Ferrite on audio leads passing near PC?

Oh it contains ferrite ok. Its job to stop emissions coming *out* of the apparatus.

Graham

Er, not quite ! You commonly see them on leads coming from equipment that uses HF energy, like switch mode PSU's, CRT monitors etc. They are they to suppress any leakage of that HF energy via the connecting cable.

If you look carefully most of these leads are of the Co-Axial variety and the energy that is being suppressed is carried on the outside of the screen. Signals flowing on the inside of the screen are un-affected.

Yup. For _whole systems_, CE is a labelling thing of little concern to consumer end users, and rules are openly ignored in the light of history that there really hasn't been a successful string of prosecutions in the UK on EMC rule compliance for PC assemblers, for a long time, if ever.

For commercial use in business, and supply of component assemblies made for eventual construction of systems for end users, EMC certifications and compliance are more found important and are often demanded in purchasing and import orders together with all the other legal safety stuff.

However the testing (and passes) of assemblies may be specific to a certain (and sometime fraudulent) system configuration available at the moment, which may not be all that relevent to the final users use!

Some read CE as 'Chinese Export' and take no further interest in independant verification of these tests ...

I quit that job a long time ago now, thankfully. ;-)

No, CE means Can't Enforce.

John

Oh so true. At least half the equipment I see doesn't even have the Logo proportioned correctly despite the design being readily available online and easy to understand. Typically the C and E are too close together.

Graham

Graham

Hi Baron. I have had these "blobbed leads" supplied with:

(1) two MP3 players (2) two (flash-based) dictation machines. (3) a digital camera

If I've understood the info given in this thread correctly then I can't see what these players could be sending up their USB cable to require a ferrite ring. I believe a USB port under XP polls at 125 MHz and can go up to 1000 MHz but why does an MP3 player need this ferrite and my externally attached hard drive or printer not need it.

Is it just chance that my MP3 players & camera have had a ferrite on their lead or do other MP3 players also come with a ferrite on their supplied USB lead?

We once had a mini tower PC case in for test, the rather cheap tin sheet case was 'CE marked' by having the logo design enlarged and heavily embossed over the area where the motherboard fitted and almost covered it!

A con basically, a retailer could possibly advertise it as 'CE marked' and get away with the descriptions act.

It was an EMC failure in other respects if I remember correctly (in that ye couldn't build a passible PC system with it, RF emissions and ESD, mains conducted and RF immunity mostly hopeless)

No-one would use a ferrite if it wasn't needed ( it costs extra ). It's often there as a 'quick fix' for equipment that initally failed EMI certification. Some may fit one as a 'just in case' measure.

Graham

I found this. It accords exactly with what I've seen on some cheap imports.

Graham

Graham is right ! If it wasn't needed it would be there.

However all the Items that have been mentioned have in them one or more sources of high frequency energy that can and does leak out, usually via a connecting cable.

Don wrote in news:9BDE3A90BFAA15D4AM2@69.16.185.247:

As others said, improper shielding and suppression, but also, bear in mind that a low clock rate can still cause a lot of RF interference if the edge transitions are fast enough. Some components might have very fast rise/fall times, even in equipment where it's not required, if it turned out cheaper that way for whatever reason. It's usually cheaper to overspecify for bulk buying if the economy is good, than it is to agonise for a long time to select parts exactly, as the weakest link in the chain is what needs consideration most. So if a design works right, but some parts work at higher speeds than others, they won't cause failure, but might cause more switching noise. Despite the cost of a ferrite slug, it might be seen as the cheap way out.

YOU ARE AN IDIOT

I AM PROTEUS

You obviously know nothing about shielding or emission standards.

On 4/3/2009 12:10 AM Archimedes' Lever spake thus:

You obviously replied to a troll. You lose.

Your capacity to make a valid assessment rests at nil. You're a goddamned idiot.

Yeah, a troll knows all about being an idiot.......

Look, folks! He is finally going off the deep end! Oh wait... he has already done that!

Hahahahaha!