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Thread: Do mains cables make a difference??

  1. #261
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    Yes, electrons do oscillate around in a heat dependant random manner which is Brownian motion producing thermal noise, and this manifests as the noise audio wants rid of.

    I wrongly didn't state that the velocity was an average, and refers to electrons being 'driven' by an applied voltage, which results in a velocity of only a few mm/sec.

    Can't remember all of the noise types but shot noise, partition noise, and flicker effect come to mind. (college 45 years ago).

    V (noise) = root (4kBTR) volts, where k = Boltsmans constant, B = bandwidth, T = absolute temperature, and R = resistance.
    Last edited by Pharos; 03-06-2018 at 22:00.

  2. #262
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    Quote Originally Posted by alphaGT View Post
    I have had this discussion with a friend in Italy, who claimed that as alternating current was moving back and forth at 50Hz, (60 here in the States), the electrons were only moving back and forth in the “good”, copper.

    So I did some math, it’s in a notebook around here someplace, if I ever find it I may share it. But basically I found out his theory was rubbish. The electrons were moving far further than two meters or less. Like some portion of a kilometer. So, yea, so much for promising theories.
    The maths are quite straightforward.

    Assume the conductor is copper, which has about 8.5 1028 conduction electrons per m3.
    Each electron carries a charge of 1.6 10-19 Coulombs.

    So in a 1 metre length of wire, 1mm in diameter, there are 6.7 1022 conduction electrons with a total charge of about 104 Coulombs.

    A current of 1A corresponds to a charge flow rate of 1 Coulomb/second, so at that rate it would take 104seconds for the total conduction charge in 1 metre of conductor (with a diameter of 1mm) to flow past a given point. Thus the average drift velocity is 0.1mm/second.

    So for an AC mains current alternating at 50Hz, during the first half cycle of 10ms, the electrons will drift 0.001mm, and in the second half cycle they will drift 0.001mm back again.

    However despite the small drift velocity, the individual electrons are subject to thermal excitations and these give the electrons a much higher Fermi velocity of about 1.6 106m/sec, or about 1010 higher than the drift velocity. Despite the high Fermi velocity electrons do not travel at this rate because they undergo collisions and are constantly being deflected from a straight line path. Owing to thermal excitation of the copper atoms, the conduction electrons are deflected because of this interaction. It is this interaction that results in the positive thermal coeffcient of resistance of metals. As the temperature rises so does the vibration of the atoms and the probability of an electron being deflected increases. The mean free path between collisions falls, so the acceleration by the electric field has less effect before the electron is deflecte in more or less random manner. The current produced by a given field falls and this corresponds to a higher resistance.

    Electron scattering will also occur due to defects such as impurities and crystal dislocations (grain boundaries). The effect of these can be estimated because they have a far lower temperature dependance than the thermal scattering effect. If the conductor is cooled towards absolute zero, the resistance doesn't fall to zero, but flattens out to a residual value determined by scattering from dislocations and impurities. For oxygen free copper, this residual resistance is about 1/70 (1.4%) of the resistivity at 20deg C; so the impurities make a contribution to the electron scattering of only 1.4%. And even the thermal scattering is low: the mean free path in copper at 20deg C is about 5 10-8m, so on average an electron passes 200 atoms without interaction before being deflected from a straight line path.

    To put the impurity scattering effect into perspective, this contributes ~ 1.4% to the overall scattering. So eliminating all impurities and dislocations would only reduce the resistance by 1.4%. A temperature rise of 2 - 3deg C would add more resistance than the elimination of all impurities would remove.

    Reducing crystal boundary dislocations (often called grain boundaries) and othe dislocations beyond a certain level is pointless because even if a perfect single crystal is produced, the effect of just bending the wire beyond its elestic limit (where it will spring back to its original shape) will be to create massive dislocations of the crystal structure, so such a perfect structure would be near imposible to maintain in practice.
    Have you listened to this month's choice in the Album Club?

