Distributing Line Level Audio and Video over Cat 5?
Jim Sokoloff
Is it possible to distribute (cleanly) line level audio and video
signals (commonly on "RCA" jacks) over reasonable lengths (50 ft) of
Cat-5 cable?
Based on the fact that line-level cable exists (and is quite a bit
more expensive than Cat-5), I suspect the answer might be no, but I
thought I'd ask.
---Jim
Keith Doxey
Jim
It is easy to distribute line level audio and video over CAT5. We do it at
work over distances of upto 1300 ft with no problems.
To distribute audio all that is required is a dual op-amp at the transmit
end and a single op-amp at the recieve (per channel of course) to convert
from unbalanced to balanced signal and back.
To distribute video the same principles apply but the op-amps have to be
much higher quality because of the 6-8MHz bandwidth of the video signal.
Dedicated IC's exist for this purpose. Take a look at MAX435 & MAX436 data
sheets at Maxim http://www.maxim-ic.com
Also look at the Elantec site at www.elantec.com
I should have designs on my website soon,
keep an eye on it!
--
All the best
Keith
http://www.btinternet.com/~krazy.keith
The DIY Guide to Home Automation
Jim Sokoloff <soko...@tiac.net> wrote in article
<m1nu3dg...@fardm4.boston.deshaw.com>...
Dallas Dingle
If you convert to balanced line distribution at the distribution point and
then reconvert to balanced on the other end it would work. Audio Control is
advertising such a set up, It is cheaper to use shielded audio cable
unbalanced. Good Luck
Jim Sokoloff wrote in message ...
Keith Doxey
W. John Guineau wrote:
>
> What does "balanced" / "unbalanced" mean?
>
Unbalanced.
An unbalanced signal is the type you get out of your CD player
signal and ground.
Balanced.
a balanced signal is actually two active signals 180 degrees out of
phase with each other i.e. Differential. Each of the signals is of equal
magnitude to the unbalanced signal except that one is +ve and the other
is -ve. As ground is not used is is impossible to get a ground loop and
any interference picked up is equal on but signals. When fed into the
differential reciever (or transformer) the interference signal is
cancelled leaving a pure wanted signal.
HTH
Keith
Robert Connaghan
I hope you all don't think this is a shamless plug for my
companies products, but here are some things I use all the time.
Lucent makes adapters that can send video/stereo audio over Cat-5
twisted pair. They work great (unbiased opinion no doubt).
I use them to distribute video from a 64x64 VideoStereo Switch to
computers all around my facility. They don't require Cat-5.
This adapter is part of our Systimax Wiring system and
it is known as the #380A Video Adapter. They also have a six-port
distribution amp that works with the #380A adapter.
They aren't dirt cheap ($50+ each) but I thought you should know about
them. They allow you to run Cat-5 every where and then send video.
Here is a short list of the video modules available:
#380A: BaseBand (NTSC) Video and Stereo Audio over Twisted Pair
RJ-45 Jack on one side, BNC(1)/RCA(2) Jacks on the other.
#380B: BaseBand Video, with provision for Tilt/Pan/Zoom control.
It just uses one pair leaving three pair available
#384A: RF (Cable-TV) over Twisted Pair, up to 77 channels.
I really does work, I use it for a FM radio feed.
#381A: VGA RGB (640x480 at 72Hz) over Twisted Pair.
#383A: 6-port Video/Stereo Audio Distriburion Amp.
Don't forget to order the Power Supply!
Systimax is also promoting a new product line for the home, Homestar.
This is an integrated Video/Audio/Voice/Data distribution system with
home-run boxes and individual outlets. Looks Neat.
Contact:
Lucent Technologies, 800 344-0223
http://www.lucent.com/netsys/systimax/
http://www.lucent.com/netsys/homestar/index.html
Graybar 800-825-5517 carries them.
