| Author |
Message |
Gerard Bok
Guest
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 Posted:
Wed Jul 27, 2005 4:20 pm Post subject:
Re: connecting PC to TV |
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On Wed, 27 Jul 2005 07:57:01 -0400, James Knott
<james.knott@rogers.com> wrote:
| Quote: | Gerard Bok wrote:
Actually, I doubt that.
On audio frequencies and levels, a 'simple balun' requires a
complete mu-metal encased transformer.
Otherwise, just the transformers themself both would pick up as
much noise as the twisted pair suppresses :-)
And this arrangement would still suffer from rather huge losses,
both in level and sound quality. My 2 cents :-)
It's entirely possible to build a transformerless "balun" with op-amps, that
are configured to convert balanced to unbalanced and reverse. They can
also provide gain and have a frequency response going down to DC. Anyone
working with instrumentation would be familiar with such applications.
|
I initially figured that the device was such a beast.
But http://www.svideo.com/svideobalun1.html points to a device
that is described as 'passive' and does not require any power.
Have yet to find a chipset to cover that specs :-)
Some practical experiments I made after my posting show, that
twisted pair performs remarkably well, even on unbalanced sound.
And more astonishing, composite video over 25 feet of twisted
pair shows no visual degradation despite the lack of balancing
and proper impedance matching.
Guess I'm learning. Every day, still :-)
--
Kind regards,
Gerard Bok |
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James Knott
Guest
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| Posted:
Wed Jul 27, 2005 4:20 pm Post subject:
Re: connecting PC to TV |
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Gerard Bok wrote:
| Quote: | And more astonishing, composite video over 25 feet of twisted
pair shows no visual degradation despite the lack of balancing
and proper impedance matching.
Guess I'm learning. Every day, still :-)
|
Twisted pairs have been used for many years, in a variety of applications,
because it does work so well and avoids the ground loop problems of
unbalanced shielded cables. |
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Gerard Bok
Guest
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| Posted:
Wed Jul 27, 2005 4:20 pm Post subject:
Re: connecting PC to TV |
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On Wed, 27 Jul 2005 09:17:01 -0400, James Knott
<james.knott@rogers.com> wrote:
| Quote: | Gerard Bok wrote:
And more astonishing, composite video over 25 feet of twisted
pair shows no visual degradation despite the lack of balancing
and proper impedance matching.
Guess I'm learning. Every day, still :-)
Twisted pairs have been used for many years, in a variety of applications,
because it does work so well and avoids the ground loop problems of
unbalanced shielded cables.
|
But even on unbalanced signals, it appears to perform very well.
Given the comments made by Dmitri I created a 25 ' SCART to SCART
connection, using twisted pair cable.
Violating almost all I 'know' about such connections:
- no shielding
- asymmetrical signal on symmetrical cable
- 110 ohms cable in a 75 ohms system
- There are 3 different ground connections in the cable
--
Kind regards,
Gerard Bok |
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Dmitri(Cabling-Design.com
Guest
|
| Posted:
Thu Jul 28, 2005 12:20 am Post subject:
Re: connecting PC to TV |
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Gerard Bok wrote:
| Quote: | I initially figured that the device was such a beast.
But http://www.svideo.com/svideobalun1.html points to a device
that is described as 'passive' and does not require any power.
Have yet to find a chipset to cover that specs :-)
|
Op amps would have probably worked similar or better in most cases, but,
simply because they require power (sometimes even two supplies, depending
on the actual part), it is much more practical to build a balun on a
transformer that's capable of working on frequencies your application
requires. It is actually the reason you need to have a wide variety of
baluns for every application, not just one model for any
asymmetrical-to-symmetrical situation.
One other thing to consider would be this: Op amp would probably be TOO
SENSITIVE for the task, and would amplify the noise as well as the useful
signal. That can be handled by filters, but the circuitry tends to grow
unnecessarily complex. With transformers some loss is actually healthy
'cause it filters out the noise.
--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
##-----------------------------------------------#
Article posted with Cabling-Design.com Newsgroup Archiv
http://www.cabling-design.com/forum
no-spam read and post WWW interface to your favorite newsgroup -
comp.dcom.cabling - 2209 messages and counting
##-----------------------------------------------## |
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James Knott
Guest
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| Posted:
Thu Jul 28, 2005 7:35 am Post subject:
Re: connecting PC to TV |
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Dmitri(Cabling-Design.com wrote:
| Quote: | One other thing to consider would be this: Op amp would probably be TOO
SENSITIVE for the task, and would amplify the noise as well as the useful
signal.
