CurtPalme.com Home Theater Forum

Melifluonze · Posted: Fri Oct 10, 2014 11:00 pm Post subject:

So, I'm not an expert in these things, but RGBHV is analog at over 100MHz... You have a transmission line. The impedance matching of your cable to the VGA card and to the projector is critical. If it isn't properly matched, you will perceive the ringing in the cable as a loss of resolution. If you look at a strong transition, you may actually see the ringing as a ghost or fuzzyness next to the transition on a test pattern.

Video cables and interfacing is extremely critical to get good results at 1080p with analog.

DVI-D and HDMI are purely digital, so there is no loss across the cable (and there is no point in spending any extra money on them!. That's why the Moome card is so good... BUT! The Moome card still has to convert to analog to drive the VIM of the projector... So if the Moome card outputs are not properly matched, you can still get ringing!

Melifluonze · Posted: Fri Oct 10, 2014 11:00 pm Post subject:

So, I'm not an expert in these things, but RGBHV is analog at over 100MHz... You have a transmission line. The impedance matching of your cable to the VGA card and to the projector is critical. If it isn't properly matched, you will perceive the ringing in the cable as a loss of resolution. If you look at a strong transition, you may actually see the ringing as a ghost or fuzzyness next to the transition on a test pattern.

Video cables and interfacing is extremely critical to get good results at 1080p with analog.

DVI-D and HDMI are purely digital, so there is no loss across the cable (and there is no point in spending any extra money on them!. That's why the Moome card is so good... BUT! The Moome card still has to convert to analog to drive the VIM of the projector... So if the Moome card outputs are not properly matched, you can still get ringing!

Melifluonze · Posted: Fri Oct 10, 2014 11:00 pm Post subject:

So, I'm not an expert in these things, but RGBHV is analog at over 100MHz... You have a transmission line. The impedance matching of your cable to the VGA card and to the projector is critical. If it isn't properly matched, you will perceive the ringing in the cable as a loss of resolution. If you look at a strong transition, you may actually see the ringing as a ghost or fuzzyness next to the transition on a test pattern.

Video cables and interfacing is extremely critical to get good results at 1080p with analog.

DVI-D and HDMI are purely digital, so there is no loss across the cable (and there is no point in spending any extra money on them!. That's why the Moome card is so good... BUT! The Moome card still has to convert to analog to drive the VIM of the projector... So if the Moome card outputs are not properly matched, you can still get ringing!

Melifluonze · Posted: Fri Oct 10, 2014 11:03 pm Post subject:

Freaking triple post... blah... sorry folks.

**AnalogRocks** · Posted: Fri Oct 10, 2014 11:20 pm Post subject:

What'd you say? Laughing

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

I took the most possible care to match to the vga card. I used a print with a vga connector and connected coax to it. Than I had 6 m high quality coax with very low atennuation and bnc plugs on the other end off cause. However that was worse than using a 30 cm complete vga break out cable. The short cable can not it any way distort the signal it was all to short and with perfect connectors. But still I got not the 1:1 resolution Casey has. My video card is an Asus 750ti but I also tried other nvidea and ati cards and even a mac adapter all with the same result. The mac vga adapter being the best 1:1 but also noisy.

So if it is not the gigabyte implementation than I don't know what it could be. I have a gigabyte card comming in next week. Nice for my collection Smile

the whole thing is purely out of curiosity how some can have very good results with vga cards and other don't. There must be something they are doing right.

The extron was what I was looking for and is next on my wishlist. Thanks!

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

And to add even my marquee with modified video chain does not get nowhere near Casey picture using the 30 cm breakout and the asus 750 ti. Caseys barco is not modified and the video chain is not able to get near a marquee so all experts say. So I conclude my video card must be much worse than Caseys. So Asus must be very bad and Gigabyte very good or perhaps they just made one model good.

@Casey is it not possible for you to test anothe brand video card? Did you get the same 1:1 with the 9800? Or could you try another cable? It would be of great help to us.

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

Torub it in Caseys picture is even better than Francicus 1:1 who has a complete modified video chain by Eisemann and uses the best Moome special develloped for him. Even Eissemann is unable to produce the Casey picture after 10 years working with Barco. And he must have signal generators. If any of this is not true please say so.

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Cables are in the wall now, and i dont have anything else long enough to reach.

I didnt test 1:1 with the 9800GT, it is a Zotac, and image quailty on that is not as good.

I dont reckon my 1:1 was better than Francisco, probably just a better angle and better sharper picture. His picture seemed to be a bit softer, which wont be his on screen image, thatll be the picture he took, and i think his was 72Hz, mine was 60Hz

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

How did you attach the coax to the PCB you made?

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Chances of testing other cards are possible, but not in that same computer, and im not sure what other brands i have.

I think i have two Genuine nVIDIA 8800GTS cards, as in they are not any other brand name, just straight up reference board nVIDIAs. I dont know how its done these days, but way back there were some brands using reference boards and some that did not, however their changes may have been very minor, close scrutiny showed varying results among brands, and it generally followed their price point. One brand may have released 3-4 different cards under a very simular name, but at different prices, and while they appear to be extremely simular in terms of performance, its the finer details that were different.

Its not only the video card you need to look at here either, everything right down to the case can have an effect, especially things like WiFi cards and cheap power supplies. If theyre causing some sort of harmonic through there anywhere then this could be an issue.

Cheap fans can also be a real pain in the arse, they are a DC load, but the motor is still driven in an AC form, being an electronically commutated permenant magnet motor, if not suitably filtered can spit out all sorts of noise which will change with their speed.

The machine im using here is ( or was ) worth over 3 grand, its got very high quality parts right through, and that could be making a difference.

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Not the angle as such, but the quality of the photo i took, as in maybe he was a little less steady of hand when he took it. I havent looked at his picture on a computer, only on my phone, and to me it does look better than mine in terms of colour level in the H and V.

Im not sure why you think or expect 6m length of cable is going to add to bandwidth. I dont think the cable length has much at all to do with it.

Other PC parts WILL have an impact, they can produce interference as well as harmonics.

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

I think Redfox you are on the wrong path again. I think the VGA card has the least impact in your video chain. as you already know I measured the outputs of some VGA cards, and while the outcome was varying somewhat, but I tested nearly all of them in my HTPC and with my projector as well. Then a NEC 9PG xtra, which seems to have better BW that the barco, and even with that I couldn't see any real difference between them. On the other hand we all like to compare our CRT projectors to others' but we often forget that these machines are 10+ years old, and each one has an own story, how it was used, how it was stored etc. None of them the same even if the badge on it says so! You couldn't even know if they were the same when they came out from the factory, yes, surely there was a quality management in the factory, but still there could be machines that performed better than others.

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

I am not saying i reckon the different brand of video card is going to make a significant difference, i cant see it making a big difference at all.

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

To compare the images more carefully. Which one looks higher bandwidth?

Casey's 1080p@60 nothing modified and with PC through vga. Cine Max.

Francisco's 1080p@60 fully modified and with Moome. 909 not a splitpack!

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

Hi on the first point. My point is when I read the wiki article they say:
One-stage low-pass RC network

http://en.wikipedia.org/wiki/Rise_time#Rise_time_of_cascaded_blocks

I think when you have a steep filter this calculation does not work or am I wrong?