thread’s coin, low resistance conductors. Carbon (not even supertech nano variety) has had success as conductor in a handful of lesser known designs, gotten praise. (VDH)
I assume I’ll stay on the analog side for what to learn and maybe earn with, so by your lecture I’ll try to forget superconductors in this vicinity of things. Except power transmission, of course.
The Vp concept I somewhat understand, maybe there’s more answers to it in surprisingly low resistance materials, aside geometry.
Diamagnetism, still, interests me as a potential means to improvement. Maybe.
Bismuth?

Gotta admit, I’ll be a novice for quite a while onwards.

What about mains lines and power cords? Are there drawbacks to superconductors here? What about transformers? Classically one’d think they’d be just about “made for it” but… Magnetic issues?
@rower30

Those power systems are 50 or 60 Hz, so we don’t have Vp issues with ONE set frequency…there are no other frequencies to screw up! Superconductors away!

For power cables we want low DCR and low inductance for current demans. We also want the load power factor to be near 1.0 (resistive) for best efficiency. Many systems add reactance to get the power factor near 1.0 to improve electric rates.

Moderate capacitance isn’t a big issue on a power cord as it HOLDS a voltage under current delivery. That we want, to hold the voltage steady as power is applied to a load. Don’t get too crazy with this, the capacitors in the power supply do that job far better than a power cord ever can to hold the voltage steady!

If you look at large amplifier reviews, you will see that the line voltage sags with current draw. A sign of too much for the wall to deliver under the resistance of the leg power is drawn from. E=I*R so as we draw more current, the voltage dropped across the line increases. This makes line voltage go from 120 volts to even a low as 110 volts.

If you use tubes, this is really bad for the BIAS and thus the tubes linearity.

The P20 and like devices add capacitors to “help” smooth this out by using current from the capacitors, and not the wall circuit leg under peak current demands. But…it can only work so long as the caps deplete their charge.

Best,
Galen

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How’s this in the superconductor context? Does near-zero resistance allow for surplus apparent power delivered, depleting the power factor ratio?