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logic28
08-19-2007, 04:49 PM
Hi, I posted this thread in VT Hardware and hardly had any response so I thought I would try this one.

As this is the most important issue ever about the VT LIVE system I am going to try to be very descriptive so forgive me for the long thread.

I have read threads regarding this before but with inconsistent statements.

As you can see from the attached photos I have built a 9U rack system which is designed to be integrated with a much larger Audio / Midi / DMX lighting rig.

Because of that the system had to be the exact size to accommodate all the necessary.

Due to a serious mistake made by Newtek rectified after my notification last year about the size of the SX-84 (the brochure and the web stated 5 U instead of 6 U), when the VT4 components arrived we knew we couldnít fit it in as it was.

So a special double-shielded aluminium housing was designed for the SX-84 in order to just squeeze it into place at the back of the rack where, by means of hinges, it would allow inspection to the 10 removable hard drive cradles.

Also, in order to keep the whole job tidy, some custom cables were constructed with better material than the standard ones to connect the BoB to the card.

These cables were also fully shielded as opposed to the standard VGA type adopted by Newtek where only some are coax. (some like the Sync are not shielded)

Now letís get to the real issue.

Diagonal lines of obvious RF noise are introduced to analog inputs going through the BoB.

Composite seems to give the best result, YC the worse and Component varies from time to time.

Needless to say this would be totally unacceptable for a live broadcast.

My immediate reaction was to test without the BoB and to the best of my knowledge the problem didnít arise.

So I have changed the cables back to the original Newtek ones.

Marginal improvement due to the external shielding, partially missing on mine for thickness reasons, but the BoB is still introducing a lot of noise.

So I am debating whether this is due to the closeness of the BoB to the motherboard + hardware or to the material of the SX-84 new housing or both!

A minimum distance between BoB and PC was never stated by Newtek or else I would have conceived a totally different arrangement.

It would greatly help to know if anyone else has experienced similar problems with unmodified equipment before I completely throw away all the complicated but most space-efficient design.

Also the typical clicking noise when the BoB audio input master is open is coming through like Iíve heard other VT users complain about before.

I guess that could just be a factory fault with perhaps a leaking capacitor discharging at a constant rate but also could be due to the new casing somewhat closer to the board at the very edges to gain space and compensate for the Newtek misprinted information.

I guess this is it but it is a lot to resolve on a system that is otherwise impeccable and very, very exciting to use.

I would greatly appreciate any input on this one.

Thank you all for your continuous support.

MAZ

http://www.logic28.com/OTHERS/VT 4/CASE 1.jpg
- VT Under Construction
http://www.logic28.com/OTHERS/VT 4/CASE 2.jpg
- Sample Shape for the New SX-84 Housing
http://www.logic28.com/OTHERS/VT 4/SX 1.jpg
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http://www.logic28.com/OTHERS/VT 4/SX 2.jpg
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http://www.logic28.com/OTHERS/VT 4/SX 3.jpg
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http://www.logic28.com/OTHERS/VT 4/SX 4.jpg
-Double Shield for BoB and Cables
http://www.logic28.com/OTHERS/VT 4/SX 5.jpg

PSegarra
08-20-2007, 09:14 AM
I had that very thing happen to me and the problem was the monitors I was using as soon as I changed monitors the noise went.

logic28
08-22-2007, 05:21 AM
I had that very thing happen to me and the problem was the monitors I was using as soon as I changed monitors the noise went.

Thanks for your reply but I need to understand:
What type of monitors did you use before and after?

Besides, I don't get it. If it was due to the monitors, wouldn't the noise still be there when plugging the video directly into the vt4 Card?

Maz

PSegarra
08-22-2007, 07:10 AM
2 Flat panel 18" Microteks plugged into my Nvidia 5700 video card and when I changed it to 2 24" 16x9 dell monitors the noise was gone.

tfrank
08-22-2007, 08:05 AM
In looking at the pictures, it seems that you have removed the SX84 from it's case. Have you inadvertantly lifted a ground or caused damage to the backside of the electronics of the SX84?

logic28
08-22-2007, 11:36 AM
In looking at the pictures, it seems that you have removed the SX84 from it's case. Have you inadvertantly lifted a ground or caused damage to the backside of the electronics of the SX84?

As I explained because of Newtek's mistake in sizing the SX-84 I it ended up 1 U too tall to fit above the back of the computer in the 9 U rack.

