Installation manual

Page 9
MYTHS, MAGIC AND FACTS
Oh I forgot some facts about cables I would like to mention.
This applies really to home stereo. The typical RCA patchcord cable length from CD
player/Tuner to the pre amplifier is maybe 1.5 metres (4.8’). Even if the capacitance
between the inner conductor and shield is 350pF (Pico Farads) the CD player or tuner
has absolutely ZERO knowledge of this amount of capacitance. The same argument
applies to mobile systems where yes the RCA cables are maybe 5 metres (16’) in length
and typically we use a stronger construction type of cable in the vehicle, the inter-
conductor capacitance is again meaningless.
I measured a 6.5’ length of really cheap RCA-RCA cable and the capacitance was 500pF.
Example: The output impedance of the Head unit is say 1K ohm (On the high side in my
opinion) and together with the cable capacitance of 500pF forms a low pass filter with an
Fo (-3dB) of 318.471KHz! With a more typical output impedance of say 50 ohms this Fo
moves to 636.942KHz. So using a 5m (16’) decent quality well shielded RCA-RCA cable
from the Head to the amplifiers should not cause any high frequency roll off that you can
hear - unless you are a bat of course.
Here are two interesting takes on this issue.
Http://www.mmxpress.com/technical/interconnect_myths.htm
Http://www.audioholics.com/education/cables/skin-effect-relevance-in-speaker-cables
I read an interesting article from a guy “down under”. He makes some interesting claims
concerning cables one of them being that skin effect is audible. It is well known that skin
effect (the tendency of current to flow only on the outside surface of the cable) only occurs
at frequencies above about 100KHz. Now we are not bats (no I do not have a bat as a
pet) and no music gets to 100KHz so the cable companies push this %#@&* to sell to
unsuspecting consumers.
Semiconductors have more tolerance in their specifications than any capacitor or
resistor.
A well known fact is that different types of capacitors work better at certain jobs than
others.
Example, disc ceramic capacitors are better in high frequency compensation circuits
than film types. Film types work better in audio frequency selective circuits than ceramics.
So we at Zed choose our components to suit the application.
Finally this “fetish” that has been thrown around about low ESR 105C capacitors. If you
are looking for long lasting electrolytic capacitors then choose the hideously expensive
10,000 to 15,000 hour types. I have not seen a rational manufacturer using these in a
consumer product. To obtain low ESR (Equivalent Series Resistance) you can use a
single low ESR capacitor OR use a few “regular ESR” types in parallel, the result is the
same. Space restrictions force us to use low ESR types in many places but I have no
aversion to those regular old 85C electrolytic capacitors.