Laptop to TV and Sound

11 Jun 2006
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United Kingdom
I want to put a floor box in that will allow a laptop to connect to a TV at the other end of the room that will act as a monitor. I want picture and sound and be able to cater for a variety of laptops. My intention is to run HDMI cable but was also considering a VGA cable. However I believe there are adapters that will convert VGA or maybe DVI to HDMI and so I would just need HDMI. Is this true. Also how would sound get transmitted if VGA and DVI dont carry it. Laptops have a minimum of connections and don't always have DVI.

Any help appreciated.
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You can't convert VGA to HDMI with cable only. One signal is analogue, the other is digital. There has to be a box of electronics to make the signal conversion.

DVI is a connector that can be analogue or digital or dual format depending on the configuration of the device.

DVI-A is the Analogue only version. This can be connected to VGA with a simple cable or adapter. [DVI-A is very rare.]

DVD-D is the Digital only version. This can be connected to HDMI with a simple cable or adapter.

DVI-I is the Integrated version - wired for both digital and analogue.

If your floor box has VGA and HDMI then you have analogue and digital covered. If the laptop has a DVI-D or DVI-I output then you can use an adapter + HDMI cable for the digital connection. If the laptop has a VGA connection then you simply use the VGA to VGA cable.

I would also recommend adding a VGA line driver amp under the floor. Laptops are OK to run VGA down a 2m~3m cable if it is good quality wire. But for longer connections cables the signal from the laptop VGA port may not be good enough to avoid problems with ghosting and fuzzy text. 3m might be the length to wire from the laptop to the floor box, so you are already at the maximum before the connection from the box to the TV. A line driver amp boosts the VGA signal to overcome this problem.

Final point - Check what VGA signals your TV can accept and display properly. You may find that it is limited to certain resolutions.

For sound you need an extra connection. 3.5mm jack socket. Wire this to the PC audio input on the TV.
Thabks that is rely useful. Do you have an example of a reasonable line driver amp. The VGA cable will be about 5m
New - Kramer VP-111

Used - on Ebay - Extron RGB160xi

Both have high enough bandwidth (300MHz+) to cope with virtually anything you'll throw at them. e.g. 1080p/60Hz needs 186MHz, 1280x1024 @ 60Hz needs 118MHz. The Kramer is a bit more money but does use standard VGA connectors so off the shelf cables will work. Do buy decent cable though. Cheap rubbish will throw away the benefits of a line driver.

The Extron is older and the output is on BNCs but it's still a very good bit of kit. Extron was the product of choice for professional installs. I still use Extron gear for my hire stock, and that adapter would have been £200 ~ £300 back in the day.

If you're wondering what makes a good cable from a bad one here's a couple of pointers... You want something fairly thick (good shielding) with a bandwidth of at least 250MHz and the BNC connectors should be rated at 75 Ohms.

Mark Grant does some Belden Belden which is up to the spec. I use the Kramer equivalent which is a little more flexible and I add the shorter 75 Ohm BNCs which I find make cable routing a bit easier when it's in a confined space. Van Damme mini coax isn't as good (180MHz max bandwidth) but it'll still be better than the off-the-shelf moulded cables available on t'interweb.

If you've found this info useful and you'd like to show your appreciation then I can supply you with hi-res Kramer presentation cable made up with VGA or BNC connectors at a decent price. Like you I'm also in Cheshire.
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Why not just connect to tv locally [stick the laptop under the tv] and use wireless keyboard and mouse?
ChrisFrost - Thanks again.

Just one more question - I assume the line driver has to be located at the PC end of the cable run?
No, the line driver is located as close to the source end of the cable as possible.

In your case it would be in the void somewhere near the floor box...

LAPTOP-->--(connecting cable)--->---FLOORBOX + LINE DRIVER--->--(5m connecting cable)--->---TV

The problem with laptop VGA signals is that they're low power. It's a weak signal to start with. Pushing a weak signal through connectors and cable introduces additional losses. A weak signal gets weaker. It needs a boost before it travels any sort of distance. i.e. before the losses become too great. Boosting at the TV end is too late to repair the damage. That's why it's called a Line Driver - you're Driving (boosting) the signal down the Line which is the connecting cable. :)
Yes so I think that is what I said - at the PC end not the TV end - just checking.

Thanks again.
I have a similar setup. 5m VGA cable and a 5m 3.5 minijack to minijack cable plugged into an input on tv. Some tvs will require a phono connection. No problems at all and cables cost £6 all in from eBay.
For this kind of setup mine is a bit different

I have a MIDI TOWER to the left of my TV sitting on the floor with the VGA cable chased into the wall, all I have plugged into this PC is VGA POWER and NETWORK, nearly forgot JACKS for my 5.1

I also have a laptop connected to my WIRELESS network and using VNC I connect to the TV-PC from my laptop, so basically I see windows inside windows, then when I move my mouse around on my laptop I see it moving on my TV, this is great for playing MOVIES or MUSIC or BBC iPLAYER

And as long as you can install VNC to a LAPTOP and connect it to your WIRELESS network then any LAPTOP would be able to control your TV

In a few weeks I will be moving my PC into the backroom using a 10Meter VGA cable, trust me they work perfectly I already have 2 of them in my boys room no loss of signal or ghosting whatsoever

hope that helps

see pic below of my laptop with TV

1 more point to add, my TV only has a NATIVE RESOLUTION of 1024 X 768 and this can still play 1080 MOVIES at amazing quality, I have 700MB AVI films, 720 HD and 1080 HD and when I go from one to the other the difference is definitely noticable, my TV is also only HD READY and these films are being sent down an RGB cable and not HDMI

Works just fine for me, recommend it to anyone!!!

also worth noting that not all DUAL CORE laptops will play HD movies, my COMPAQ nc6320 plays them only just with 3GIG RAM CENTRINO DUO CPU, and iv'e seen brand new laptop's with 17" screens that can't even play 720

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