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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Pro AV Forum => Topic started by: Kellen Tyburski on November 22, 2011, 04:54:25 pm

Title: VGA vs. RGBHV runs
Post by: Kellen Tyburski on November 22, 2011, 04:54:25 pm
Hey all.. Hoping you could shine some light on this for me... I've working quite a bit around NYC (a lot of hotel AV) and I notice certain crews stick to VGA, and others are loyal to RGBHV cables. Neither really seems to know exactly why. Sometimes there doesn't seem to be much of a reason, (ex: vga output on switcher --> RGBHV breakout --> RGBHV cable -- back to vga input)

 From the research I have done, RGB analog signal requires sync, and in a VGA cable H and V sync are carried on PIN's 13 and 14, and with rgb-hv cable the H and V sync are carried on separate cables, So I don't see much of a difference in terms of Sync.

Generally speaking, which cable is best to use, and why? Does VGA suffer from "multiplexing" just as composite/s-video cables do?

Thanks for any advice or resources you might be able to point me to!

-Kellen
Title: Re: VGA vs. RGBHV runs
Post by: Gianfranco Favero on November 22, 2011, 05:36:49 pm
Hey all.. Hoping you could shine some light on this for me... I've working quite a bit around NYC (a lot of hotel AV) and I notice certain crews stick to VGA, and others are loyal to RGBHV cables. Neither really seems to know exactly why. Sometimes there doesn't seem to be much of a reason, (ex: vga output on switcher --> RGBHV breakout --> RGBHV cable -- back to vga input)

 From the research I have done, RGB analog signal requires sync, and in a VGA cable H and V sync are carried on PIN's 13 and 14, and with rgb-hv cable the H and V sync are carried on separate cables, So I don't see much of a difference in terms of Sync.

Generally speaking, which cable is best to use, and why? Does VGA suffer from "multiplexing" just as composite/s-video cables do?

Thanks for any advice or resources you might be able to point me to!

-Kellen

Not sure why but with rgbhv you can do longer runs. with vga over 20m you start to get bad ghosting and stuff. The cables are more sturdy and the bnc connector is better than the vga.
Title: Re: VGA vs. RGBHV runs
Post by: Kellen Tyburski on November 22, 2011, 06:20:45 pm
Not sure why but with rgbhv you can do longer runs. with vga over 20m you start to get bad ghosting and stuff. The cables are more sturdy and the bnc connector is better than the vga.

I'm assuming (would love if someone could clarify) that is because Red/Blue/Luma are house separately from each other, as opposed to VGA?
Title: Re: VGA vs. RGBHV runs
Post by: John Livings on November 22, 2011, 06:48:16 pm
Rob Sayer has a website that might be helpful. (On Stage Lighting)

http://www.onstagelighting.co.uk/media-video/video-signals-idiots-guide-dummies/

Regards,  John
Title: Re: VGA vs. RGBHV runs
Post by: Collin Donohue on November 22, 2011, 06:58:53 pm
From the rentals perspective, the cables WILL gr damaged at some point. For us, we use RGBHV cables and use 6" adaptors when VGA is needed because its easier to repair a bad BNC connector than a VGA connector.

We still have VGA in our inventory, but only 50' and under for direct computer to projector connections.
Title: Re: VGA vs. RGBHV runs
Post by: Glenn James on November 22, 2011, 09:36:11 pm
VGA is just a type of connector fitted to the RGBHV cable. The standard is the same.
You can often go further using RGBHV cabling though as VGA cables generally use thin cables with less adequate shielding to fit within the small cable jacket.
Title: Re: VGA vs. RGBHV runs
Post by: Brian Tennyson on November 23, 2011, 05:09:08 pm
VGA is just a type of connector fitted to the RGBHV cable. The standard is the same.
You can often go further using RGBHV cabling though as VGA cables generally use thin cables with less adequate shielding to fit within the small cable jacket.

Absolutely right, Glenn. A VGA cable might have other pins active, like monitor ID pins for communication between a display and a graphics card. Power (pin 9) and I2C clock (pin 15). Usually these cables are made for short runs so they use a 22 gauge or smaller cable for the video. So really RGB is a subset of VGA. But there is nothing that would preclude you from terminating a VGA connector (correct name is D-Sub 15 or DE15) on a set of five RG-11 cables.

The smaller cables are what create ghosting.
Title: Re: VGA vs. RGBHV runs
Post by: Steve Kennedy-Williams on November 23, 2011, 05:21:36 pm
From the rentals perspective, the cables WILL gr damaged at some point. For us, we use RGBHV cables and use 6" adaptors when VGA is needed because its easier to repair a bad BNC connector than a VGA connector.

We still have VGA in our inventory, but only 50' and under for direct computer to projector connections.

As the repair manager for an AV company, I'd add.

1. Field repair of BNC is much easier than VGA.
2. We use a RGBHV + 1, so we have a spare channel on each cable. one goes down, we don't have to replace the cable.
3. Easier to use locking connector. The bayonet style lock on BNCs is much easier to deal with than thumb screws.
Title: Re: VGA vs. RGBHV runs
Post by: Kellen Tyburski on November 27, 2011, 08:03:27 pm
Awesome responses, thanks guys. Right after posting this I ran out and bought Audio/Video Cable Installer's Pocket Guide by Stephen Lampen - which is some really great stuff..

Thanks again,

K