--
Robert Connaghan
Bell Labs - Multimedia Communication Research Department
r...@bell-labs.com
http://www.multimedia.bell-labs.com
This is not a Lucent Technologies corporate opinion, it's mine.
If it were corporate, I'd have to charge you for it.
Jim St. John
Robert Connaghan wrote in message <346C9B7F...@38.225.15.12>...
>I hope you all don't think this is a shamless plug for my
>companies products, but here are some things I use all the time.
>
>Lucent makes adapters that can send video/stereo audio over Cat-5
>twisted pair. They work great (unbiased opinion no doubt).
>I use them to distribute video from a 64x64 VideoStereo Switch to
>computers all around my facility. They don't require Cat-5.
>
How are they powered? Where can they be purchased?
-jim-
W. John Guineau
What does "balanced" / "unbalanced" mean?
john
David Alexander
"Jim Sokoloff" <soko...@tiac.net> wrote:
>Is it possible to distribute (cleanly) line level audio and video
>signals (commonly on "RCA" jacks) over reasonable lengths (50 ft) of
>Cat-5 cable?
If you get any good answers please post them. I'm preparing to run a
bunch of cat5 for line level audio and would like a little
reassurance!
FWIW, attached is an article I got off of Compuserve on building high
quality speaker cables. Several of the recipes call for cat5 cables.
It sort of validates the idea even if it is for speaker level instead
of line level...
============================================================
Speaker Cable Considerations and High Performance DIY Speaker
Cables from Commercial Wire
by Jon M. Risch
Goal: Perfect Transfer of Signal at Power Amp Output
Terminals to Input Terminals of Speaker
Conditions:
Very Low Output Z Voltage Source,
Output Voltages up to 100V,
Output Frequencies up to 21 kHz/70 kHz at close to full power,
8 ohm nominal load, 1.6 ohm dynamic load (or lower) with
reactive components at phase angles up to +/- 60 degrees.
Current up to ten's of amperes.
Minimum Performance Requirements:
Dynamic Range > 100 dB.
Simple Distortion < -80 dB.
Complex Distortion <-60 dB
(Preferably better, of course)
Important Design Considerations:
Minimum Resistance (less than 0.1 ohms for run to speaker)
Minimal Cable Inductance (try to keep to 2X resistance @ 20kHz,
this controlled through geometry)
Use Least Distorting Materials (bare copper/silver free from
oxidation and a dielectric with minimal capacitance abberations
and the most linear capacitance.
Maintain Physical Geometry under signal conditions (minimum
"magnetostrictive effect" or motor action between hot and ground
strands causing motion and induced EMF's)
Long Term Stability(lack of oxidation/corrosion effects)
Relatively Unimportant Design Considerations:
Capacitance (under 0.1 uF to avoid modern amplifier instability)
Overall Impedance or load matching (a cable Z of 8 ohms)
Appearance/Handling/Cosmetics (obviously, a retail product has
to worry about those things!)
Specifics:
Tinned conductors: The question has been raised, why bother with
bare copper if the components inside an amplifier, etc. are
constructed with tinned leads, etc?
My take on this is to consider that the speaker cable carries the
most current of any single component for the longest distance
(anywhere from 10 feet up to 30-50 feet as needed), so that any
effects due to surface "contaminants" would be at a maximum.
I consider "tinning", nickel plating, silver plating, or any other
material on the surface of the conductor to be a contaminant.
How is a tinned conductor a contaminated surface? Pure metals
have a crystalline internal organization molecularly, this is
basic metallurgy. Platings or coatings do not get applied in a
manner so as to totally avoid disrupting the surface of the base
metal. And the plating/coating itself is highly disordered, with
a large region where the two metals are mixed haphazardly,
severely disrupting the normal crystalline structure of both
materials. Any plating or worse, a coating, further disorders
the copper/silver metals crystal structure at the surface,
making worse whatever disorganization is already present due to
wire drawing, extrusion into an insulator, bending, etc.
