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

Lee T

pfm Member
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?
 
Simple internal shielding of sensitive components is completely standard on any competent
design , should be a non issue.
Keith.
 
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.
 
Oh yeah - and sugar is a health food, says raw cane supplier.
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.
 
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?

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.
 
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.
 
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.
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.
 
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.

It is always the pronouns that are the problem.
 
Only if it interferes. Most power supplies provide pretty good isolation between the mains side and the output.
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?
 
Please show your findings, this is incorrect, if it was correct the company could not have carried on advertising their cable.

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

From the ASA ruling:

We noted the evidence supplied by Russ Andrews Accessories represented the results of tests carried out under lab conditions to industry standards and considered that the results appeared to show a reduction in decibels compared to a normal mains cable (which was used as a control). However, we understood from Russ Andrews Accessories that these test results were not necessarily indicative of perceptible noise reduction in consumer relevant conditions and noted the results did not indicate a difference in perceptible RF (radio frequency) interference (in Common or Differential Mode) when using the standard leads against which the Superkord and Powerkord products were being compared.

We noted the ad included the text "What don't the plots show us. The plots show how the cables perform under test in laboratory conditions. Whilst we could infer that the same level of rejection occurs in a domestic environment (i.e. when the cables are plugged into a Hi-Fi or Home Cinema System) we are not claiming that they do. Similarly, the graphs do not prove that the rejection measured in the lab has a perceptible (i.e. audible) effect when the cables are used in a Hi-Fi or Home Cinema System". Although the rest of the ad provided information (including graphs) about how the product worked to reduce RF noise and that such results were evidenced from independent lab testing, we considered that consumers would understand from the qualifying statement that the reference to the lab results did not necessarily mean that the same results would be achieved by consumers in the home. We considered that the evidence supplied was therefore sufficient to support the claims in the ad about the extent to which RF interference was achieved when tested under lab conditions. We concluded that the ad was not misleading.
 
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.

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

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.
 
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.
petty
 
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.
 
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.

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

From the ASA ruling:
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.
 
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.

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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