CurtPalme.com Home Theater Forum

Gino · Posted: Tue Dec 09, 2008 12:50 am Post subject:

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

Well what can I say, MP should know the limitation of the Barcos video path as well as I do so I'm not sure now he could claim that for the cine9 or any Barco. And yes him and I have had this discussion before.
Even the Marquee boards which use a similiar chip as found in the Cine/S series will have the same limitations, and that is one of BW.

Gino · Posted: Tue Dec 09, 2008 2:32 am Post subject:

He actually claimed that his 8500 outperformed the Cine9 when it came to 1080p72

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

I'm not about to challenge what he saw on PJs that he worked on.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

VDC does have thier 8500HR that does do 1080p easily and I think its @72, TSE mentioned it somewhere else but not in this post i am linking:

http://archive2.avsforum.com/avs-vb/showthread.php?t=708814&highlight=8+inch+tube+does+1080p
He has a new VNB that they were working on that really improved on BW, if we ever see these out on the used market
will be another thing, they are like 1700 each new IIRC. They also did work on the VIM. I do believe this is what really pushed mike to get 10870p@72 from his 8500. he Visited TSE and saw that and coudln't let it go and had to try. I think its awesome he pushed himself to achieve that. But if I could only get my hands on those VNB's and Vim ! Very Happy

And this
pic from TSE is much sharper than the one MP has posted. But remeber this is set up on a small screen and
with the PJ perfectly centered on the screen. So i do think Mike has got 1080p on the 8 inch tubes no problem but not as good as this!!

TSE does 1080p on an 8 inch tube

Athanasios

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Athanasios, what is the bandwith of the 8500HR? What tubes are in it (are they just 180s like the 8500 MP was playing with or P16s or better)? How did MP get the bandwidth up over 180 as Greg is the only one I know trying that path (and on Barcos). I've not seen any Quee mod that increased the bandwidth to near that.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

I am not sure of the HR BW i know the newer VDC's are 150 , so for mike to get it up a bit more i can believe , you have to remeber on producton machines , even small quantity numbers the bean counters still use less expensive and less than optimal speced parts, there are better performing parts that would allow the high bandwidth parts to achieve there originaly tested specs that were performed in lab conditions. if you look at specs for IC's and the associated exernal parts used in testing then look at the actual use of that IC in production equipment you never find the exact recomended parts, they always go the cheaper route.

Ok I found a one on one off shot from mikes pics 1080p@72 not as sharp as TSE's but close. and its all three colors at once so its not as sharp as if it could be on a single color. And I think he was useing 180 tubes as he says they can relove 1090p@72 fully. I know he had more pics of the 1:1 but its a pain to look for all his posts.

Mike Parkers 8500 ar 1080p@72

Mike parker 909 1080p@72

they look pretty close.

TSE does 1080p on an 8 inch tube

Athanasios

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Thanks. Anthanasios. One caveat, I'm not saying it can't look decent with typical HT content, it just will not be razor sharp, nor as sharp as lower bandwidth.

That said, let's consider tse's top left corner (which you said tse's looked better than MPs). Note the MTF of the black and white horizontal lines in the 2 on-2 off pattern--that is what they should look like. Compare that to the 2-on 2-off vertical bars--not even close.

But, the real tell-tale sign is the thick white box around the test patters. Look at the outer left edge of that--way soft. Imagine that is a planet surrounded by space--it is going to look more like a cotton ball than a planet! This part of the picture proves it is only "adequate" at 1080p/72, not what it should be.

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

I'd have to agree with Dave on this too, looks pretty soft to me. What test discs have these patterns on them so I can run a test on mine?

mp20748 · Posted: Wed Dec 10, 2008 12:29 am Post subject:

The patterns shown of mine are at 72HZ. TSE's are at 60HZ.

The bottleneck issue is not true on the Marquee boards that uses the AD835 chips as gain (contrast). Those chips are rated at 250Mhz. The board that I was using in my test for the patterns were modified 03 VIM's that had the AD834's, which are rated at 500Mhz. I'm also using lower resolution tubes compared to the newer higher resolution 8" tubes VDC now uses.

Also, what I'm claiming has also been verified at VDC on my visit and as TSE points out, the only way to make a bandwidth claim is to support it with the 1:1 pixel pattern.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

mp20748 · Posted: Wed Dec 10, 2008 1:11 am Post subject:

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

Yes that is true the 835 is rated at 250Mhz BW, but that is the -3db point, the -.1db flatness which is more telling is only 15MHz. As for the 834, yes it is rated at 500MHz -3db BW but the manufacturers datasheet is a very thin on specs and doesn't even give the -.1db spec or any graphs of BW vs rolloff etc. Even trying to compare the 834 to the 835 is hard to do because they don't even list the same parameters with the same tests circumstances. This isn't unusual for IC manufacturers to do even within the same family and typically if they don't give certain specs or lots of specs it usually means they're probably hiding it's poor performance.

mp20748 · Posted: Wed Dec 10, 2008 1:22 am Post subject:

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

Yes Mike as we've discussed this before I'm familiar with BW boosting on those chips but you can only take it so far before you run into other problems. Barco did no BW boosting on any of their versions, how they can make that spec claim is beyond me. That IC is still one of the BW bottlenecks in both the Barco and EH PJs.

But regardless of BW claims etc etc, if it looks good and does the job then that is what counts in the end.

mp20748 · Posted: Wed Dec 10, 2008 1:42 am Post subject:

OH.. that AD825 is a very noisy (hash) chip. it requires a ton of work to tame most of the noise. It also requires a bit of work to +/- rails to it. proper de-coupling of this chip is very important. Otherwise, it just won't do so well at those higher frequencies.

I learned a few tricks while at VDC during my visit. It's not so much what they are saying in the specs with a device as it is how and where they are using it in the chain. Impedance a few other things are very important to getting the best from the device. That's a little over my head, but I've learned a lot from Scott on this.

Also, on my G90 mods. There's also a AD835 in the video chain. That one I remove.

And as you can see from my G90 screenshot of the same resolution, I'm also pulling off 1080P / 72Hz... I'm doing something very similar to the weaker link in that chain that I'm doing to the AD835 in the Marquee's.

First screenshot taking from the lens of a modifed G90 doing 1080P /72hz

My initial