The skin effect/self-inductance pushes the current flow out
towards the surface. Skin depth is defined as the depth at
which the current flow is down to 37% of the total. But the
distribution of the other 63% of the current flow is not
linear in distribution towards the surface of the conductor.
It is heavily skewed toward the outermost layer of conductive
material, with a very high proportion of that 63% of the
current, estimated at greater than 90%, forced toward the
very outermost surface. Hence the surface purity/linearity
of the conductor becomes important to passing a low distortion
signal, especially at high frequencies where the skin effect/
self inductance comes into play even more.
Geometry, Inductance and Surface Coatings:
The inductive reactance in a typical zip cord wire causes the
AC resistance to begin to rise above the baseline DCR level
somewhere in the midrange, usually by 1 to 3 kHz. It is at this
point that the self-inductance/skin-effect comes into play and
causes not only the cables effective resistance at this frequency
to rise, but the forcing of most of the current towards the
surface of the conductor. This action of often overlooked.
It is implicit in the relationship between the inductance of the
cable vs. the DCR of the cable.
Low-inductance cable designs not only minimize the variation in
frequency response due to amp/cable interaction with the speaker
system impedance, but helps reduce any dielectric nonlinearity
effects. Inductance by itself shows up as a direct effect in
the frequency response, these material problems are secondary,
and would manifest in low-level nonlinearities.
Magnetostrictive or Motor Effects:
The common reference to magnetostriction uses the term incorrectly,
as true magnetostriction would have the conductor itself changing
dimensions. This is not the case to any degree. What does occur
is movement of the conductors relative to one another due to peak
current flow, and the induced back EMF due to the motion while
carrying current. This is one reason soft insulator/spacer
materials should be avoided, stiff dielectrics like teflon or
polypropylene or even polyethylene will allow less movement and
reduce any magnetostrictive/motor effects.
My first introduction to this effect was with a pair of the old
Discwasher Smoglifters, a very loosely braided cable that would
show a pulse of motion with amplifier turn-on thumps.
A simple demonstration of the presence of this effect is to take
a loop of thin limp wire several feet long, lay the wire out in a
long skinny "U", with the spacing about 1/2" and pulse some
current through it (a car battery or such), with the usual
precautions and disclaimers, i.e., don't put the wire in your
pants and do this, always wear safety glasses, and have a fire
extinguisher handy. A pulse of current should cause the wires
to twitch or move noticably.
Vinyl Insulation (dielectric) Concerns:
Vinyl as an insulator/dielectric has a high dielectric constant
and a large amount of dielectric absorption. While the dominant
action of concern in a speaker cable is the current flow, and
related inductive effects, there is still a fairly high voltage
present too, one of the highest in the system (unless the
power amp is a tube amp). This voltage can be corrupted by the
delayed discharge involved with dielectric absorption.
A simple demonstration of D.A. can be had with a hand full of
parts: a power supply (could be a battery), an electrolytic
capacitor of several hundred uF, a pair of (alligator) clip leads,
and a high impedance voltmeter. If you don't own these or know
anyone who does, you could probably talk the local Radio Shack
counter dude into a demo with store parts. Charge the
electrolytic capacitor up with the power source (observe proper
polarity and stay within the voltage rating of the cap, easy if
your using a 9V battery) and then remove the source. Measure the
voltage stored on the cap with the voltmeter. It should be close
to the voltage of the power supply/battery. Now discharge the cap
with one of the test leads, holding the wire on the cap terminals
for a good couple of seconds, while the voltmeter is still
connected . The cap will have been completely discharged to some
extremely small voltage, perhaps 0.001 volt. After removing the
shorting wire, watch the voltage reading. Not only will it start
rising in spite of the load from the voltmeter, but it should rise
to an appreciable % of the original applied voltage, if 9 volts,
it could ultimately reach a volt with some caps. Now that's
distortion, something for nothing.
Most electrolytic caps have at least several % D.A., some even
higher. Vinyl has so many different formulations, that it is
difficult to even state a range, but generally in the one to
several % region.
