The RFI Problem

Part 1: Confusion

So many people are steered straight into RFI (radio frequency interference) problems by opportunist manufacturers, retailers and forum threads, that this topic is being written to try to redress the balance. Things have got that bad in hi-fi IMO that this post will look like I'm swimming against the tide. The fact is that the tide has been artificially manipulated to look like that - real science hasn't changed, but pretend science has reared it's ugly head disguised as the truth, looking all so cool and kinky.

Improper practices in cable or interconnect construction are being touted as being correct practice to such an extent that people like me as well as the Radio Communications Agency (Ofcom) and even Nasa in the USA look like we're the liars!

Sorry, physics aint changed!

It's still the same, but so many have jumped on the bandwagon - many a reviewer too, that it looks like a new science has been discovered.

Actually it's a new kind of witchcraft based on old ideas of how to wire audio while at the same time, the air all around us is getting saturated with a staggering amount of radio frequencies.

The witchcraft won't keep out the RFI, but digital audio sources don't expose the problem - so nobody sees the problem - until they get into vinyl!

Then, using interconnects that are "interference magnets" the equipment manufacturer not only gets the blame, but is expected to effect a cure.

Luckily so far, less than 50 customers out of nearly ten thousand over a 9 year stretch have had cause to complain. I know quite a few manufacturers wouldn't go to such lengths to help so few.

It may have only been less than 50 customers over nearly ten years, but the problem is now getting more frequent, so I want to have my say before it gets to tsunami proportions.

I have voiced my opinions on this subject in numerous places only to be shot down with words like "Who cares? So long as it makes music!" Unfortunately people who reply like that don't realise they've adopted the Lemming's attitude to life. But I'm supposed to catch them when they fall off the cliff.

There is one, and only one way of preventing RFI entering a system and that's by shielding (screening in UK English), I repeat SHIELDING. I'll say it again but louder...

SHIELDING!

However shielding isn't properly understood. There are however hundreds of proper references to correct shielding techniques all over the Internet, the problem is these references don't look cool. They don't spin like a politician so therefore they must be a load of rubbish. A guide to finding the truth is that when you've found it, it won't ultimately lead to a price sticker! It won't feature Flash animations or be adorned in gold and one inch thick onyx!

Shielding is simple - many of the best things in life are simple!

Unfortunately it takes hundreds of pages of scientific formula to prove it works where the opposite only takes a paragraph or two of complete drivel to get you hooked!

Because this topic cannot be properly addressed in a few lines of spin - it is a "major work", it will be continued each time I find I have the time. So this is the end of part one, and I will edit this post to add part two, three, etc, until I feel that I've done proper shielding justice and hopefully helped two or three people along the way.

Such is life.............

Part 2: KISS

Keep it sodding simple! And you will find things work better, especially when it comes to keeping the RFI "explosion" at bay.

When most of the ideas the snake oil peddlers are now peddling originated, the Radio spectrum was very much smaller and much less widespread. The snake oil peddlers don't understand science - they make up their own descriptive words, a bit like children do at playtime. For if they did understand science and the fact that the airwaves are now more overcrowded than ever, they'd realise that their un-shielded, or partially shielded  interconnects would let in large doses of RFI - poison for music!

Even if a radio station isn't detected the carrier frequency can cause distortions due to instability in amplifier circuits (instability caused by RFI). If your amp burns out for no particular reason you can think of, maybe it was being driven unstable by RFI? I guess that doesn't really matter if it's within the warranty period, but when it's out of that, you pay the bill! What goes around comes around, I think the saying goes?

But it does matter to any proper manufacturer dealing within the European Union or European Community where EMC law applies. Electro-magnetic-compatibilty (EMC) is about keeping RF out (immunity), or in (emissions control) depending on what you make.

There is only one particular practice for audio interconnects whether they be for audio equipment or radio equipment, and that is to FULLY SHIELD them. Anybody not doing that is actually in breach of the law when trying to sell such a thing in Europe (and that includes the UK).

