| Video Noise April 2002
DIY Component-Video
Cable
Component-video connections are
definitely the hot ticket if you have equipment that uses them properly. However, some of
the early gear with component-video was merely the previous year’s model with an
extra connection. The key is to use the component-video signals as intended.
The most questionable devices converted the component-video
signal back to S-video or even composite, rather than preserving three discrete signals.
But as older models and chip sets have been replaced, especially with fully digital units,
component-video connections are almost always implemented as intended internally.
Question: What is the difference between a composite
cable, an S-video cable, and a set of component-video cables?
Answer: The number of cables involved, and the annoying
connectors on the S-video cable. Other than that, all the cables are essentially the same.
They have the same performance requirements, the same type of construction, and all pretty
much carry the video signal with decent quality.
Once you get past poor-quality video cable, all of them
start to look more and more similar. You may find that, unlike audio cables, most video
cables without restricted bandwidth produce similar images when used between DVD players,
video displays, surround processors, or A/V receivers. You may see minor differences, but
differences can almost always be tuned out using your display’s brightness, contrast,
tint, and color controls.
Two-thirds of a component-video cable set, nearly free
Snip the connectors off of an S-video cable you would
otherwise retire, and replace them with four 75-ohm RCA connectors and you’ve got
two-thirds of a new component-video cable set. You still need a third cable though. What
to use? How about that old composite cable you have in the closet? Or how about that
digital cable you don’t use anymore? They both will make a perfectly good leg of a
component-video cable set.
Put this other cable on the
"Y" connection (green) and use the other two cables from your S-video cable on
the Pr (or Cr) and Pb (or Cb) connections (red and blue).
Disclaimer: Some mini-coax used in S-video cables
can be very delicate to work with. If your S-video cable is very small in diameter, you
may find that stripping it or soldering it is almost impossible. Check the connections in
the S-video cable before destroying the cable by cutting the connectors off.
The right RCA connector
You can find cost-effective 75-ohm RCA connectors at www.partsexpress.com (part number
091-400, $4.25 per pair). I recommend soldering RCA connectors on video cables, not
crimping the connections.
There is a crimp-type RCA for coax though. If you
must use that connector, you should solder the connection after you crimp it.
After attaching the RCA connectors, I recommend treating
the ends of the cable near the solder connections with Caig Labs D5 DeOxIt 5% spray, which
is also available from Parts Express. This will preserve the condition of the wires, wick
down the wires as far as oxygen will ever travel, and will protect the wire near the ends
from oxidation. You can then put the DeOxIt spray on the male and female RCA connectors as
well, to protect them from base metals migrating through the porous gold plating.
Make the whole component cable set yourself
Don’t have any old composite or S-video cables and you
want to make the whole set(s) of component-video cables yourself? My recommendation is to
use the same 75-ohm RCA connectors referenced above and any of the Belden cables specified
for HDTV use. These cables are all 100% tested at frequencies up to 3GHz. It will be
easier to find cables with bandwidths up to 400MHz, but I think it’s worth going for
the higher-bandwidth HDTV coax. Belden 1865A appears to be the highest-performance
stranded coax available. You can search for HDTV-capable Belden cables at www.belden.com.
Cables with stranded and smaller-gauge center conductors
will be the most flexible. Belden quotes the signal-propagation speed as a percentage of
light speed (in the technical info for each cable). The stranded HDTV cables seem to top
out around 82%. The higher the number, the better.
Solid-core and larger-gauge center conductors will make for
stiffer cables. The diameter of the cable will also be some determinant on flexibility.
Thick cables with solid center conductors will be stiffest, while small-diameter cables
with stranded center conductors will be the most flexible.
The problem with Belden cables is buying 25’ at a time
-- enough for a single 8’ set of component-video cables. The price of the cable is
such that you can buy 500’ of cable for under $100, even with the high performance
required for HDTV bandwidth. But what are you going to do with 500’ of cable? Sounds
like it may be worth arranging a group buy where five people share a 500’ spool. Shop
carefully for the cable, though. I’ve seen prices as high as $250 and as low as $75
for the same cable in the same 500’ lengths.
On the other hand, you’d be surprised at how fast you
can go through cable when you are connecting a whole system using component-video cables.
Let’s say you need 10’ cables and you are going to connect your satellite
receiver and DVD player to your surround processor or A/V receiver. Then you connect the
processor or A/V receiver to the video display. That’s three sets of cables with
three wires in each set. That’s already 90’ of cable! Suddenly the 500’
spool of cable doesn’t look that scary!
...Doug Blackburn
db@hometheatersound.com |
