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RFI : how does it affect mains circuitry of hifi equipment?

Discussion in 'audio' started by Ragaman, Feb 20, 2015.

  1. Ragaman

    Ragaman Mentalist

    This, in my opinion is the only question that needs answering when it comes to the subject of mains cables.

    Russ Andrews company have already had 2 of their cables fully scientifically tested by an independent lab who confirmed from scientific testing that the cables removed RFI from the mains, namely a russ Andrews classic powercord & one higher up in the range, both were confirmed to do so, this part of the mains equation is unquestionable so we need to move on to the next step

    The question is, what affect does RFI have on the mains circuitry of hifi equipment, is it detrimental to sound quality, if so, why? & how?
     
  2. Purité Audio

    Purité Audio Trade: Purite Audio

    Simple internal shielding of sensitive components is completely standard on any competent
    design , should be a non issue.
    Keith.
     
  3. benfield

    benfield Active Member

    Interference is interference. If the signal fed to an amplifier changes, the output changes. A similar result is obtained if the 'rail voltage' of the power supply changes whilst the signal remains the same.
     
  4. abbydog

    abbydog pfm Member

    Oh yeah - and sugar is a health food, says raw cane supplier.
     
  5. Ragaman

    Ragaman Mentalist

    It has been scientifically proven, exactly what people ask for when it comes to any kind of claim, it is unquestionable , sorry.

    The independent lab results show this to be true.

    The next part is what needs to be answered, if it can, then maybe the mains cable debate can move on from the usual anecdotal arguments.
     
  6. YNWOAN

    YNWOAN 100% Analogue

    As I recall the RA sponsored research showed a small level of rejection at very high frequencies (well above the audio band) so it's a bit of a leap of faith to say the case is proven. It can probably be shown that insects striking the windscreen infinitesimally slows the car but that doesn't mean that such a problem is of relevance.
     
  7. Julf

    Julf Evil brother of Mark V Shaney

    Only if it interferes. Most power supplies provide pretty good isolation between the mains side and the output.
     
  8. JohnW

    JohnW Trade: Lakewest

    Ragaman,

    RF is an issue, when I'm performing Dynamic range measurements on almost any item of audio equipment I need to unplug my Ethernet over Mains adaptor to prevent mains Bourne RF effecting the results - I clearly see the noise on my FFT plots.

    Any Silicon junction device (Transistor, Jfet, Mosfet) will demodulate RF (Think of an old Crystal radio set) - its the effect of these demodulated products that could "foldback" into the audio bandwidth that's the concern.

    I doubt that some of those expensive mains leads that claim to suppress RF interference are the most cost effective way to reduce RF energy into a unit.

    We have all heard the TDMA noise (Burst of blips / tones) our phones induce into audio devices when placed too close.... its an extreme case of RF interference, but it happens all the time at much lower levels.... it adds "hardness" to the SQ.
     
  9. Ragaman

    Ragaman Mentalist

    Please show your findings, this is incorrect, if it was correct the company could not have carried on advertising their cable.
    I'm sure if you contact russ Andrews they can supply you with the results of the tests.
     
  10. Julf

    Julf Evil brother of Mark V Shaney

    It is always the pronouns that are the problem.
     
  11. Ragaman

    Ragaman Mentalist

    What is "pretty good" isolation & do different amplifiers have different levels of isolation, would a high end product with more expensive mains transformer have better isolation than a cheaper budget component?
     
  12. Ragaman

    Ragaman Mentalist

    Have a go at the person when you can't have a go at the evidence.

    Not university educated but far from the point of the thread.
     
  13. Julf

    Julf Evil brother of Mark V Shaney

    I am sure you are familiar with the term "weasel words".

    From the ASA ruling:

     
  14. Julf

    Julf Evil brother of Mark V Shaney

    It had nothing to do with you or any education (or lack of such). My remark was purely about the fact that unless we define what we mean with "it" and "this" refer to, we really have nothing to go by.
     
  15. JohnW

    JohnW Trade: Lakewest

    Julf,

    This is simply not true - most PSU have practically ZERO isolation at higher frequency where even a few pF of capacitive coupling is all you need to act a signal path between domains.

    At best PSU will have decent attenuation within their regulator loop Bandwidth (think say 1KHz BW) + any LC filtering, but even this LC filtering beyond say 10MHz is starting become ineffective (normally much lower) .

    Typical Bulk electrolytic's are useless much beyond say 50KHz...

    A typical PSU is not a defence against any level of RF, this is left to localised RF decoupling - which is typically not considered in most audio designs.
     
  16. Ragaman

    Ragaman Mentalist

    petty
     
  17. JohnW

    JohnW Trade: Lakewest

    I'm not supporting expensive "RF Suppression mains leads" as I don't believe they offer good value for money / performance, only that RF can and does effect audio quality.

    Paul Miller used to run injected RF / Audio sweeps that clearly showed the effects of external RF on measured audio performance.
     
  18. YNWOAN

    YNWOAN 100% Analogue

    Ragaman, I don't really care that much one way or the other. You say my recollection is incorrect well let's see your evidence to support that claim. The company carried on advertising their cable because they modified the way they promoted their claims. I'm sorry but I have no interest in contacting RA on this matter - so far your claim is an unsupported by evidence as mine is but the difference is I'm not claiming case proven.
     
  19. Ragaman

    Ragaman Mentalist

    Every time I read a cable thread, the same old questions arise, please can someone show, scientifically, under lab conditions (not in the home) that a mains cable can indeed remove RFI, I believe you are constantly requesting results that show such things to be true, the cables were tested as requested by many & the results were shown to prove that RFI was removed from the mains

    This thread is not regarding if than can be achieved as this has already been done but rather, how does it affect sound quality once it enters the component,

    johnW has shown some interesting results but still the question is , does it lower sound quality & if removed improve upon it.
     
  20. YNWOAN

    YNWOAN 100% Analogue

    In the greater context - I don't think there is much disagreement on that; but is RF an issue for mains leads and, if it is, does that impact on the equipment attached to it?
     

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