Why they don't seem to know about this beggars belief! The law was introduced in 1996!

(and has since been updated, see this new directive!)

In fact, any EU based retailer selling an unshielded cable audio interconnect to a EU customer is also in breach of European law - ever heard of aiding and abetting?

The law only applies to merchandise (including kits) which lets off the hobbyist constructor as far as the CE directive is concerned, but even he/she could (would) be prosecuted if it resulted in some form of accident.

So KISS! Keep it sodding simple and ensure the interconnect is fully shielded, and manufacturers - it's so very easy to do - just use a shielded cable and connect the shield both ends.

Customers (having the right gear to start with) will marvel at how so much more music gets through! And wow! No radio!

In the next part I will take a deeper look at better ways of keeping RFI out so that your interconnects can stand the test of time (as the RF explosion gets bigger still).

Part 3: Single Ended Interconnects (Unbalanced!)

When quite a few years ago I learned of cables with the shield connected at only one end I wondered how the signal got through - "an open-circuit!" I exclaimed.

Silly me. They work just like the pick-up arm shield does. So this description covers both: There are both "signal" and "return" wires inside the cable (or arm), and the shield is the overall braid/foil (or the arms metal tube). The return and shield are joined one end so the shield (or arm tube) protects the "signal" conductor from interference. Or does it?

Remember, this convention came about at the dawning of the electric phonograph!

Yes, many of the boutique cables are "old hat"!

In todays radio-wave stuffed world, neither the pick-up arm or the single ended shield interconnect stand a chance of protecting the "signal" conductor from RFI!

So why hasn't anybody done anything about it? Don't ask me. All I can assume is they are blind, deaf and dumb when it comes to keeping up with technology.

But there is a movement toward everything being balanced. Why? Well, at least balanced audio "strips" a lot more interference because balanced inputs differentiate between what is signal and what is interference. So it shows that a clean signal is preferred by people even if they don't understand the technology behind it.

But you can have the same clean signal in a non-balanced hi-fi system!

Firstly, you'd need to forget about these single-end-shield interconnects and buy something that has the shield connected both ends, so the shield becomes the "return" which is the way convention was for interconnects before the boutiques started thinking they could copy balanced techniques in unbalanced systems.

Secondly, the tone arm manufacturers need to wake up to reality - I rewired a Hadcock arm (probably the most difficult arm to do this type of operation on) and the improvement was on equal par to that of a balanced phono stage, but without the expense.

You see, if the signal return current does not flow in the shield (and no current at all flows if the other end is left floating), RF interference easily enters. For a 1 metre interconnect wired one-ended, RF frequencies can get in at frequencies as low as 30MHz!

One-end shielded interconnects are good at low frequency shielding I must admit, so why do people complain of hum as well as radio interference? The answer is quite simple: The radio spectrum also features TV transmissions! Never thought of that? Well, how is the picture synched or framed? Yes, using a refresh or raster frequency which just happens to be in the 50 to 100 Hz region - and that's hum! Let it in at the interconnect at your peril: The raster information is amplitude modulated which means any input stage of any amp can easily "detect" it and then obviously reproduce the horrible sound of hum!

With a pick-up arm the problem is thankfully smaller. The arms length is shorter than the average interconnect's 1 metre. Therefore the RF interference is much higher in frequency - fewer transmissions to land on it by accident. But if you just happen to be close to a transmitter or number of transmitters, you will most likely have a big problem with RFI. If pick-up arms were to have the metal tube as the return path conductor, such interference would be vastly reduced or eliminated, but that requires a massive rethink by tone arm manufacturers.

When the great analogue switch-off of TV transmitters happens, the hum problem should go away, but does that mean the single ended shield idea will then be OK? No, there will still be radio interference, but of a digital nature, and my thoughts on what I'm now experiencing, is they lead to a very shrill sounding musical experience - not very pleasant at all, especially on headphones. It will be even more important to properly shield all interconnects, and something really needs to be done about pick-up arms.

