Visual Cortex pre-encoder expander

Yeah I’d be down for a prebuilt, Sure I could figure out fitting the header.

Hey, could a little header kit be sold w the modules? That would make things so easy!

the full kit im planning will have pcb panel, pots, knobs, jacks, components (ics, resistors caps etc) a 3x2 header for cortex and a ribbon cable for the rgb expander header.


@creatorlars Im gonna do a second flavor of the expansion with YUV outs. Was wondering if I can use the Lumma circuit that you kindly show me as the Y

or I must do another new lumma signal (I was going to go with voltage dividers of R G and B)
Y = 0.299R + 0.587G + 0.114B

My real question is if the Lumma of the YUV is different to the Luma schematic. Luma YUV vs Luma RGB (I would say no, but I’m in doubt.).

This lumma circuit is magix!


Great work on this @luix! I’m down for two kits. Curious as you’re planning a second breakout … could they easily be combined into one expander?

yeah should be easy to chain them.


@luix That circuit should work fine! For the U and V outputs you can follow a similar method. I generally use SPICE simulations to tweak circuits like this until output voltage readings are correct according to RGB input voltages. 5Spice has a free version we’ve used for years, although I’m using Tina more frequently now.

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I’d be down for a kit to support the project. My cortex already has expansion headers soldered :slight_smile:


I’ll probably want a PCB+panel at least. Wasn’t planning on getting a visual cortex, but I’ve run into a dead end trying to troubleshoot my cadet sync generator build–so I should probably just buy a vc.

Sign me up for one too!

I’ve been running the VC component output back into its Input Decoder, and then out from those 1v RGB outputs into the MemPal. Not so ideal, of course, as I lose that component input. :-/

I’d like to get a kit or prebuilt as well. This is a great project, thanks!

Def. in for a panel/pcb when you are ready to take orders :slight_smile:


I am in for this! Would take a kit, or panel/PCB, or built version.

I’d be interested in panel+pcb or kit! YUV version would be great too - any chance to combine them, or will they be separate exapnders?

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right! I would absolutely go for the dual if it was an option

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I started to lay the PCB for the YUV version, but decide to first finish this run of pcbs test them, prepare kits, and a solder prebuilt modules and then will do the YUV.

Both will be compatible and can be used at the same time since they read from the RGB expansion bus of the Visual Cortex

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Sounds absolutely reasonable. I am definitely still interested also in a single RGB version!

I’ve just got home and the postman had a surprise, and I remembered a quote from a famous American movie:

Life is like a box of pcbs and panels, you never know what your gonna get.
-Forest Gump

So final version pcbs (will double check them again everything is fine) and PANELS arrived.

This red panels are in honor to all LZX Cadets :raised_hands:

@pbalj now caps are nicely placed, thanks for the suggestion I completely forgot about it.

Panels fit perfect on previous pcb (which is same footprint as the new one) there will be 2mm Red PCBPanel and 2mm Black aluminium panels. I don’t know if I should give the option to chose or just include both on every kit…

I still need to get to details to costs on kits and built modules, but will probably target at 50€-60€ for kits and 70€-90€ for built modules (plus shipping from Spain probably 6€-15€ depending if you are EMEA or Mericaaa). After all kits are sold I’ll sell spare pcbs :).

So my next steps will be to check everything is fine with the pcb, if so I’ll probably send a Google Form in this thread so all of you can write which ones and how many kits/modules you will want.

After the form is closed I’ll be able make the order of the parts to Mouser (so 3 days) and then I’ll ask you within those days to send me a PayPal.

Ill keep you all informed, I’m very excited on this project because its a community project for the LZX community. :heartbeat::heartbeat::heartbeat::heartbeat:


Updates on this, the board works as expexted, it as two minor bugs I’ll fix for the final version (pots are inverted, so positive signal should be from 12’ to 5’ (clockwise) and inverted signal from 12’ to 7’ (counterclockwise), second bug is that the color pins are swaped so Red is Blue and Blue is Red. in the video you can see how I patch a V ramp to the Byle and output that on the expander Red’s output.

One thing I wanted to ask on this thread for all your consideration and feedback is the following. When the attenuverter inverts the signal which is 0v to 1v DC from VC it outputs a 0v to -1 (inverted duh)… but the standard video signal is always 0v to 1v, so the inverted signal is not super usefull unless you use the AC switches or you invert it back or add a offset of 1v.

My question is, does it make sense and is useful for you to have an inverted (-1v) signal? Or should I replace the attenuverter with a attenuator (just attenuate from 0v to 1v and not invert). I’m scratching my head on which use case would be more useful for most ppl. I think there are use cases for both but what the vidiots think?

Maybe the best solution is to add 1v to the inveted signal, so its always 1V regardless if its inverted or not?

I’m asking all this for the first time when I actually plugged it and started to use it on different parts of my system.


It might be handy to have the inverted signal available for summing with a positive voltage. I don’t see much downside to using an attenuverter.