On Wed, 20 Aug 2003 17:02:10 GMT, "jason" wrote:

Maplin sell Digital Coaxial (Shark) which is claimed is "specifically
designed for digital audio interconnects such as those used between DVD
players and digital decoders for surround sound systems, it would be an
excellent alternative to regular 75 ohms coax where high signal quality is
essential", this cable however costs £1.99 per metre (and is out of stock!).
Is standard 75ohm low loss coax not suitable? Maplin do N12AP for £1.49 for
5metres which claims Nom. conductor areaf 0·786mm&square, and Capacitance
56pF/m, Attenuation per 10m:0·75dB at 100MHz, 2·6dB at 900MHz? Will this not
work OK?

I picked-up my new Maplin catalogue on Saturday.

"The cable core is 0.5mm diameter OFC Copper plated in 80um Silver.
The Silver plating takes advantage of a phenomenon of "skin effect".
"Skin effect" describes the tendency of ultrahigh frequencies to be
conducted on the surface of the wire as opposed to through the wire's
total profile. The lower resistivity of silver over copper ensures
optimum transmission of theses [sic] ultrahigh frequencies."
[Capitalisation as in the original.]

A quick calculation indicates the 24-bit 96kHz S/PDIF has a maximum
frequency about 10MHz - which being in the middle of the HF band is
way below UHF (ultrahigh frequency). The signal level is hundreds of
millivolts. How comes my television aerial down lead works when this
is running at around 800MHz over a some tens of metres with a signal
level of a few hundred microvolts and is analogue to boot?

Methinks this cable is snake oil and a complete waste of money.


--
Chris Isbell
Southampton
UK