How do I connect 2 televisions to a PS3 for a charity singstar event!

In article , Ian Jackson wrote:
A scart y-lead would seem the obvious choice, unless I'm missing
something?

I guess you're missing the need for impedance matching.

Apart from getting 2/3 of the correct video level, what would be the
effect of double-terminating?

Reflections, the effects of which would depend on the lengths of the
various branches of the Y-cable.

Rod.
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"Mark Carver" wrote in message
...
Jon wrote:

A scart y-lead would seem the obvious choice, unless I'm missing
something?

You'd end up double terminating the PS2. Wouldn't do any damage, but you'd
get a dimmer picture than you should on both TVs. Might be good enough,
because you could adjust Brightness and Contrast to compensate, but it
would still be a bodge.

But compared to the singing it would be OK.

Bill

"Roderick Stewart" wrote in
message .myzen.co.uk...
In article , Ian Jackson wrote:
A scart y-lead would seem the obvious choice, unless I'm missing
something?

I guess you're missing the need for impedance matching.

Apart from getting 2/3 of the correct video level, what would be the
effect of double-terminating?

Reflections, the effects of which would depend on the lengths of the
various branches of the Y-cable.

A bit of echo can do wonders for karaoke.

Gentlemen, we need to take account of the customer's requirements. I
understand that this is for a display of the words for karaoke. If so the
signal source will be producing a very crude image, and the viewers will be
suffering significant amounts of alcohol induced perceptual distortion. I
would think the finer points of image quality are not an issue.

Bill

Bill Wright wrote:

A bit of echo can do wonders for karaoke.

Gentlemen, we need to take account of the customer's requirements. I
understand that this is for a display of the words for karaoke. If so the
signal source will be producing a very crude image, and the viewers will be
suffering significant amounts of alcohol induced perceptual distortion. I
would think the finer points of image quality are not an issue.

I know, I know; but here (in uk.tech.digital-tv) we like to strive for
technical excellence ;-). I can't speak for any bodgers in the other two
groups this is cross posted to.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

In message , Mark Carver
writes
Bill Wright wrote:

A bit of echo can do wonders for karaoke.
Gentlemen, we need to take account of the customer's requirements. I
understand that this is for a display of the words for karaoke. If so
the signal source will be producing a very crude image, and the
viewers will be suffering significant amounts of alcohol induced
perceptual distortion. I would think the finer points of image
quality are not an issue.

I know, I know; but here (in uk.tech.digital-tv) we like to strive for
technical excellence ;-). I can't speak for any bodgers in the other
two groups this is cross posted to.

But WILL there be a problem with reflections? Assuming everything is a
pretty good 75 ohms:

When the forward signal from the signal source arrives at the 2-way
split (which is only a T-connection), it will see an impedance of 37.5
ohms. This is an SWR of 2:1, or an RLR of 9.542dB.

The reflected power is (of course) -9.542dB, or x 0.111. This power gets
returned to the signal source, where it will be absorbed in its 75 ohm
output impedance, and no further reflection will take place.

As x 0.111 of the signal gets reflected from the T-split, x 0.889
(-0.511db) remains ongoing. This is shared by the two feeds to the TV
sets, so each gets half of 0.889, ie x 0.4445 of the power. This is
-3.522dB, which is x 0.667 as a voltage ratio. [Fortunately, this agrees
with my simple Ohms Law calculation for a 75 ohm signal source
(mis)-terminated by two 75 ohm loads in parallel.]

As the video signal travels to the TV sets in 75 ohm cables, there will
be no reflection when it meets the 75 ohm input of the either TV set.
There will therefore be no reflection from TV set to TV set.

So, provided you can increase the TV contrast and brightness to make up
for a video input of 0.667V instead of the expected 1V, it appears you
can get away with this 'botch'. But is it a botch? I reckon it is
adequately 'technically excellent' for all but the most demanding
occasions. As has been said, karaoke probably isn't one of them.
--
Ian

"Ian Jackson" wrote in message
...
But WILL there be a problem with reflections? Assuming everything is a
pretty good 75 ohms:

When the forward signal from the signal source arrives at the 2-way split
(which is only a T-connection), it will see an impedance of 37.5 ohms.
This is an SWR of 2:1, or an RLR of 9.542dB.
(and so on, but this gets me onto what I want to say)

There's a rather strange situation in this technical area in the CCTV world.
For ages recording devices of all sorts have had a 'loop thro' output socket
which have been used for feeding monitors or modulators. In effect the
device itself does not terminate the line but taps from it at a fairly high
impedence. If the line is to be terminated (the loop thro is not used) it
has been necessary to either fit a termination on the O/P socket or set the
device to 'lo Z' (this is done input by input) so the device terminates the
signal. However, many of the newer HDD recorders do not have loopthough.
This is often because there is now a craze for recording audio so the output
sockets are now used for audio in. The manufacturers say 'set it to hi Z and
use a T piece'. This works fine, as long as the line is actually terminated
by a good match to a modulator or monitor. I have used modulators where it
has been necessary to fit a 330ohm (or thereabouts) pot across the modulator
input and adjust for best picture on the HDD machine. So it seems that what
we are actually doing is taking the 75 ohm feed all the way to a termination
(by fair means or foul) at the modulator, with the HDD recorder input being
quite high impedence and actually acting as a tap-off. Furry muff, it works.