|
That would depend entirely on how you design the circuit. The nice thing
about op amps, is that it's very easy to set the gain and impedance to
whatever you want (within the capabilities of the device). If configured
for low or gain and input impedance, noise would not be a significant
problem. |
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Watson A.Name - \"Watt Su
Guest
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| Posted:
Sun Jul 31, 2005 12:20 am Post subject:
Re: connecting PC to TV |
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"Gerard Bok" <bok118@zonnet.nl> wrote in message
news:42e4bc0d.6779856@News.Individual.NET...
| Quote: | On Mon, 25 Jul 2005 07:00:50 +0000 (UTC),
techie@tantivy.tantivy.net (Bob Vaughan) wrote:
In article <42e3a399.4656982@News.Individual.NET>,
Gerard Bok <bok118@zonnet.nl> wrote:
On Sat, 23 Jul 2005 15:51:05 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
"Ed Nielsen" <egnlsn@comcast.net> wrote in message
news:iPSdnX3hyvwk5X_fRVn-gw@comcast.com...
Perkowski wrote:
JC wrote:
I have UTP cat 5 running all across my house.
Now I would like to play movies on my pc and transer the
signal to
my
TV over a UTP-cable..
Does anyone have any suggestions how I should be able to
manage
that
and what additional features are necessary to pull this off ?
Thx in advace
http://www.svideo.com/svideobalun1.html
Maybe?
Now you just have to worry about audio. If you had coax all over
the
house it would be a piece of cake.
There is no need for coax for audio. Better without coax.
Huh ?
Unless you either have a balanced driver / receiver with proper
twisted cable inbetween or you are transporting audio at speaker
levels, you will NEED some kind of coax :-)
(Or the sound on any program will be very boring: 60 Hz :-)
The links previously given are for baluns designed for the transport
of audio and video signals over category 5 twisted pair cabling.
A balun is a device designed to convert between balanced and
unbalanced
electrical signals, such as between coaxial cable and twin-lead.
Yes, thank you. I know what a balun is :-)
It is the 'better without coax' part that I don't understand.
Would a double balun with twisted-pair in between outperform a
straight coax connection on TV-audio ?
Actually, I doubt that.
On audio frequencies and levels, a 'simple balun' requires a
complete mu-metal encased transformer.
Otherwise, just the transformers themself both would pick up as
much noise as the twisted pair suppresses :-)
And this arrangement would still suffer from rather huge losses,
both in level and sound quality. My 2 cents :-)
|
Obviously the proof that you're wrong is that thing you pick up and talk
on every day, the telephone. It doesn't need mu metal shielding, and
the losses are not huge. THe bandwidth of telephone is limited because
the signals have to travel for miles over twisted pair. For a simple
in-house audio system with a few hundred feet of cable, the bandwidth
can be much wider than the audio system. This is how the audio pros do
it, over a 600 ohm balanced line.
| Quote: | --
Kind regards,
Gerard Bok |
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Gerard Bok
Guest
|
| Posted:
Sun Jul 31, 2005 4:20 pm Post subject:
Re: connecting PC to TV |
|
|
On Sat, 30 Jul 2005 16:17:29 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
| Quote: | "Gerard Bok" <bok118@zonnet.nl> wrote in message
news:42e4bc0d.6779856@News.Individual.NET...
On Mon, 25 Jul 2005 07:00:50 +0000 (UTC),
techie@tantivy.tantivy.net (Bob Vaughan) wrote:
In article <42e3a399.4656982@News.Individual.NET>,
Gerard Bok <bok118@zonnet.nl> wrote:
On Sat, 23 Jul 2005 15:51:05 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
"Ed Nielsen" <egnlsn@comcast.net> wrote in message
news:iPSdnX3hyvwk5X_fRVn-gw@comcast.com...
Perkowski wrote:
JC wrote:
I have UTP cat 5 running all across my house.
Now I would like to play movies on my pc and transer the
signal to my TV over a UTP-cable..
Does anyone have any suggestions how I should be able to
manage that
and what additional features are necessary to pull this off ?
..
http://www.svideo.com/svideobalun1.html
..
There is no need for coax for audio. Better without coax.
..
The links previously given are for baluns designed for the transport
of audio and video signals over category 5 twisted pair cabling.
....
On audio frequencies and levels, a 'simple balun' requires a
complete mu-metal encased transformer.
Otherwise, just the transformers themself both would pick up as
much noise as the twisted pair suppresses :-)
And this arrangement would still suffer from rather huge losses,
both in level and sound quality. My 2 cents :-)
Obviously the proof that you're wrong is that thing you pick up and talk
on every day, the telephone. It doesn't need mu metal shielding, and
the losses are not huge.
|
But there is an important difference :-)
Two actually. Your telephone system won't go far without power.
And most --if not all-- telephone lines apply amplification.
Both go missing in the passive balun system we were talking about
:-)
It is true that my assumption was wrong. But not for this reason.
I was expecting a balun to transform the kilo-ohms audio signal
into 110 ohms and back. Which, I still believe, would yield the
results I feared.