Summary
My ideal speaker cable would have low series resistance across the
entire audio band in order to minimize the variation in frequency
response due to the amplifier/speaker cable impedance interactions
with the speaker impedance. This would be achieved by utilizing
any one of a number of low-inductance geometries with a sufficient
equivalent AWG.
It would have the most linear materials available in terms of
conductors and insulators, in order to avoid any materials related
non-linearities.
It would have the rigidity to minimize self-motor action
"magnetostriction", to avoid any potential for generating it's own
motion related distortions.
And it would have the proper material formulations to avoid long
term degradation effects from reducing the performance over time.
High Performance DIY Speaker Cables from Commercial Wire:
It is possible to obtain high-end speaker cable performance
from commercially available wires/cables. The information for
these home-made cable recipes was obtained through subjective
listening tests, and is based in part on earlier work done on
line-level interconnects. Materials used in the recommended
wires/cables are of the highest quality with regard to conveying
an audio signal. Some people may feel that the cables presented
here are wild overkill, I feel that they are barely adequate.
You have been warned!
Cable #1 - Highest Audio Performance
This is a difficult cable to assemble/solder, it is extremely
stiff, and the cost is somewhat high (minimum costs approx. $180
for two 24 ft. lengths, or approx. $3.75/ft). But it sounds great,
and could be a contender against ANY retail high-end cable at any
price!
This is a cross-connected dual-coaxial cable with foamed/solid
Teflon insulation, and bare copper conductors, using heat shrink
tubing with an inner layer of adhesive to bind the two individual
coaxes together. Cross-connecting a pair of side-by-side coaxial
cables involves electrically connecting the center conductor of
one cable (cable A) to the shield braid of the other cable
(cable B), and the center conductor of the other cable (cable B)
to the shield braid of the one cable (cable A) at both ends.
The coaxial cable used is Belden #89259, the heat shrink either
SPC Technologies type PHD-032 1/2" adhesive-lined polyolefin shrink
tubing, or 3-M EPS-200 1/2" adhesive lined, flexible polyolefin heat
shrink tubing. The cable and heat shrink are available from
electronics distributors all across the country. Newark electronics
is a major nationwide distributor with a website:
http://www.newark.com
Costs run around $138 for a 100 foot spool of the 89259, cut in half
twice it allows up to a pair of approx. 24 foot speaker cables.
If you don't need all that length, cut the coaxial cables
appropriately shorter, and use the leftover 89259 for interconnects;
it makes very high quality line-level cables with a nice teflon/
gold-plated RCA plug. The heat shrink tubing runs around $44 for
just barely enough to do the job (a package of 5 four foot lengths,
for a total of 20 feet), and it might be worth it to get twice that.
Precise wiring instructions follow.
The coaxial cables are stripped back 2.5 inches of the
outer jacket, the braid combed and dressed to one side, and the
center conductor cut off for 1", and then stripped off for 1".
The entire center conductor from the sheild braid point is bent at
a right angle to then wrap the exposed center conductor wire around
the base of the adjacent cables braid. The adjacent cables entire
center conductor is then bent toward the base of the original
cables dressed out shield braid, and the exposed center conductor
wrapped around the dressed braid. Make sure that each
center/opposite braid pair of conductors does not touch or make
contact with the other pair. Dress out the leads and color code
one coax braid/cable to be the hot side with a slice of heat shrink
(1/4") or using a red marker pen. The two wrapped areas are now
soldered, using plenty of solder and heat. Solder quickly, so as
to not melt the inner insulation very much.
(My favorite solder is Kester "44" in the 63/37% ratio)
Now, before completing the other end of the composite dual coaxial
cable, slide as many of the sections of heat shrink tubing as you
decided to use over the unfinished end, and space out accordingly.
