VideoHelp Forum
+ Reply to Thread
Results 1 to 5 of 5
Thread
  1. Member
    Join Date: Apr 2014
    Location: Falmouth, Cornwall, UK
    Search Comp PM
    Im new to working with video signals, but I've been told by a technical assistant at my university that this setup should work, but it simply isn't and wondered if anyone on here might be able to help...

    For a Final performance, Im trying to send multiple video signals from my Mac Laptop to 3 old CRT TV Monitors (2 x Sony Trinitrons and 1 x JVC)
    I've got 2 cables coming out of my Mac. They are USB and thunderbolt. They both go into a matrox TripleHead2Go DP Edition (3 way monitor splitter for seperate signals - not a standard splitter) which comes with it's own software (says no monitors are connected).


    Can be found here: http://shopmatrox.com/europe/products/datasheet.asp?ID=356

    This Matrox Box comes with 3 VGA adaptors, which I've then plugged in a VGA - 3 way RCA S composite adaptor into each - one of these badboys:


    I've then got a male to male RCA S composite extension cable (just the yellow one plugged in) from each of the 3 adaptors, into the back of the CRT TV Monitors, into the Line A Video IN port.

    Hopefully I've explained that as best i can.
    I can't even seem to find much help on the internet for sending a standard video signal from a mac to a CRT TV monitor.
    Any advice or help would be greatly appreciated.
    Thanks.
    Quote Quote  
  2. Member Cornucopia's Avatar
    Join Date: Oct 2001
    Location: Deep in the Heart of Texas
    Search Comp PM
    You need to think about video sync protocols as well as physical connectors. "VGA" is a standard physical connector, but it is also a family of acceptable formats of sizes (Horiz & Vert) and framerates/refresh-rates and sync signals.

    Your adapter is converting the physical format, but doing nothing about the size/rate/sync format. This means your monitors have a size/rate/sync mismatch with your card (or more accurately, with the individual portal output from the Matrox adapter).

    Your "monitors" - and let's be clear and call them standard TVs, right? - probably only accept NTSC-type signalling, which is often NOT in that list of standard VGA formats.

    I was going to have you try connecting direct Mac->VGA->VGA-to-CompositeRCA->Monitor for each individual monitor to see if you could match the sync better, but since you are only going video out via Thunderbolt, that won't work.

    Do a search on NTSC rates, etc. Or just get the manual for one of those monitors and see what it says about acceptable resolutions, refresh rates/framerates, and sync signal method. Then look at the Matrox's and your Mac's manual on acceptable output formats in those same categories.

    I bet you won't find any simple 1:1 matches. If so, your next option is to scrap your monitors and get some standard VGA computer monitors.

    Scott
    "When will the rhetorical questions end?!" - George Carlin
    Quote Quote  
  3. Member
    Join Date: Aug 2006
    Location: United States
    Search Comp PM
    Originally Posted by willfro View Post
    Im new to working with video signals, but I've been told by a technical assistant at my university that this setup should work, but it simply isn't and wondered if anyone on here might be able to help...

    For a Final performance, Im trying to send multiple video signals from my Mac Laptop to 3 old CRT TV Monitors (2 x Sony Trinitrons and 1 x JVC)
    I've got 2 cables coming out of my Mac. They are USB and thunderbolt. They both go into a matrox TripleHead2Go DP Edition (3 way monitor splitter for seperate signals - not a standard splitter) which comes with it's own software (says no monitors are connected).


    Can be found here: http://shopmatrox.com/europe/products/datasheet.asp?ID=356

    This Matrox Box comes with 3 VGA adaptors, which I've then plugged in a VGA - 3 way RCA S composite adaptor into each - one of these badboys:




    I've then got a male to male RCA S composite extension cable (just the yellow one plugged in) from each of the 3 adaptors, into the back of the CRT TV Monitors, into the Line A Video IN port.

    Hopefully I've explained that as best i can.
    I can't even seem to find much help on the internet for sending a standard video signal from a mac to a CRT TV monitor.
    Any advice or help would be greatly appreciated.
    Thanks.
    As Cornucopia already told you, you ideally need three standard computer monitors with VGA connections to use with the Matrox TripleHead2Go.

    Otherwise, if one of the VGA output resolutions from the Matrox TripleHead2Go matches the one of the allowed input resolutions for one of the devices below (or something similar), they could work for converting from VGA to composite video when connected between the TV and the Matrox TripleHead2Go and each TV/Moniotor:
    http://www.startech.com/AV/Converters/Video/High-Resolution-VGA-to-Composite-or-S-Vide...verter~VGA2VID
    http://www.cablestogo.com/product/29548
    You may or may not get a perfect picture.

    The composite+S-Video+stereo audio adapters like the ones you bought are useless for what you are trying to do. Simple cables like that don't turn a VGA signal into a composite video or S-video signal that a TV or TV/monitor can use. They only work for a few video cards that can output an S-Video or composite video signal through a VGA-type port, or for transmitting an A/V signal through an existing VGA cable run to a projector in in a classroom/auditorium. Neither of these scenarios apply to what you are doing.
    Last edited by usually_quiet; 29th Apr 2014 at 16:04.
    Quote Quote  
  4. Member Cornucopia's Avatar
    Join Date: Oct 2001
    Location: Deep in the Heart of Texas
    Search Comp PM
    Exactly.

    Scott
    "When will the rhetorical questions end?!" - George Carlin
    Quote Quote  
  5. If you must use composite (or s-video) displays you'll need three VGA to composite scan converters.

    http://www.amazon.com/Lenkeng-104724-Monoprice-VGA-RCA/dp/B001CJOLBW/

    Picture quality won't be great, worse than DVD, even if you buy expensive ones.

    http://forum.videohelp.com/threads/283861-VGA-to-S-video?p=1756748&viewfull=1#post1756748

    Cheap ones like that suffer from tearing too.

    http://forum.videohelp.com/threads/361433-HTPC-Image-Quality-Problems?p=2293418&viewfu...=1#post2293418
    Last edited by jagabo; 29th Apr 2014 at 19:15.
    Quote Quote