advertisement


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

JohnW said:
That's the root of the misconception, nowadays there is a significant amount of RF energy on the mains supply - SMPS, LED lighting and Network over the mains supply are the worst offenders - the “Network over the Mains” is partially troublesome in my lab – it seeps into the PSU’s on my lab equipment (which are better filtered then consumer devices) – for any performance measurements I need to pull the local network adaptor.

I also had a brand of GU10 LED lamps whose internal SMPS was poorly filtered, again lights off for certain measurements – its really not easy, as there would be times I forget and would have to repeat time consuming tests… after all this time I should know better.

It will be interesting to see what effect isolated spurs in my new lab will have – but they are all returned to the same external Meter box / master Fuse / switch etc.
Click to expand...

Arkless Repairs said:
+1 I have to switch off CFL bulbs on my test bench when doing sensitive noise and distortion measurements.
Click to expand...
Very interesting - thanks.

Julf said:
86ece4b015f601329a5d005056a9545d
Click to expand...
Excellent.
 
darrenyeats said:
Very interesting - thanks.


Excellent.
Click to expand...

I wouldn't read too much into this for the typical user of hi-fi equipment.... I'm talking of effects noticed when trying to measure 0.001% distortion or the noise from a MC phono stage and with the bulb within 1 metre of the equipment under test. The inverse square law applies here so distance from bulb makes a huge difference! Similar effects but often much worse can be a problem with SMPSU's.
Worst case I've had was the power supply of one item of test equipment interfering with a measurement being carried out with another piece of equipment! Much head scratching went on for some time before sussing out that one!
 
Jez, yes I wasn't fixating on the bulbs. If anything SMPSs are my hobby horse, and I'm glad there is some real effect behind it (but that doesn't mean I'm not imagining things, I do realise that!)
 
SMPSU's can be be designed and built to have pretty low emissions etc but as usual it's all down to cost!

As Chief Engineer with Alchemist Products many years ago I remember many arguments where I was trying to get maybe an extra £5 spent on the parts for an amp, which would have made a real improvement to performance, and being knocked back 'cos apparently it would have added £25 to the retail price and caused them to have to put the product above the "critical" (in managements opinion) £499.99 point where several competing products sat! Suggesting we save the money on the aesthetics by not using gold plated brass control knobs resulted in looks I would have expected if I had suggested they let me have a good time with their wives! :eek:

It was the same at Musical Fidelity... Anyone remember the Odysseus integrated valve amp? It was a great sounding but short lived product... the latter because they were so unreliable that AFAIK everyone made failed within a few months! I analysed the problems and sent Antony Michaelson a memo explaining what all the problems were and how to fix them... including a BOM for the changes required.... it was ignored! An extra £10 on the parts bill could not be tolerated so they were sent out knowing fine well that they would soon be back....
 
About valve amps - are they "more" susceptible to the effects of RFI? Or perhaps more immune to this outside interference?

And do valve amps themselves emit a considerable amount of RFI via the valves or large transformers?

Sounds like I should be unplugging my Ether-plugs which conveniently extend my network to the Den where the boy plays his Xbox.
 
beammeup said:
About valve amps - are they "more" susceptible to the effects of RFI? Or perhaps more immune to this outside interference?

And do valve amps themselves emit a considerable amount of RFI via the valves or large transformers?

Sounds like I should be unplugging my Ether-plugs which conveniently extend my network to the Den where the boy plays his Xbox.
Click to expand...

They are much more immune to RFI and usually generate less EMI than SS amps. Not that anything should be read into this....
 
beammeup said:
About valve amps - are they "more" susceptible to the effects of RFI? Or perhaps more immune to this outside interference?
Click to expand...

One of the points during the Cold War was that the older tube technology the soviets used in their equipment was much more likely to survive even the EMF from a nuclear blast compared to the NATO semiconductor/digital stuff.
 
Julf said:
86ece4b015f601329a5d005056a9545d
Click to expand...

Indeed excellent. It proves Russ Andrew Lab work does reduce RFI in that lab environment. All we need now is to measure the RFI in peoples homes maybe take homes to the lab.

