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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: RFI & Interconnects posted by Lynn on May 13, 2006 at 19:26:42:
Hi.Just give an everyday example: Everybody gets one or more cellphones which all come with a tiny AC battery charger, which is switching mode power adaptor. A handy source of RFT when switched on to charge up the cellphone.
Too many example inside your home that emit RFI, including your PC monitor & LCD/Plasma flat panel TVs which all come with built-in switching mode power supplies.
How to suppress these noises which easily invade your audio gears
if placed too close. The most vulnerable RFI targets are power cords, ICs & speaker cables which are exposed without proper field shielding.Any conductors are handy RF receiving antennae. Period. The electrical wires looping around inside the walls, above the ceiling voids & underneath the flooring voids are excellent RFI receiving antennae.
When your digital equipment, e.g PC, flatpanel TVs, cellphones chargers, even simple as your CD & DVD players plugged into the wall AC power outlets, RFI are conveniently injected by conduction as well by radiation, into the whole power line loop inside your residence.
Without any EMI/RFI line filter in the power lines which power your audio gears means an open-house invitation of those EMI/RFI noises to your music.
I measured quantitatively how serious the wall AC oullet can be contaminated by using a brandnaem wideband powerline & EMI noise analyser. It is serious enough to call for something done.
Hence I built dedicated power lines direct from my house fuse panel
to power my audio/video gears, complete with fully insulated dedicated earthing wire direct to the earthing point of the fuse panel. Needless to say, I've added DIY power line filters right at the power outlet strips exclusively dedicated for both analogue, e.g. turntable, amps, & digital equipment, e.g. CD & DVD-audio players.But this is NOT the end of the RFI battle. The exposed power cords & interconnects are still the target of airborne RFI. Shield them all?
This is so involving (into the inside of all the audio components)& are they really that effective after all these involving hard work???
If your equipment is still under manufacturer's limited warranty, you can do nothing as any alternation will surely void the warranty.What is the easy & effective way of EMI/RFI suppression on the cords?
I did some field study to find out how the brandname audio/video manufacturers safeguard their interconnects, power cords, CATV cords,
speaker cords & PC monitor cords from RFI. They all come up with the same solution: snap-on or moulded on EMI/RFI ferrite suppressors.
One well-known brandname LCD TV maker even supply TVs with the 1-m power cord & PC monitor cord, each got one ferrite suppressor moulded on each end of the cord !!!!!One well-known brandname ICs makers supply its flagship audio & video cords with similar moulded-on ferrite suppressors.
Here you go. Let's borrow the profesional experience of those brandname makers. By adding such snap-on EMI/RFI fertite broad rings on the power cords, interconnects, destructive alternation by putting the external shieldng jackets on the cords can be avoided.
These ferrite rings are cheaply available from your local electronics supplies.I have read reports on such snap-on ferrite rings do improve the sound of the equipment bigtime: removing the haziness & restore the crystal clarity of the sound, improving overall definition, etc etc.
as result of stopping EMI/RFI going into the equipment via the cords.Of course, there is valid technical ground for this. Not aural deception as many objectionists challenged.
To make it very simple, the impedance of free space to EM field is 377-ohm. An antenna, receiving or transmitting, is a device to match such impedance of the related frequencies in the EM field. Adding
a ferrite ring on the cord simply serves to dismatch as much as possible.However, such suppressors with different ferrite core diameters get
different imepedance at different frequencies. For the reference RF of 100MHz, with pretty wide range of impedances, from 150R to 247R, etc. Also, where to clamp it on along the cord is another interesting experience. Try & error to get the best sonic result.c-J
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Follow Ups
- We got to fix RFI which is everywhere. (loooong) - cheap-Jack 12:31:25 05/15/06 (0)
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