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The best dialectric is air ´cos electrons travel not only along cables but also around them.

Discussion in 'd.i.y.' started by Chris, Aug 9, 2019.

  1. Chris

    Chris pfm Member

    Any opinions on this wrt DIY i/connects in oversize tubing ??
     
  2. JensenHealey

    JensenHealey pfm Member

    Electrons most certainly do not travel around the cables. The electric field does.
     
  3. Vinny

    Vinny pfm Member

    Dielectric?

    Electrons drift in a general direction when a voltage is applied but the movement of individual electrons is essentially random.

    Define what is meant by "best", please.
     
  4. Chris

    Chris pfm Member

    I’ll leave the definitions for those that know. I’m just asking if there could be anything in it, with a view to improving my I/cvs by using solid core inside an oversize thin walled FEP tube , in other words surrounded by air. Something to do with Oliver Heaviside, famous for his discoveries as a telegraphy wallah.
     
  5. Vinny

    Vinny pfm Member

    A dielectric is a polarisable insulator.
    Being a good dielectric (easily polarisable) is extremely advantageous for the insulator in a capacitor, however, the question appears to be aimed at cable insulation, and that is where things get complicated. My educated guess would be that insulation is best being a poor dielectric. But I stand to be corrected. Air is commonly used as a dielectric because it is essentially free.

    The dielectric constant for vacuum and pretty much all gases are very similar - around one. By contrast, tantalum pentoxide, the dielectric in electrolytic tantalum capacitors, has a dielectric constant of around 27. Plastics generally have DC's in the region 2-3.
     
  6. John Phillips

    John Phillips pfm Member

    Looking at cable dielectrics from the "best" point of view, there are at least two possible alternatives.

    From one PoV, the "best" dielectric has no audible impact on the signal. In this case the most helpful way to ask the question is to ask whether any particular dielectric (air, PVC, PE, etc.) audibly degrades the signal (and preferably understand how and to what extent).

    If someone is looking for an enhancement to the signal caused by the dielectric then it's a completely different question. And as @Vinny asks above, it become a matter of what the OP defines as an "best" (and I guess if this is the case, how other contributors may define it).

    Coming personally from the first of these points of view I experimented in the early 1980s with making up cables from all sorts of materials and concluded it was only really worth being concerned with good cable construction. YMMV, of course.
     
  7. Vinny

    Vinny pfm Member

    Having compared screened and unscreened interconnects, that must produce, pure guess, one trillion times any effect of changing insulator. Speaker cables...…………..pass.
     
  8. Chris

    Chris pfm Member

    Ok, thanks. My question remains: might it be a good idea to try knocking up some interconnects which consist of solid core OFC copper sheathed loosely by an oversize but flexible thin walled FEP tube ? I can bodge the mechanics but the electronics side of things includes me out or should I stick with my Johnny Audioorigami I/cs - Van Damme, I think.
     
  9. Vinny

    Vinny pfm Member

    I think John answered that one from personal experience.
    Are such things available commercially?
    Why?
     
  10. awkwardbydesign

    awkwardbydesign Officially Awesome

    If you're going to worry about the dielectric, you will need to worry about this too. https://en.wikipedia.org/wiki/Triboelectric_effect
    Have fun. :D
     
  11. juz400

    juz400 pfm Member

    Only ever seen copper tubing used for water cooling PC hardware in the `Domestic DIY` sense, I dont know if someone has ever `hard wired` copper interconnects from one HiFi component to another
    Fascinating video here for inspiration if anyone wants to give it a go :) and theres some serious Valve porn from 19min50sec

     
  12. sq225917

    sq225917 situation engineer

    Mint video.
     
  13. martin clark

    martin clark pinko bodger

    Re: copper pipe - NVA did some silly interconnects based on a small-diameter semi/ hardline copper coax (i.e. copper tube outer, c 3,mm dia)
    I have one in the autopsy box, a din-din affair in which the guts hidden inside a lot of techflex & heatshrink - received for free because, guess what, being a hand-formable but otherwise- totally inflexible thing, it failed somewhere inside - likely at a solder connection inside the plugs.

    And I cannot be a^r$ed to fix it, because it's a daft idea.
     
