[bnewton]

I've been trying out my Leeza with an SDI equipped RP-56 and noticed there is a lot of video "noise" in the picture when I use SDI. It's absent when using component.


The noise manifests as sort of random pixels speckling the screen with random colors. When I first hooked it up, the noise was terrible, but it seemed to get better. After an hour it was only noticeable in dark scenes, but was definitely still there.


I had the component video cables also hooked up, so I could switch inputs back and forth easily. I didn't disconnect them to see if that would help, but it really shouldn't anyway.


Any ideas?

 

[markrubin]

try a different cable


I noticed this too and it was the SDI cable- to my surprise, a cheaper BNC jumper cable worked better - so I suggest you try different cables


Mark

 

[Orio]

I have not seen this problem. Hence, as suggested, it might be a bad coax cable or defective component. Suggest you try changing the cable and if that does not work contact KeyDigital.

 

[Tom Strade]

Quote:

Originally posted by bnewton I've been trying out my Leeza with an SDI equipped RP-56 and noticed there is a lot of video "noise" in the picture when I use SDI. It's absent when using component. The noise manifests as sort of random pixels speckling the screen with random colors. When I first hooked it up, the noise was terrible, but it seemed to get better. After an hour it was only noticeable in dark scenes, but was definitely still there. I had the component video cables also hooked up, so I could switch inputs back and forth easily. I didn't disconnect them to see if that would help, but it really shouldn't anyway. Any ideas?

Was this one of our players? I can't find you in our database. But if it is one we modified, no matter how you came across it, I can help you out. Contact me via PM and we'd be happy to take a look if the new cable doesn't work for you.

 

[Glimmie]

This is one area where these expensive esoteric cables may actually be worse than a cheap one. SDI needs a bandpass of 100khz to 500mhz. This means a true 75ohm coaxial cable. A cheap piece of RG6 with F to BNC adaptors will work fine. Some of these fancy cables have twisted pair construction or some other non-75 ohm construction. SDI isn't impressed by the "open sound stage, lucious midrange" claims.


You can probabaly tell by now I don't like snooty expensive cables!

 

[oferlaor]

I had this noise too on SDI. The affect was nearly identical to what you described. After a while, the noise died down. I can't see it anymore (I'm not using the LEEZA, but another SDI scaler!).


I couldn't track it down, but now it's gone!

 

[bnewton]

The cable I'm using is one I made up from Liberty Cable serial digital RG-6 with Liberty Cable Pro BNC connectors. So the components are good, but my construction may be suspect.


I'll give another cable a try and if that's the problem, I'll redo my cable. Thanks for the pointers, I'll let you know what happens.

 

[oferlaor]

I think I switched cables (from a thick BNC cable to a thin standard one).


But the noise wasn't effected. Try keeping it running for a while and see if it dissapears.

 

[asinshesq]

Quote:

Originally posted by oferlaor I had this noise too on SDI. The affect was nearly identical to what you described. After a while, the noise died down. I can't see it anymore (I'm not using the LEEZA, but another SDI scaler!). I couldn't track it down, but now it's gone!

Me too. Mike Tsinberg (head genious at Key Digital) was over at my place to look at my setup and he mentioned that the Leeza has to 'balance' the sdi cable and that takes a while, so Ofer may be right. You should email Mike and find out if you need to do anything to facilitate the balancing.

 

[Mike Tsinberg]

Barry,


We found a cable that works very well.


Sen us an emali and we wil direct you.


Thanks,


Mike

Quote:

Originally posted by bnewton I've been trying out my Leeza with an SDI equipped RP-56 and noticed there is a lot of video "noise" in the picture when I use SDI. It's absent when using component. The noise manifests as sort of random pixels speckling the screen with random colors. When I first hooked it up, the noise was terrible, but it seemed to get better. After an hour it was only noticeable in dark scenes, but was definitely still there. I had the component video cables also hooked up, so I could switch inputs back and forth easily. I didn't disconnect them to see if that would help, but it really shouldn't anyway. Any ideas?

 

[Glimmie]

Quote:

Originally posted by asinshesq Me too. Mike Tsinberg (head genious at Key Digital) was over at my place to look at my setup and he mentioned that the Leeza has to 'balance' the sdi cable and that takes a while, so Ofer may be right. You should email Mike and find out if you need to do anything to facilitate the balancing.

This is either a mis-understanding or hogwash! If Mike is refering to auto equalization in the SDI reciver, that takes a few microseconds at worst. If we are going to use professional interfaces then let's not use the "cable burn in" crap. If the cable, SDI transmitter, and SDI receiver are properly designed, it should work from 0 to 1000feet without any problems.

 

[zxe018]

I, too, have experienced this when I first hooked up an RP91 with my Leeza using a Bettercables BNC-to-BNC cable. I switched the Bettercables to an Audioquest cable, and everything has been working flawlessly.


Hopefully changing cables will work out for you.

 

[oferlaor]

Looks like alot of us experience this when the unit either warms up for the first time, or something.


At first, I thought something must be wrong with my setup, but when it went away after a few minutes - I guessed it was something I did wrong...


It would be interesting to switch cables and see if that causes the noise to reoccur.

 

[occammd]

Glimmie,


Is SDI rated at 1000ft?


Unless they have active termination components then cable burn in(whatever that is) is a farce. This is a digital interface, I can understand zero tracking for some analog inputs, but haven't seen it on digital. I thought this was a differential digital interface with clock restoration?

One thing you might try is to ensure your grounds on your equipment are common. You may be getting a high common mode and saturating the drivers. I'll look up the part to see if this is possible.


Could also be an impedance mismatch due to the cable. Tom, What is the termination network for both side of this cable and what do they expect the characteristic impedance of the cable to be?


Thanks,

Ray

 

[occammd]

Sorry, saturating the receivers, not drivers.

 

[oferlaor]

occammd,


Don't think so. I think 150-200ft is about it without a driver (or something).


Don't know what the reason is for this video noise, but I guess we've all seen it, so it's not a figment of our imaginations... It certainly goes away afterwards.

 

[occammd]

I now see what they mean by balancing the cable. If they have incorporated this part into their receiver then it has the ability to minimize reflections and compensate for cable length. I am assuming by one of the above responses that they have.


However, whoever designs the receiver end needs to specify for you what type of cable (twisted pair or coax) and the optimum length.

The reason for this, as you will see in the datasheet, is that there are 2 resistors that are selected in the design based upon cable type and a timing capacitor for the feedback portion of the receiver based upon cable length.


In any event, this loop compensation should appear fairly instantaneous to the user, you should not have to wait for it. Nice part.


part:
http://www.national.com/ds/CL/CLC014.pdf

 

[occammd]

ofer,


You can also see a chart in the above pdf that shows the maximum cable length versus data rate. I am not sure of the data rate. Tom would know.

 

[obie_fl]

Just to add a data point I had very good luck with an 18" PVC2 Precision Video Transmission Cable from avcable.com. I tried various other cables and they all had the noise problem to some extent.


Tom

 

[JeffY]

Its probably a grounding issue of some kind.