My name is Miss Understanding for the purposes of this thread.

Interesting that the RA lab work only measured CONDUCTED RFI can I infer from that there is little RADIATED RFI? I have a mobile phone mast less than 100m away but it does not affect my HiFi in the slightest. It sounds like it is pointless putting several mobile phones next to my kettle leads to test if their RFI is radiated into those cables (and hence my HiFi)

I wish I knew what I was talking about.
 
Julf said:
One of the points during the Cold War was that the older tube technology the soviets used in their equipment was much more likely to survive even the EMF from a nuclear blast compared to the NATO semiconductor/digital stuff.
Click to expand...

EMP surely?
 
I have gained as audible improvement from upgrading my mains leads but there is a very clear explanation for this, they significantly reduced EMF that was being picked up by my interconnects.

At the time I purchased the cables I'd got a problem by where I could hear mains hum along with a hiss through the speakers from my listening position, particularly on vinyl.

My mains cables had to run quite close the interconnect cables, which ran from source/s to pre then to active crossovers and finally to the power amps. I Could only do so much with cable dressing, I invested in good quality shielded mains cables and they eradicated the problem completely, you have to press your ears against the speakers now to detect anything. The system seemed to improve all round.

Beyond proper sheilding and good quality conductors/terminations, I see little that can be done with a mains cable to produce a notable improvement in sound quality.
 
whatsnext said:
http://www.russandrews.com/downloads/SKtest.pdf

This is the document Ragaman holds as his reason to believe in RFI

let those who have the technical knowledge perhaps advise us as to how relevant the test parameters are to domestica

I shall read it later when I have unwound from work in case my limited physics allows a view.
Click to expand...

First observation our Russ states the mobile phone frequency is 700 mHz - he may be misleading with that statement. Mobile phones apparently use quite a range of frequencies not just 700 mHz. My starting point for this was http://en.wikipedia.org/wiki/Cellular_network#Cellular_frequency_choice_in_mobile_phone_networks I am sure he isn't trying to blind us with science, he said he wasn't

I fully accept I may have mis understood what I read and welcome more informed opinions.

Edit: The powercord range that shows the dip Russ is enthusing about starts at £700+. The cheaper range does not achieve this.
 
sbgk said:
Don't manufacturers just include kettle leads because they expect the customer to change them for something better. Wonder if Arkless could provide some examples of manufacturers saving money on their products.
Click to expand...

No, I wouldn't say so and I've not heard that view expressed by any of the manufacturers I have had dealings with.
 
YNWOAN said:
No, I wouldn't say so and I've not heard that view expressed by any of the manufacturers I have had dealings with.
Click to expand...

Indeed not regarding mains cables.
sbgk is of course on my ignore list as a troll... things like asking for examples of manufacturers saving costs a few posts after I just did exactly that!
 
Back when I was in charge of such things I would have fired an engineer who designed anything which was susceptible to mains borne RFI.
Any kit needing a special cable to make it work properly from an RFI interference POV has been poorly designed and is unfit for purpose.
IMHO.
 
JohnW - thank you for providing some sanity.

& "Hardness" is exactly the effect it has.


JohnW said:
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.
Click to expand...
 
whatsnext said:
I repeat the ASA decision their ruling was entirely based upon if RA was misleading
and found he was not because his wording was he believed it would be effective in the domestic environment, he did not say it would.

<snip>

Why was Russ so unwilling to say they do remove RFI instead of it is his belief? He knows his cables will not remove RFI.

If anyone wants to follow the teachings and beliefs of Russ A that is their right.
Click to expand...
This seems eminently sensible. No surprise it has gone essentially unnoticed.
 
I am happy to also be called Miss Guided or Miss Leading as long as you don't call me Miss Taken.

From the big stick Russ Andrews document who said

"Whilst we could infer that the same level of rejection occurs in a domestic environment (ie. 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 (ie audible) effect when the cables are used in a Hi-Fi or Home Cinema System."​

Now that seems pretty clear to me. Why do others insist on making out the opposite time and time again?
 
You must log in or register to reply here.


advertisement


Back
Top