In order to make the BoB fit I had to design a custom case much thinner at the bottom to allow the top part of the back of the PC to fit behind it.

It is fair to say that the depth of the original case only needed to be that high because of a daughterboard that only occupies 1/4 of the total space at the very top so the distance between such board and the skin of the new case is no different from the original one.

Having said so, what we don't know is if by lowering the rest of the case some 1 cm from the main board could have made any difference to the shielding.

Personally, I think the only degradation in shielding could be due to the thickness of the material used by ourself, but having said so, we added a second shield of the same 1.2 mm alloy which also protects all VT4 to BoB cabling from any interference coming from inside the rack (PC or hard drives.)

Altogether it doesn't look any worse but possibly even better and lighter than the original less expensive steel case.

I guess we'll never know until we can borrow or purchase another SX-84 and test it away from the rack to see if there is any improvement.

Nevertheless, if there was any improvement, (as I wouldn't want it in any other location), that would only prove the vulnerability of the SX-84/cables to any RF interference of the PC thus leading us in search of alternative ways for shielding it (eg. lead sheets etc.)

Maz

logic28
08-22-2007, 11:44 AM
2 Flat panel 18" Microteks plugged into my Nvidia 5700 video card and when I changed it to 2 24" 16x9 dell monitors the noise was gone.

I see. Hmm ... but did you try with the old monitors without the BoB?

When I did it the noise totally disappeared!

So unless the monitors / VGA-DVI cables are affecting the BoB but not the VT4 card, I have little hope that they are going to have any effect on my problem.

Having said so, I remember having had your identical experience 10 years ago with my former switcher but, I must say, in that case the monitor was a CRT and not a flat screen.

Maz

PIZAZZ
08-22-2007, 06:53 PM
Sure would of been less work to just use a different rack case. a 10U instead of the 9U.

We frequently mount SX84's right on top of our PC with no noise issues. I believe your mod may have brought on some noise or possibly you just have a defective SX84.


http://www.pizazzme.com/shop/prodimages/stored/Image/prod_pics/thumb_VTtoGo.jpg

logic28
08-24-2007, 04:24 PM
Sure would of been less work to just use a different rack case. a 10U instead of the 9U.

Yes I guess a 10 U rack would have been easier. Shame the rack case we are using (EMS from London) comes in modules of 3 U at a time.

So 3, 6, 9, etc. but no 10!

The reason for using this rack is that it is simply the best rack system I've ever seen. Beside, with an interesting addition we designed 12 years ago, each block can be mounted on top of another with no external connections at all.

All connections are made internally via a cam lifted horizontal arm carrying very expensive gold-plated / ceramic interlocking connectors.

This allows us to join our VT4 to: PC for digital audio mixer, DMX lighting controllers, 2 Midi PCs, 2 Sennheiser radio mics + 1 Sennheiser monitor system, some Midi sound modules, 2 x vocalist harmony producers, all fitted on top of the bottom base containing 1 x 1000 W + 1 x 2,300 W Final Stages for PA.

All this integration allows a full show to take place with minimum human activity and of course with the aid of Young Monkey's MidiVT, the whole show can be broadcast with precise pre-determined camera switching again all automatically Midi controlled.

With the addition of a small Midi interface originally designed by myself as a camera switcher + zoom, focus, pan & tilt control, all cameras can also be governed with no human intervention.

I guess this explains why we had designed the VT4 housing around this rack case system based on the advertised size of the SX- 84 being 5 U.

During construction of the BoB new housing, maximum care was taken to avoid any kind of interference or indeed dust and moisture to enter the SX-84.
After 20 years of building blue-printed racing engines I have developed an extremely meticulous working environment similar to that of a surgeon.

But of course mistakes can occur so I will look into that.

My feeling is that, since the BoB was producing audio clicking noises prior to the mods, you might be right in saying that it is probably suffering from some kind of defect. :agree:

Adam_LightPlay
09-01-2007, 09:35 PM
Sounds like quite an interesting application. Is there a website or place we can get more info on how you are using this mega-machine?

logic28
09-02-2007, 05:56 PM
Sounds like quite an interesting application. Is there a website or place we can get more info on how you are using this mega-machine?


Not yet really! But soon I will make all this information available on my new
ď TempoTechnology Ē website.
After all it is only a question of utilizing off the shelf equipment plus a couple of trickeries to our advantage!

Maz