1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

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. davidsrsb

    davidsrsb pfm Member

    No, waveguide is empty. Transmitter feed use these air space rigid coax pipes with a rigid centre conductor held in place by spacers.
    It's a nightmare getting the sections to site on a mountain on the back of a lorry up a windy road.
    When you are transmitting at 100s of KW in the UHF, cable loss gets very expensive in electricity bills.
    This is not important at audio frequencies
  2. Dan K

    Dan K pfm Member

    Is the real question not simply that the OP wants to build the best DIY cable that he can? That one's been answered plenty of times.
  3. suzywong

    suzywong Shifting 0s & 1s since 1968

    I have a couple of semi-rigid interconnects with RCA plugs on each end. They came with a Meridian DAC that I bought off eBay.
  4. Jim Audiomisc

    Jim Audiomisc pfm Member

    The following points tend to summarise my approach to 'best' interconnect for home audio.

    1) I happly used a standard low-loss UHF TV coax for decades.

    2) I then used some 'Shark' brand co-axo with very generous copper conductors as the inner and outer.

    3) As used here in my audio systems they both still work fine and I use whichever is convenient wrt length, etc.

    4) Since I got (2) from CPC the 'Shark' cables seem to have gone up in price by an order of magnitude or two. So either they were making a big loss on sales in the past or they're living in luxury now. So far as I can tell, its the same cable.
  5. Hempknight

    Hempknight pfm Member

    I've got some 'air insulated' solid core, it has an over sized clear PE tube, and some PE 'wire' twisted around the conductor to keep in centered within the tube, I brought it because I liked the look of it, would be a nice aesthetic for speaker cables, in a dry climate atleast.
  6. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    For those who believe in unicorns etc a cheap way of trying something on these lines is readily available 75 Ohm semi air spaced coax for TV aerials. It usually has a reasonably thick solid core centre conductor but multi stranded may be available. The outer screen can be a bit "stingy" and sparse in really cheap stuff but even the best available will be a fraction of the price of foo cable.
  7. martin clark

    martin clark pinko bodger

    For everyone else interested in coax not designed for audioband use, just try RG-6, a good one like Belden.

    It's also cheap and widely available and contains lots of copper (nb also prob offers significantly fewer unicorns/Km as a result... but if you need a pointless, beefy 7mm dia interconnect, it's fine)
    Arkless Electronics likes this.
  8. JimmyB

    JimmyB pfm Member

    Thought RG6 could also have a non copper core (inc CCS) and a non cu screen (Al).
    I've used Webro WF100 because it's specced as Cu/Cu/Cu but that was an aerial install, never tried it for an interconnect.
  9. Pete MB&D

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

    Thin eithernet cable is good.

    I have a reel in my loft.

  10. Paul R

    Paul R pfm Member

    Original Ethernet cable would be perfect for fooconnects. Everybody would know you meant business.
  11. Pete MB&D

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

    The fat yellow hosepipe?

    With vampire taps and minimum bend radii?

  12. martin clark

    martin clark pinko bodger

    I've the remains of a reel of Belden RG6, acquired likewise, and it is 18ga /0.7mm solid copper central conductor/ Cu screen/ tinned-Cu braid.

    ETA - and as I've said before here - I'd be v happy to post a metre or two or three gratis to anyone who wants a play with some, for the postage cost as a donation to pfm.
  13. davidsrsb

    davidsrsb pfm Member

    There are different types of RG-6 and the cheap CCS core grade is very inferior in RF performance. I would avoid steel core in audio as it is too likely to pick up induced hum
  14. John Phillips

    John Phillips pfm Member

    Also, ferromagnetic materials like steel have hysteresis and can produce intermodulation distortion.

    Given the low level signals involved in audio (and RF receivers) it's not likely to be a problem. However in tests of RF transmitter cables for mobile communication systems some work colleagues measured the IMD of cables. To meet the IMD specification they had to specify connectors without nickel plating. But that was for -137 dB IMD (-120 dBm) referred to a 50 W carrier.

    BTW, no special grader of copper was involved. Where were those pesky micro-diodes at copper grain boundaries?
    Last edited: Aug 13, 2019
  15. G T Audio

    G T Audio Trade: Distributor and Manufacturer

    Thanks for sharing. Reminds me of my days in the Transmission/Repeater rooms at BT but those used waveguides for the transmission... Happy days!
  16. ff1d1l

    ff1d1l pfm Member

    After several decades of cable scepticism, I very recently swapped out a knocked up - non-matching plugs, microphone cable - interconnect between Traffo pre and power amp.
    I swapped it out for another home brew of 0.4mm silver plated copper with no shield in a masking tape sandwich and Maplin plugs. Easily audible difference - and substantial improvement - to the extent Son walks through and says, unprompted, wow, stereo's sounding good today.
    So have some decent plugs, and cotton sleeving on order.

    A little background here, the power amp at the moment is an IMG Stageline STA160 PA amp, £20 from the car boot. It's acquitting itself rather better than you may imagine. I'm using it because all my Luxkit amps are at the menders. I was using two Luxkit Z501s passively bi-amped. Which was a very clean and wide window.
    Nevertheless, a week's listening later, even with the IMG, change is easily audible - improvements in imaging and dynamics and clearer bass.

    Speaks are souped up JBL 4430 (15" bass-mid and pressure unit buttcheek horn) Studio Monitor clones (showed at Kegworth last year), and well able to show up any changes upstream.

    The big Luxkit I have - z504 - is mended and back soon, so I'm very much looking forward to swapping it in.

    So the differences between the cables was the new ones have no screen, are un twisted - parallel in fact, and have thinner conductors. And the dialectric is paper.

    Just going to knock up another to use from Dac to pre.

    If I perceive any difference I'll comment.
  17. sq225917

    sq225917 situation engineer

    Now try plugging the old cables back in, you'll be amazed how much better they sound too now you've cleaned the sockets.
    booja30 and Arkless Electronics like this.
  18. awkwardbydesign

    awkwardbydesign Officially Awesome

    Yes please, I need 3 metres for my loft system. (2 x 1.5m)
  19. ff1d1l

    ff1d1l pfm Member

    Arf arf... sockets were clean. Amp had only been in for a few weeks. Leads swapped around then.

    And, smaller but worthwhile improvement installing some from Dac to pre. Been listening the last few hours.
    And before you say, that lead had been replaced with the former pre power lead when I knocked up the new pre/power lead. So all sockets had plugs plugged and unplugged very recently. Actually, I've never found that to make that big a difference. Deoxiting plugs and sockets a different matter.

    Anyway, I've put methodology and findings before all - no wish to endlessly debate on about this. So, believe it or not, as you please.
  20. sp25

    sp25 pfm Member

    Did you mean sulphur hexafluoride (SF6)?

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice