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component video bandwidth

Discussion in 'AV Receivers & Amplifiers' started by PC Nut, Apr 11, 2004.

  1. PC Nut

    PC Nut
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    Component video bandwidth:

    I have seen various amounts of video bandwidth on different AV amps/receivers ranging from 30mhz upto 100mhz. Although you would probably make a decision between two amps with identical features you would probably base your final decision on the 100mhz option due to the higher figure quoted and pay accordingly for this feature.

    My question is, why would you need a 100mhz in the first place for video bandwidth and how much bandwidth is actually needed.

    Can someone, enlighten myself and probably a few others on the above.... Many thanks:confused:
     
  2. PC Nut

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    No one brave enough to add comment!
     
  3. Gatto

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    The Higher the resolution, the greater the bandwidth required. Therefore the higher the MHz the less compromised the picture is. I think that a 50 Mhz bandwidth will be good enough, not to compromise any sources and it is quite impossible to recognise any loss or degredation in the image at that bandwidth. New receivers come installed with a 100Mhz bandwidth, but as most Receivers base there specs on gimmicks, this is another speck within the list for marketing reasons.
     
  4. PC Nut

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  5. gmt steve

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    Was going to say, the most you'll ever need (for the foreseeable future) is 60Mhz, which is what the holy grail of 1080p video needs, but the link you supplied says it all really.
     
  6. Nic Rhodes

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  7. Nic Rhodes

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    60Mhz, I wish, it would make things much easier, 300Mhz + is what I would look to for premium performance
     
  8. chris l.

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    For bandwidth / switching see:

    http://www.zektor.com/hds4/componentvideo.htm

    Basically the article states that RCA connectors (design limitation) are limited to circa 200mhz switching ability and BNC connectors are the way to go for the highest quality switching.

    I used to use a Denon 3802 for switching and I thought it was OK, then I got a Yamaha RX-V1400 and the picture quality did slightly deteriorate through my Z2 onto a 100" screen.

    Then I went for a Denon 3803 and it improved to the best I had ever seen it.

    Then I got a Zektor HDS4.2 (for switching convenience) and it is now again the picture quality is the best I have seen.

    Obviously the best is from my DVD straight into the Z2 without any switch, though I can't see any picture quality loss / improvement when the Zektor is in the loop of not.

    So:
    3802 could switch circa 50 mhz
    RXV1400 could switch 60 mhz
    3803 can switch 100 mhz
    Zektor switches circa 200 mhz

    With my eyes I could see the difference in picture quality in each step I took. Only subtle but it was there.

    Regards,

    Chris
     
  9. PC Nut

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    Chris:
    The problem is how are we to choose the right equipment if we want to pass through/upsample our signals to component level if the information for a particular AV amp is not readily available. Good reviews are hard to come by and ones that go in to this sort of depth, well I have never found one yet. My knowledge of RF and bandwidth are reasonable and the only indication as to how good an AV amp might be is almost guess work. I think the best we can hope for is by opting for the largest bandwidth available (100mhz) and that we are future proofing our purchases to some extent.

    As for cables and connectors:
    Yes they can have a profile across the bandwidth that may not be desirable, lower frequencies suffer the least but may still have unwanted suck outs at a particular frequency and the higher the frequency used the more attenuation of that signal.
    Generally short runs are not a problem.
    The most we can do to help this is good quality cables that are at least double shielded and good quality low loss connectors, at least this would not worsen the situation

    If you can find reference to how good an AV amp might be at
    signal switching/upsampling then please let me know other than this we can only go by word of mouth from a particular user, of that equipment and how they might perceive the picture to be in their opinion.

    Ps sorry for the long post.
     
  10. PC Nut

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    Frequency Response ..................... 5 Hz to 40 MHz dB(+0 -3)
    This reading is taken from the ax10 pdf document I assume the later part (+0 -3) refers to the signal levels at the frequencies given respectively and shows that their is a 3db roll of over that frequency range, this is before we even bring into the equation of cabling and connectors. I would have thought re-slopping the signal would be beneficial to the consumer if I am reading this correctly, please say otherwise if you know differently....
     
  11. chris l.

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    PC Nut,

    I agree with you. The lack of info in reviews about an AMP's video switching capabilities is very poor, especially when you consider the amount of AV kit sold and it's intended use etc.

    I also agree that if you can get 100mhz switching this will cover most applications for UK quality TV signals and interlaced DVD, obviously the more the image is stretched (the bigger the tv or screen) the more the detail in the image will be tested.

    However, when I tried the Yamaha 1400, which on spec was slightly better than the 3802, it actually degraded the image in a side by side comparison. So it may say it can do it on the tin etc, but it's the quality of the manufacturing / components / path that needs to be considered.

    I tend to find that with respect to component switching there is more info on the US (understandable) sites and especially so on the avsforum.

    My understanding is in line with yours on the roll off of -3.

    As per Zektor , ideally you need (allowing for cable loss also) the following switching ability for the differing input / output.

    NTSC= 41 MHz
    480p (wide) = 113 MHz
    720p = 255 MHz
    1080i = 255 MHz
    1080p = 511 MHz

    Regards,

    Chris
     
  12. cwick

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    There's some numbers on this page for Denon, Onkyo, HK and Sony stuff. Didn't realise how poor my Denon 2802 is in this respect .. 27Mhz :eek: barely worth the effort, surely.
     
  13. PC Nut

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    chris l:
    Thanks for the info Chris, i will check out avsforums for more info.

    cwick: I see what you mean 27mhz is a bit tight but this should be ok for component out on dvd
    Info from link above......

    How much bandwidth you need to pass a component video signal depends on what video source you are using. Any receiver with component video switching will be able to pass the 480-line interlaced output of a DVD player or an HDTV tuner without picture degradation. To pass a progressive-scan DVD signal accurately, however, a receiver needs component video bandwidth of at least 12 MHz. The most demanding video source is a progressive HDTV signal, which requires approximately 30 MHz of bandwidth for flawless transfer.
     
  14. cwick

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    I'm using a 720p source ... so it's a good job I've got a Zektor switch arriving tomorrow :D
     
  15. Jackass

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    If RCA connectors have a limitation of 200 Mhz and the above figures are correct then scalers like Lumagen's with RCA output connectors are the 'bottle neck' so to say when outputting 720P and above.

    Is this correct? :confused:

    Steve.
     
  16. sticker

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    I also find it strange if the RCA connectors are limited to this figure. My AV8 has a 300Mhz bandwitdth. Why would Arcam do that? I'm sur ethat I've seen John Dawson say that the AV8 can do 300Mhz so the article can't be correct or John Dawson can't be correct, I tend to believe more what JD has to say.

    I agree with the BNC connectors, the Beekeeper has been saying this for a long while

    Regards
    John
     
  17. chris l.

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    Don't confuse bandwith with frequency.

    As per Zektor

    "Most RCA connectors start to cause severe impedance variations around 200MHz. In our design tests, the HDS4 started to show excessive variations of the signal at these frequencies. Professional video equipment use BNC connectors for this reason, since they are designed for radio frequencies up to and above 300 MHz.

    and summarised form http://www.zektor.com/hds4/componentvideo.htm =

    1080p = 1920x1080@30 = 52.0 MHz bandwidth your equipment will attempt to send the the display at.

    The 0.5dB ... is the standard -3dB bandwidth rating you will need for everything that will touches the video signal (cables, distribution amplifiers, switchers) = 223 MHz bandwidth.

    If you will be running a long length of cable (more than 30 to 40 feet), or using multilpe distribution amps or multiple switchers, 0.1dB to specify the standard -3dB bandwidth rating you will need for everything that will touches the video signal. = 511 MHz bandwidth.

    Regards,

    Chris L.
     

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