    JimmyB likes this.
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I once worked on induction furnaces where the conductors were copper pipes with distilled water running through them to keep them cool... 3 phase 11KV!!

    Of course for the ultimate hi fi dielectric simply remove all the air from the listening room, but keep yourself grounded via a tin foil hat.... Special award for the first to try it!
     
    narabdela likes this.
  15. martin clark

    martin clark pinko bodger

    snigger.

    Or simply displace the room's air with sodium hexaflouride for bass to die for ...
     
    Arkless Electronics likes this.
  16. Pete MB&D

    Pete MB&D Pete Maddex, the one and only!

    I used to make up different cables for 62 to PSU using all sorts of cables, separate wires for power and screened signal.
    The best turned out to be cat5 stranded patch cable using one of each pair for signal/power and grounding the rest, it fits nicely into a DIN plug and comes in nice colours.

    Pete
     
  17. davidsrsb

    davidsrsb pfm Member

    You can see an example of TV transmitter air spaced rigid coax at the top of this link. The space is usually pressurized with dry nitrogen rather than air to prevent water getting in or corrosion
    http://necrat.us/biz/wp/?tag=transmitter
     
  18. John Phillips

    John Phillips pfm Member

    At the time I experimented I was working in a 1,200-person research campus and off-cuts/discards of all sorts of cables, materials, etc., from the commonplace to the exotic, were readily available with which to experiment. I am sure FEP tube etc. can be found today but I am not sure about getting small quantities.

    To return to the OP's question, one of the key differences (perhaps the key one) is "dielectric constant" (AKA relative permittivity). Air has a DC of close to 1. Dielectrics suitable for making audio cables have a DC typically between 2 and 4. High DC means high capacitance all else being equal. This usually does not matter unless (i) the cable is connecting a cartridge to a phono preamp; or (ii) the cable is long and the electronics driving it has a high output impedance.

    In case (i) you may need to match the cartridge with an optimum capacitance to get the best out of the cartridge. Low capacitance cable may need to be part of doing that.

    In case (ii) the output impedance of the electronics plus the capacitance of the cable form a low-pass filter. In rather unusual cases this may reduce treble. So air is "best" because it has a lower dielectric constant but in almost all situations other dielectrics are perfectly good enough and there's no audible signal degradation from this effect.

    Dielectrics have other properties and imperfections. I couldn't hear any differences then but I am sure I now have sources and equipment with more resolution, so my conclusion then may validly be questioned. However, I now have rather older ears, and I no longer feel the need to experiment in this way.
     
  19. eddie pugh

    eddie pugh pfm Member

    David srsb

    Is that not commonly referred to as a waveguide or are they square with no internal conductors. I once worked on a site constructing an early 1072 'ish Goonhilly style satellite transmitter / receiver station and the link to the local cilty was by microwave The main connection between the cryogenic amp kit and the microwave transmitter tower was a substantial accuraately cast rectangular box section !! Always amazed me

    eddie
     
  20. Jim Audiomisc

    Jim Audiomisc pfm Member

    Various forms of HF/VHF/UHF/Microwave coax employ internal constructions where the material between the conductors is a foam, or 'spider' or similar to replace as much of the dielectric with 'air' as possible. This reduces capacitance and slightly reduces loss/metre at high frequencies. (i.e well above audible frequencies)

    Similarly 'rigid' and 'semi-rigid' coax is commonly used for 'microwave systems'. I've used them more than once. The main drawback being the rigidity.

    I've also used 'low loss UHF coax' for years as interconnect cable for audio. Simply because it gives a low capacitance per metre and - buying a 100 m drum - a lot cheaper than fancy cables. 8-]

    BTW 'Standard Waveguide' tends to be a 2:1 ratio rectangular metal pipe. However for audio this would have two slight snags.

    1) The dimensions have to be a half x quarter of a wavelength of the lowest frequency you want it to carry. Slightly awkward in a normal living room if you want to get down to 20Hz. 8-]

    2) These guides are dispersive. i.e. the time taken to travel along them varies with frequency.

    They're also multi-mode if you use too high a frequency, and I suspect that'd be a PITA as well for audio.

    So I'd suggest sticking to coax or twin feed.
     

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