When you consider this part 3 of my explanation, the penny should now drop regarding those totally un-shielded interconnects? And those interconnects that claim by twisting, that they are shielded. If a gap exists, RFI gets in. A twisted cable gives some RF attenuation, but probably only half of what bell wire does! I class people who make such interconnects as opportunists because 1] the product breaks the EMC laws (in Europe at least), 2] Being expensive they work on the principle that being expensive they must be better, 3] they cause other manufacturers a headache not of their own making, and 4] at the end of the day you've been duped (IMO)!



The above diagram shows 3 ways of making an interconnect...

a. The boutique twisted cable: Does not afford any shielding at all and will pick up RFI

b. The boutique single-ended-shield cable uses balanced audio twisted mic type cable or variants thereof: It provides shielding of low frequencies but becomes ineffective to RFI at 30MHz (1 metre length). Above this it will pick up many broadcast frequencies and is wide open to TV transmissions allowing the amplitude modulated framing frequency (50 - 100Hz) which is "hum" or "buzz" to be detected and amplified by the slowest junction in the system (who do you then blame?)

c. Conventional Coaxial: Shield connected at both ends, the return signal current flows in the shield and becomes a barrier for RFI at all frequencies. A single shield is effective in most cases, but in areas of strong radio waves, a double shield comprising >100% foil plus overall braid shield will be far superior.

Part 4: Spurious RFI Generators

Sources of RF pollution aren't just radio stations, TV channels or the local Taxi firms transmitter - they can be pieces of hi-fi equipment too!

Note the above distinction "hi-fi equipment": Equipment that is truly high fidelity could not cause any harm, but the abbreviation "hi-fi" stopped meaning high fidelity many years ago, and that's not just my opinion - it's a fact!

At one time I thought I had a serious problem. I kept having daft thoughts. I kept thinking that some hi-fi equipment was being made to produce distortion and RFI (EMC). But recently after taking on some repair work for a series of "manufacturers" as a trial run from a business point of view, I now realise these were not daft thoughts at all.

To be perfectly honest I am shocked with what I have seen: Amplifiers operating on the edge of stability with no output inductors to prevent them radiating spurious radio frequencies and a no-oversampling DAC that intentionally doesn't have sufficient output filtering to prevent the sampling frequency being radiated from its output - to name just two.

The spurious RF will and does break through into the vinyl front-end - and it's not the vinyl front end's fault! Even if it's not heard as interference, it destroys the vinyl's musicality.

It would seem that unscrupulous western opportunists are cashing in on the "buy cheap in China - sell dear here" syndrome to get Chinese or ROC subcontractors to make these ill-conceived products. It's a waste of good materials and Chinese talent! It's also a waste of your money if you're unlucky to be taken for a ride with these products.

But how do you know which products to avoid? The sad truth is there's no easy way of telling. Think of it - the hi-fi world is full of small "specialist" manufacturers, they all look the same from the customers viewpoint - it's impossible in most cases to distinguish the good from the bad. Obviously that causes Graham Slee Projects Ltd a problem, not only on how we defend our products from spurious or broadcast RFI from external influences, but how we make the customer aware that we do things properly and aren't just another bandwagon business.

Once upon a time the distributor and dealer would ensure that misbehaving products never reached the shelves, but times have changed: In the UK for example, Engineering has become an unsupported subject politically (due to our governments preoccupation with the money markets) and has been heading that way for years. Not having the quantity (or quality) of Engineering talent we used to have, and with poor wages on offer, distribution companies and dealers are often bereft of engineering skills. Therefore most have no idea of what's right and what's wrong. Then there are the unscrupulous dealers who trade online: Some are kosher, but many aren't and wouldn't know the difference between a microwave and an oscilloscope! These unfortunately belong to the box-shifting bandwagon  - constantly on the look-out for attention grabbing products to sell you.

