Question about S-video

[GM]

Hi all,
What if any are the limitations on driving more than one
appliance - for instance a TV and a DVD recorder from the one S-Video
output simultaneously ?

regards
Giles

 

On Thu, 1 Apr 2004 21:01:11 +1000, "GM"
<n0_SPamhathill2000@yahoo.com.au> wrote:

Hi all,
What if any are the limitations on driving more than one
appliance - for instance a TV and a DVD recorder from the one S-Video
output simultaneously ?

Yeah, each input loads down the output even more.

For a normal setup it's 2 volts out and then 2x75ohm resistors in
series making a voltage divider. 1Volt across each resistor.
1 is in the output side, the other is accross the input side.

When you add a second input device you still have the 2volts out, but
then you have 75ohm and 32.5ohm. Whacks up the voltages.

Some gear has a High Z / 75 Ohm switch on them, which lets you connect
it without it without interference.

 

[GM]

Thanks David,
Can I use a dual opamp to buffer the output and drive
two outputs - What frequency range would it need to cover etc ?

Giles



<David Sauer> wrote in message
news:3lvn60p1a49lih94ko8on0lq8outofc90i@4ax.com...

On Thu, 1 Apr 2004 21:01:11 +1000, "GM"
n0_SPamhathill2000@yahoo.com.au> wrote:

Hi all,
What if any are the limitations on driving more than one
appliance - for instance a TV and a DVD recorder from the one S-Video
output simultaneously ?

Yeah, each input loads down the output even more.

For a normal setup it's 2 volts out and then 2x75ohm resistors in
series making a voltage divider. 1Volt across each resistor.
1 is in the output side, the other is accross the input side.

When you add a second input device you still have the 2volts out, but
then you have 75ohm and 32.5ohm. Whacks up the voltages.

Some gear has a High Z / 75 Ohm switch on them, which lets you connect
it without it without interference.

 

[Phil Allison]

"GM" <n0_SPamhathill2000@yahoo.com.au>

Can I use a dual opamp to buffer the output and drive
two outputs - What frequency range would it need to cover etc ?

Giles

** Just chain the various S-Video items ( in - out - in - out ... ) -
like everyone else does.





............ Phil

 

[Wdino]

Sorry David Sauer but you are not correct with your resistors.
Any video source has a source resistance of 75 ohms. And any video load has
a termination resistance of 75 ohms.
But the result is the same. You cannot connect two video loads across a
video source. The lower termination resistance will give reflections on the
cable which will usually cause visible problems with the picture. And the
lower signal voltage will dim the picture.

Use a dual pole switch to switch from one to the other or a video buffer
amplifier. Ordinary op amps do not have a wide enough frequency response. If
you really need a simple buffer amplifier then do a Google search for "video
amplifier".

 

[Patrick Dunford]

GM

Hi all,
What if any are the limitations on driving more than one
appliance - for instance a TV and a DVD recorder from the one S-Video
output simultaneously ?

Probably the same as composite - signal loss with resulting quality /
brightness loss.

Get a distribution amp with multiple outlets if you can. There are some
kitset ones available, Altronics also sells some premade ones I think.