Pre-form the dual cables in the shape/layout you desire, making
gradual bends, no sharp sudden radical angles, and make sure you
have each bend covered with a piece of heat shrink (or two, as
needed). A minimum radius would be 8 inches, and let the cables
"slide" into a top-bottom configuration for bends made in the
horizontal plane & vice versa.
Once the cable has been pre-formed to the shape for it to connect
to your power amp, and run to the speakers, carefully melt the
heatshrink onto the cable pair, keeping the pair as close and
snug as possible all throught he length. Heat shrink should
cover at least 1/3 of the distance along the cables, and be at
every bend. With 3-4 inch length pieces, spaced every foot or so,
this will keep the cable pair from being able to move relative to
one another. This is important to reduce any possible magneto-
strictive (so-called) effects.
Once the cables have been heat shrinked together, the other end
can be similarly terminated, and be sure that the same coaxial
cable is coded at this end as the first end. Once completed,
check for shorts with an ohmeter.
Measured specifications: Equivalent to 10 Ga. wire, capacitance
per foot approx. 48 pF/ft. Due to the low capacitance, this is
excellent for longer speaker cable runs. The extrememly low
resistance and low capacitance do not come with a penalty of
high inductance, the inductance is fairly low (measurements of
inductance unavailable at this time).
Speaker Cable #2
Another option is Belden's Vari-Twist cables. They make a Teflon
insulated version, but unfortunately, it has silver plated copper
conductors. Now I find it to sound a bit bright or "silvery",
but many who have heard it liked it very much, as the brightness
is very clean and has no trace of harshness. Belden part #'s
8V28040/50/60 (40 wires, etc.), and they are expensive.
Measured parameters on these make them the lowest inductance (with
a very reasonable capacitance for the inductance) cables available,
every other pair has a reverse twist, and they are spaced apart on
the ribbon substrate. Again, all the tan "ground" wires would be
connected together, and all the colored wires connected together
for the "hot" lead.
Measured specs: 20 pair - 255 pF/ft., less than .009uH/ft,
equivalent to 15 Ga. wire in resistance.
25 pair - 318 pF/ft., less than .007 uH/ft, equiv. to 14 Ga. wire
in resistance, 30 pair - 382 pF/ft., less than .006 uH/ft, equiv.
to 13 1/2 Ga wire in resistance.
Note: This is available only directly from Belden on special order,
and there is a minimum and a long wait for it to be manufactured.
Approx. cost last time I checked: $7-10/ft. depending on # of pairs.
Speaker Cable #3
Another option is to utilize plenum type Category 4 or 5 computer
wiring. Readily available, and relatively inexpensive, this type
of wire comes in many different configurations. The main things to
look for are in these Category 4 & 5 cables are: FEP Teflon
insulation (plenum version), unshielded and bare copper conductors.
Excellent cost per foot for the performance.
The most common type has 4 pairs of 24 Ga. wires, when the hots and
grounds are paralled, the 4 pairs of wire equal a 18 Ga. single pair
of wires. Two pair cable is available, but I would not recommend
buying it for use, as the equivalent Ga. is only about 21 Ga., and
doubling or quadrupling up on it is not as tidy. Ok if you have a
spool laying around though and don't want to buy the 4 pair and up.
If you are going to buy it, this is the preferred part #:
Four pair 22 Ga. Belden #1557A, less resistance than 16 Ga. wire,
equivalent to 13 Ga. when doubled up (two four pair cables in
parallel). Runs approx. 72 pF/ft. for a single 4 pair channel,
and approx. 160 pF/ft for the double run heat shrunk together.
Four pair 24 Ga. Belden part #'s:
1457A or B, 1585A or B, 1661A, 1669A
Mainstream availability makes these easy to find. Double up for an
equivalent 15 Ga. wire, and a quadruple run is better than 13 Ga.
Eight pair 24 Ga. Belden #1573A, roughly equivalent to 15 Ga. wire,
a double run is better than 12 Ga. More convenient than two 4 pair
cables doubled up.