Bill

In article , Bill Wright wrote:
There's a rather strange situation in this technical area in the CCTV world.
For ages recording devices of all sorts have had a 'loop thro' output socket
which have been used for feeding monitors or modulators. In effect the
device itself does not terminate the line but taps from it at a fairly high
impedence. If the line is to be terminated (the loop thro is not used) it
has been necessary to either fit a termination on the O/P socket or set the
device to 'lo Z' (this is done input by input) so the device terminates the
signal. However, many of the newer HDD recorders do not have loopthough.
This is often because there is now a craze for recording audio so the output
sockets are now used for audio in. The manufacturers say 'set it to hi Z and
use a T piece'. This works fine, as long as the line is actually terminated
by a good match to a modulator or monitor. I have used modulators where it
has been necessary to fit a 330ohm (or thereabouts) pot across the modulator
input and adjust for best picture on the HDD machine. So it seems that what
we are actually doing is taking the 75 ohm feed all the way to a termination
(by fair means or foul) at the modulator, with the HDD recorder input being
quite high impedence and actually acting as a tap-off. Furry muff, it works.

It used to be common in broadcasting too for a video input to consist of two
adjacent BNC sockets connected together with a wire link behind the panel,
sometimes also wired to a switch next to them connecting a 75 Ohm resistor to
earth (to save the bother of finding a pluggable one).

Nowadays a lot of picture monitors still have the two sockets, but instead of
a mechanical switch some internal circuitry to detect automatically whether
that monitor is the one at the end of the cable, or an intermediate one, and
apply the terminating resistor automatically. I've never discovered exactly
what it detects, but as with any piece of electronics that attempts to replace
a bit of human thought, sometimes it can be fooled into making the wrong
decision, and of course anything that works can also become faulty. I think on
balance they create more confusion than they dispel.

Rod.
--
Virtual Access V6.3 free usenet/email software from
http://sourceforge.net/projects/virtual-access/

"Roderick Stewart" wrote in
message .myzen.co.uk...
Nowadays a lot of picture monitors still have the two sockets, but instead
of
a mechanical switch some internal circuitry to detect automatically
whether
that monitor is the one at the end of the cable, or an intermediate one,
and
apply the terminating resistor automatically. I've never discovered
exactly
what it detects, but as with any piece of electronics that attempts to
replace
a bit of human thought, sometimes it can be fooled into making the wrong
decision, and of course anything that works can also become faulty. I
think on
balance they create more confusion than they dispel.

Ah well, we installed some PCs which had the sole task of outputting
Powerpoint presentations to the RF distribution system. They had a video
card that would only send a composite signal out when it detected a load on
the output socket. Unfortunately they did not detect perfectly good loads
like the decent modulators we used, and as a result the option to output
composite was greyed out. 150ohm across the output solved it and didn't
bugger the picture up.

Bill

In article , Bill Wright wrote:
Ah well, we installed some PCs which had the sole task of outputting
Powerpoint presentations to the RF distribution system. They had a video
card that would only send a composite signal out when it detected a load on
the output socket. Unfortunately they did not detect perfectly good loads
like the decent modulators we used, and as a result the option to output
composite was greyed out. 150ohm across the output solved it and didn't
bugger the picture up.

That's the problem with electronics that tries to be clever. Sometimes it can
be too clever for another bit of clever electronics, with the result that
they're just too clever for each other and the combination of the two behaves
as if it were stupid. Thank goodness there's still a place for human
intelligence (whatever that is).

Rod.
--
Virtual Access V6.3 free usenet/email software from
http://sourceforge.net/projects/virtual-access/

"Roderick Stewart" wrote in
message .myzen.co.uk...
That's the problem with electronics that tries to be clever. Sometimes it
can
be too clever for another bit of clever electronics, with the result that
they're just too clever for each other and the combination of the two
behaves
as if it were stupid.

I went to a meeting a few weeks ago where the head honcho and his sidekick
were like that. They were so busy demonstrating to each other how clever
they were that they ended up making a really bad decision.

Bill