Visual Cortex Black Level Calibration and Pre-2016 Identification

I am mixing between the composite outputs of two Visual Cortex-based systems with a V4EX. Each VC is generating its own sync and is in the same configuration, as follows:

Mix A ON,
RGB Color Controls 100% CW
VC Composite > V4EX > PVW

Is there an adjustment I can make on VC2 so that its white output is the same as VC1 in Line #3?

sheet_mi_vc_white

I discovered a similar difference between the white output of two Marble Indexes. I am mixing keyed footage for a project and the difference is too noticeable to work around, hoping there is something I can do at home to work it out!

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Might be a dumb question, but have you tried switching which input of the the V4EX they’re going into, to make sure the problem isn’t on that end?

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Here is the output of each VC on each channel of the V4EX. (I am also generating bars from an AJA Ki Pro.) I notice a similar difference when capturing component out from each VC directly.

sheet_vc_aja

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We frequently calibrate black levels when servicing Visual Cortexes at LZX. Contact support@lzxindustries.net if you would like to send yours in.

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Is this black level related? If so, what tools would I need to make the adjustment at home? If it isn’t reasonable to do something like this at home, would I need to send in both Visual Cortexes to get them to match?

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Here is the black level calibration procedure. Since black is 0V and white is 1V, adjusting your black level should also adjust your white level.

Tools needed:

  • Visual Cortex with Power

  • Small flathead screwdriver

  • Multimeter

Procedure:

  1. Power up the Visual Cortex.

  2. Set multimeter to read DC voltage.

  3. Locate the “0v” pad on the rear of the unit, near the 16 pin power header. Place the negative probe of the multimeter on this 0v pad.

  4. Locate “Black Level Adj.” trimmer pot on the rear of the unit. Note the three pads to the left of the trimmer pot. Of the three pads, place the positive probe of the multimeter on the CENTER pad.

  5. While holding the multimeter probes on the pads, adjust the Black Level Adjustment trimmer until the multimeter reads 0.000 volts. This completes the Black calibration procedure.

Visual Cortex Black Calibration 1

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I followed the steps in the black level calibration procedure. The initial reading on the multimeter was 0.005 volts, and adjusting the trimmer to the right a dozen full rotations or so brought it to 0.003. The level doesn’t seem to be decreasing anymore.

If it has to be sent in for calibration/repair, would you need both units to match them?

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Don’t give up! Keep turning. It takes several turns to move .001 and it’s an infinite turn trimmer.

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I’ve turned the trimmer to the right about a hundred total times, at one point the meter was reading 0.001. I kept turning to the right hoping to get it to 0.000, but now I see a bright leading edge on the left side of the screen along with some tearing or noise. The multimeter now reads 0.004.

I think VC2 may be a pre-2016 unit?


For comparison, here is VC1:


If you can get back to .001, you should be fine. Anything under .002 will be read as black.
Also, this is what we do when we calibrate a Cortex: Set all front panel switches to their default positions (middle setting for 3-position switches and down for 2-position switches). Set slider fully left and all knobs to center positions. No signal present at inputs.

Getting two modules to exactly match may be possible, but minor variations are not unusual.

Could you compare the front panels in the attached pictures? I think it’s possible the first posted, with the green shifted pcb, is a pre-2016 unit. The printing looks different and the channels for the switches are shorter than the second unit pictured.

If this is the case, would the repair/update mentioned in this thread affect the output?

As a final note, could you check the OP and let me know if the difference in white is within tolerance for ‘minor variations?’ Apologies for the repeated inquiry, just trying to understand what is possible with the equipment I have got!

That first Cortex is an early one. Send a message to support@lzxindustries.net, if you would like to set an RMA for the rework/firmware update. The white level is within tolerance, but it also might be possible to improve it.

To keep the discussion of Visual Cortex in a single thread, here is an answer to the question from this similar thread.

As mentioned in the earlier post you linked, early Visual Cortex modules (produced before December 2016) lack the rework and firmware of modules produced after that date. The differences you’ve identified in the panel are one way to tell the early modules apart. But there are few of those modules in the wild that haven’t been reworked and most users won’t have noticed that theirs does not have the rework.

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Newer Visual Cortex (new 0805 caps)

Older Visual Cortex (no rework performed yet)
image

If you see older Cortex with rework performed (new caps stacked on top of existing ones, etc) then your circuit should be performing the same as the newer ones.

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Does the V4EX have ProcAmp controls? It might be a whole lot easier to just ‘match these in post.’

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Not per channel unfortunately, would be interested if you know about cool mixers that do though!

The venerable AG-MX70 :wink: There are also broadcastBut I don’t know your other requirements, it’s probably a topic for a separate thread…

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