Twelve pair 24 Ga. Belden #1577A, roughly equivalent to 13 Ga.
Two pair 24 Ga. (if you have some laying around) Belden 1590A, 1657A
and 1665A.
Construction is straightforward, solder all the solid colored wires
together for ground, and solder all the striped wires together for
hot. If doubling up on a cable, it is recomended that adhesive style
heatshrink of the appropriate diameter be used to lash the two/four
cable sets together (remember the recommended heat shrink is a 2:1
shrink ratio, do not get too small of a diameter, or it could split
when shrunk). See construction details for Speaker Cable #1
re heatshrink usage.
Other than these, there are very few options for low-cost DIY high-
performance speaker wire. If the thought of soldering all those
connections is a put off, then my personal opinion is that Kimber
Kable has the best low-cost speaker wire with the most universal
application to a wide diversity of stereo systems.
WARNING! These cables all have higher capacitance than ordinary
zipcord, enough that some poorly designed amplifiers may oscillate
into these cables! Most all modern amplifiers should not have any
problems, but there may be some exceptions. Use at your own risk!
*********************************************************************
Copyright Jon M. Risch 1997, all rights reserved, except transmission
by USENET and like facilities granted. Any use or inclusion in print
or other media are specifically prohibited. The informational content
is not warrantied in any way or form, and any use of said content are
at the reader's own risk, the author shall not be held responsible in
any way for any damages or injuries arising from the content of this
post. Common safety practices are encouraged at all times. Do not
fold, spindle or mutilate.
*********************************************************************
David Alexander
d...@extremezone.com
Robert Munck
>Lucent makes adapters that can send video/stereo audio over Cat-5
>twisted pair. ...
> #380A: BaseBand (NTSC) Video and Stereo Audio over Twisted Pair
> RJ-45 Jack on one side, BNC(1)/RCA(2) Jacks on the other.
>...
> #383A: 6-port Video/Stereo Audio Distribution Amp.
> Don't forget to order the Power Supply!
So rather than spending about $400 for a stereo MTS
modulator to distribute the output of my DBS receiver,
I can put a 383A at the distribution panel, tape a
380A to the back of the five TV's we have and connect
its outputs to the TV's A/V inputs, and use an RJ-45
patch cord to connect the 380A to the nearest outlet?
What if I have more than 6 outlets in the house? Can
I fan-out the 383A outputs to two drops each? If I
do, what happens if I (accidentally) have TV's
plugged into both of them simultaneously? It
probably would be acceptable to wire the 383A to
just six outlets and have to switch some wires in
the wiring closet to supply a signal to a different
outlet.
I actually have 3-6 stereo A/V sources in the wiring
closet (DBS, PC, VCR, someday a 1000-disk changer
with multiple CD/CD-ROM/DVD players). I suppose that
I could use a JVC SV-700 7x4 switcher with 380A's
on the four outputs and patch the 380A signals to
the outlets where there are TVs.
What I'd really like is a 8x8 or 8x16 switch matrix
for the 380A signals so that I could have up to 8
inputs and 8 or 16 outlets where I can plug in
380A-equipped receivers. Is that possible for
a reasonable amount of money, say $500?
Bob Munck
Mill Creek Systems LC
Brian Rudy
Jim Sokoloff wrote:
> Is it possible to distribute (cleanly) line level audio and video
> signals (commonly on "RCA" jacks) over reasonable lengths (50 ft) of
> Cat-5 cable?
Yes, there are several commercial solutions for doing this. One I have
experience with is Lucent's 380A, which has stereo audio, and video. It
is spec'ed for use with Lucent's Systemax and Gigaspeed, cabling
products.
I have seen other products for standard Cat-V cable in DataComm
Warehouse.
Good luck!
--
--------------------------------------------------------------
Brian Rudy
Sr. Exhibit Technician
The Tech Museum of Innovation
Phone:(408) 279-7139 FAX:(408) 279-7167
http://www.thetech.org
--------------------------------------------------------------