The best way of attention grabbing is to sell lots of big and heavy aluminium cases with stunning looks, and I will say, the products we were investigating for the repair business definitely fitted the bill. Some poor Chinese man or woman must have lavished great attention over making these beautiful cabinets only to have them filled with rubbish!

The non-technical customer who simply wants good music has my sympathy.

Faced with all the RF interference above it's a miracle in my opinion that the numbers of our products falling victim over the last 9 years still only numbers less than 50!

More info on phono preamplification at http://www.gspaudio.co.uk/phonopreampstage.htm







Edited by Graham Slee - 03 Mar 2008 at 5:15pm

The Goats who are the European Parliament, and other similar Goats around the world, just love to string you up and stress you out – it’s like a drug to them and they just keep wanting to do it more. Sadism is what keeps these Goats on a high. One of their sadistic fetishes is to not only destroy vinyl, but to bring it back to life to destroy it again and again and again – they are the true vandals – the prime vandals – and total assholes!

The Brits and Dutch pushed drugs in China in 1850 – now they spend copious resources trying to stop the kids doing it!

The EU are vandals to every known profession – and now vandalism in the streets is on the increase!

What goes around comes around!

Back to the point: Thanks to their “good intentions” circuits that worked great just a few years ago, don’t anymore. One of the reasons is the chemistry, the other is the proliferation of radio frequencies. Together they combine to wreck the sound. I did try warning people this would happen back in 2004, then again in 2005, then I gave up trying in 2006 when the EU legislation tidal wave started to become law.

My hands tied, I can only now continue to design ass kicking audio at a snail’s pace – every single design that worked sonically yesterday doesn’t today, unless you tweak it to a ridiculous extreme. And that’s how we continue to achieve our great sound, whereas others, going on individual reports from the Bristol Show and the like, have lost it.

One of the main reasons is the lack of Lead in protective coatings and in solders. Plumbum as it used to be called, came into existence because of the Romans – they used Lead pipes for drinking water for thousands of years, hence the word Plumbing! Obviously it was that bad that it wiped out the Romans? No! They just changed their name to Italians! And as the food adverts are always asking “what makes Italians live so long?” Well they survived thousands of years of Lead pipes! Yes, the advert goes on to say – it’s their diet!!!!!

Our modern diet is killing us, not the things we’ve had for thousands of years!

Anyway, back to the subject and Lead is used to line rooms where delicate radio frequency research is carried on – it effectively stops all interfering radio frequencies getting in!!!!!

Need I say more?

When I changed mit tonearm (from Linn Ekos to Dynavector DV 507) I recognized  some humming and RFI. Using the integrated phono preamp of my T+A amplifier there was no humming or "radio sounds". I was in doubt, if my new GSP phono pre equipment is the right stuff to stepup my Dynavector MC-cartridge. I saked Grahem to give me some advice. He told, that shielding is essential. So I have found a solution
to eliminate RFI and hummining:
I have realised a shielding according to the recommendation given by Graham and put
it around the tonearm cable. (dealer adress)

Hi,  I just received a Graham Slee Bridge phono stage from Origin LIve UK. I'm in New Zealand. I am suffering from the dreaded RFI.  I have a 9 year old marantz pm55 amp a 0.5 metre anticable interconnect and anticable speaker cables.  Whether I have my turntable plugged into the Bridge or not, whichever input on the amp the Bridge is plugged in to produces audible radio through both speakers.  I have tried a different interconnect (a standard shielded cable) but the problem remains.  If I power off the Bridge, the radio noise disappears. I don't have a tuner plugged in to the amp.  And as I mentioned above, it makes no difference whether the turntable is plugged in to the Bridge or not.  This is the first time I have had this problem in my setup.  Can you give me any advice on what I can do to eliminate the RFI?