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  3. #263
    Join Date: Apr 2018

    Location: Cornwall

    Posts: 78
    I'm Dominic.

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    Quote Originally Posted by Edwardlon View Post
    It seems to me that the 'best' mains cable to use is 2.5 mm ring main cable given that it feeds the sockets anyway. A bit stiff but doable. One could always put some nice braid around it to make it look less 'industrial'.

    My understanding is that for installations that may be subject any kind of movement, then a flex construction cable must be used and using any solid core cable is prohibited.
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  4. #264
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 642
    I'm Dennis.

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    Barry, I think a few steps have been left out in the following, although I may be wrong, could you please fill them?

    "Assume the conductor is copper, which has about 8.5 1028 conduction electrons per m3.
    Each electron carries a charge of 1.6 10-19 Coulombs.

    So in a 1 metre length of wire, 1mm in diameter, there are 6.7 1022 conduction electrons with a total charge of about 104 Coulombs.

    A current of 1A corresponds to a charge flow rate of 1 Coulomb/second, so at that rate it would take 104seconds for the total conduction charge in 1 metre of conductor (with a diameter of 1mm) to flow past a given point. Thus the average drift velocity is 0.1mm/second."

  5. #265
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,468
    I'm Ken.

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    Quote Originally Posted by Edwardlon View Post
    It seems to me that the 'best' mains cable to use is 2.5 mm ring main cable given that it feeds the sockets anyway. A bit stiff but doable. One could always put some nice braid around it to make it look less 'industrial'.

    I've seen this written in several threads around the web, some by EE's. Some say double up the copper thickness on your connecting cable, which acts as a spur, as the in wall cable is usually a ring circuit, so make the spur thicker to compensate. Strip the twin and earth conductors out of the sheath and make a twisted pair out of the L and N and run an insulated earth along side the pair. Cover in an expanded woven jacket and you have a great lead.
    I wouldn't worry too much about what manufacturers say, their recommendations are more about not getting sued if things go wrong, so "change nothing" is the order of the day. Flexible leads are meant for a lot of use/abuse/coiling/uncoiling etc like hair driers/power tools etc. Your audio gear is more of a fixed installation, I only move mine a few times a year and the mains cables tend to stay put, its the gear I move, so not a lot of flexing involved. You can stick your tongue in a live socket if you want, it's not illegal, just not advised.

    I will get round to making a lead like this one day, using a straight exit industrial three pin plug one end and a locking IEC kettle type connector on the other. The Hifi plugs offer nothing other than the ability to accept thicker cable jackets and are a rip off. Industrial plugs offer the same, can be found with Silver plated pins if you want to go that route, and are made from the same materials, so you are paying for the myth that the "hifi" versions are special. I personally only use a three pin British safety plug in one place in my system, and that's where the single mains lead connects between a wall socket and my mains distribution unit. this is the only fused plug in the chain and its there to protect the lead from catching fire and also the ring main, in the unlikely event any of my leads get tapped in a door etc and give a direct short. All the leads from the distribution unit to my gear have IEC kettle type connectors each end, so avoiding unnecessary multiple fuses/connections. I make the IEC leads up myself from decent thickness copper and have no issues with what I hear. The only negative thing I experienced was when I had a filter in my distribution unit, it sapped the life out of my amps, when I removed the cheap and nasty filter and made all the connections straight through, point to point, the problem went away.

    It's a simple approach but works for me, that is the important thing, if you are not experiencing any mains issues, don't go chasing rainbows and stick with what you are doing.
    Last edited by Qwin; 04-06-2018 at 09:15.
    Ken

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  6. #266
    Join Date: May 2009

    Location: Bristol

    Posts: 3,900

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    I have removed all mains cables from my system. The noise floor has dropped considerably; the blackness is inkier than ever, and, if I close my eyes, the speakers disappear.

  7. #267
    Join Date: May 2016

    Location: Gloucestershire

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    I'm Ian.

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  8. #268
    Join Date: Mar 2017

    Location: London N2

    Posts: 742
    I'm Edward.