In practice, it is much simpler though. You don't need to match
the cable characteristics, at least not for audio.
| Quote: | This is how the audio pros do
it, over a 600 ohm balanced line.
|
Well, I know, I am learning every day :-)
But I have yet to meet a professional audio installation that
uses unshielded cable for it's 600 ohms balanced lines.
(Although in the mean time I learned that even simply replacing
coax with cat5 performs remarkably well.)
--
Kind regards,
Gerard Bok |
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James Knott
Guest
|
| Posted:
Sun Jul 31, 2005 4:20 pm Post subject:
Re: connecting PC to TV |
|
|
Gerard Bok wrote:
| Quote: | But there is an important difference :-)
Two actually. Your telephone system won't go far without power.
And most --if not all-- telephone lines apply amplification.
Both go missing in the passive balun system we were talking about
|
Back in the days before amplifiers, the furthest you could call, was from
about New York to Denver, so you don't need an amplifier to talk across
town. Also, it's entirely possible to pass DC power through a balun,
though it require appropriate split winding transformers and blocking
capacitors. |
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Watson A.Name - \"Watt Su
Guest
|
| Posted:
Sun Jul 31, 2005 9:45 pm Post subject:
Re: connecting PC to TV |
|
|
"Gerard Bok" <bok118@zonnet.nl> wrote in message
news:42ecaecd.787757@News.Individual.NET...
| Quote: | On Sat, 30 Jul 2005 16:17:29 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
"Gerard Bok" <bok118@zonnet.nl> wrote in message
news:42e4bc0d.6779856@News.Individual.NET...
On Mon, 25 Jul 2005 07:00:50 +0000 (UTC),
techie@tantivy.tantivy.net (Bob Vaughan) wrote:
In article <42e3a399.4656982@News.Individual.NET>,
Gerard Bok <bok118@zonnet.nl> wrote:
On Sat, 23 Jul 2005 15:51:05 -0700, "Watson A.Name - \"Watt Sun,
the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:
"Ed Nielsen" <egnlsn@comcast.net> wrote in message
news:iPSdnX3hyvwk5X_fRVn-gw@comcast.com...
Perkowski wrote:
JC wrote:
I have UTP cat 5 running all across my house.
Now I would like to play movies on my pc and transer the
signal to my TV over a UTP-cable..
Does anyone have any suggestions how I should be able to
manage that
and what additional features are necessary to pull this off
?
.
http://www.svideo.com/svideobalun1.html
.
There is no need for coax for audio. Better without coax.
.
The links previously given are for baluns designed for the
transport
of audio and video signals over category 5 twisted pair cabling.
...
On audio frequencies and levels, a 'simple balun' requires a
complete mu-metal encased transformer.
Otherwise, just the transformers themself both would pick up as
much noise as the twisted pair suppresses :-)
And this arrangement would still suffer from rather huge losses,
both in level and sound quality. My 2 cents :-)
Obviously the proof that you're wrong is that thing you pick up and
talk
on every day, the telephone. It doesn't need mu metal shielding, and
the losses are not huge.
But there is an important difference :-)
Two actually. Your telephone system won't go far without power.
|
That's _was_ an important difference. The telephone system wouldn't go
far without power, back a hundred years ago when there were no
amplifying devices, such as transistors or tubes. Nowadays, with
self-powered telephones (cordless, or any phone that runs off a wall
wart), or modems, faxes, etc, there is no need for power, other than for
signaling the condition of the line. So, wrong again.
| Quote: | And most --if not all-- telephone lines apply amplification.
Both go missing in the passive balun system we were talking about
:-)
|
That wasn't true a hundred years ago, and is becoming increasingly
unlikely nowadays, where the signal comes into the equipment and is
digitized by a codec. Again remember that most of the phone system was
designed a hundred years ago when there were no amplifiers, no tubes or
transistors.
| Quote: | It is true that my assumption was wrong. But not for this reason.
I was expecting a balun to transform the kilo-ohms audio signal
|
Generally, audio amplifiers have inputs that are in the kilohms, but
their outputs are usually much, much lower, in the hundreds of ohms.
They are usually capable of driving baluns that are, say, 600 ohms.
| Quote: | into 110 ohms and back. Which, I still believe, would yield the
results I feared.
In practice, it is much simpler though. You don't need to match
the cable characteristics, at least not for audio.
This is how the audio pros do
it, over a 600 ohm balanced line.
Well, I know, I am learning every day :-)
But I have yet to meet a professional audio installation that
uses unshielded cable for it's 600 ohms balanced lines.
(Although in the mean time I learned that even simply replacing
coax with cat5 performs remarkably well.)
|
For line levels you don't need shielding, but for mic levels, it best to
have the shielding to protect against that RFI and ENI that might leak
into the signal.
| Quote: | --
Kind regards,
Gerard Bok |
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