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    Quote Originally Posted by nonuffin View Post
    My understanding is that for installations that may be subject any kind of movement, then a flex construction cable must be used and using any solid core cable is prohibited.
    Ah I did not know that. Makes sense.

    Quote Originally Posted by Qwin View Post
    I've seen this written in several threads around the web, some by EE's. Some say double up the copper thickness on your connecting cable, which acts as a spur, as the in wall cable is usually a ring circuit, so make the spur thicker to compensate. Strip the twin and earth conductors out of the sheath and make a twisted pair out of the L and N and run an insulated earth along side the pair. Cover in an expanded woven jacket and you have a great lead.
    I wouldn't worry too much about what manufacturers say, their recommendations are more about not getting sued if things go wrong, so "change nothing" is the order of the day. Flexible leads are meant for a lot of use/abuse/coiling/uncoiling etc like hair driers/power tools etc. Your audio gear is more of a fixed installation, I only move mine a few times a year and the mains cables tend to stay put, its the gear I move, so not a lot of flexing involved. You can stick your tongue in a live socket if you want, it's not illegal, just not advised.

    I will get round to making a lead like this one day, using a straight exit industrial three pin plug one end and a locking IEC kettle type connector on the other. The Hifi plugs offer nothing other than the ability to accept thicker cable jackets and are a rip off. Industrial plugs offer the same, can be found with Silver plated pins if you want to go that route, and are made from the same materials, so you are paying for the myth that the "hifi" versions are special. I personally only use a three pin British safety plug in one place in my system, and that's where the single mains lead connects between a wall socket and my mains distribution unit. this is the only fused plug in the chain and its there to protect the lead from catching fire and also the ring main, in the unlikely event any of my leads get tapped in a door etc and give a direct short. All the leads from the distribution unit to my gear have IEC kettle type connectors each end, so avoiding unnecessary multiple fuses/connections. I make the IEC leads up myself from decent thickness copper and have no issues with what I hear. The only negative thing I experienced was when I had a filter in my distribution unit, it sapped the life out of my amps, when I removed the cheap and nasty filter and made all the connections straight through, point to point, the problem went away.

    It's a simple approach but works for me, that is the important thing, if you are not experiencing any mains issues, don't go chasing rainbows and stick with what you are doing.
    Thanks for that most informative response. I've not done this but may just as an experiment. But I tend to move things around so may not be so useful and as Dominic mentioned probably is not allowed.
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
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  9. #269
    Join Date: Mar 2017

    Location: London N2

    Posts: 742
    I'm Edward.

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    Quote Originally Posted by Joe View Post
    I have removed all mains cables from my system. The noise floor has dropped considerably; the blackness is inkier than ever, and, if I close my eyes, the speakers disappear.

    Lol

    Does remind me of the 2 or 3 times when the mains distribution for the neighborhood blew how quite things were without all the electrical hum. And the real inky blackness.
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  10. #270
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,468
    I'm Ken.

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    Quote Originally Posted by Edwardlon View Post
    Ah I did not know that. Makes sense.



    Thanks for that most informative response. I've not done this but may just as an experiment. But I tend to move things around so may not be so useful and as Dominic mentioned probably is not allowed.
    Not a question of being allowed, like I said, your allowed to stick your tong in a socket if your daft enough, but its not recommended. That is all the specs are, recommendations. Different countries have different ideas about what those might be. It's a different matter, if your a manufacturer and are selling to the public, you have to follow the guide lines to get certification and could be prosecuted if producing something which was inherently dangerous and caused loss or injury. I quite often run my Amp with the lid off, when I'm testing things, you would never see a new one for sale like that. Do what you are comfortable with, within the realms of your knowledge/experience, that's all I'm saying.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + AT 33PTG II / AQVOX Phono 2 CI / Pro-Ject Pre Box RS / ESP Active X-Over / Nakamichi AVP1 Power / Modified semi-active Yamaha NS1000M Speakers / Stello CDT100 Transport / NAD M51 DAC.

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