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Custom RGBS and Audio Switch

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I am trying to design a custom rgb video/audio switch. Mainly for Retro video game console connected to a PVM style monitor.
It will also control my monitor via wired remote control for input selection and tally light :D.

Other switcher were considered. Scart in the US seems to be an expensive hassle with many adaptors.  Extrons need custom sync stripping bnc cables that seem difficult to make, both because of the bnc connectors and sync stripping. If this custom switch idea does not work out an Extron is the next choice. Using component and rgb alternating on this monitor involves a switch on the rear of the monitor. Which is mounted in a server rack. This makes component a poor choice.  Most premade cables are on backorder.

I have never built anything like this so any and all help is appreciated.

Chip Selection
I was thinking about this for rgb video https://datasheets.maximintegrated.com/en/ds/MAX4887.pdf

And this for Composite Sync and audio 4751 https://datasheets.maximintegrated.com/en/ds/MAX4751-MAX4753.pdf

Db15 for the inputs using custom cables.
Parts for an example cable.




Mounted in a 2u rack case.

Attached is a prototype design. Made in kicad

Prototype is for three inputs, final will have ten.
Prototype does not have the tv control.
Prototype uses db15 for output. Final will use db15hd for video output and something else for audio output.
Final will have a separate panel for input selection. Possibly an Arduino with a display for input labeling, with a custom design anything is possible.

Ground and power planes what should they be like?
I know I need some capacitors right?
Am I using vias and planes correctly?
Power circuit? on board ac? external dc?
Are these chips good choices?
Any special note about clearances for the db connctors?
Board layout?
Rca connections in footprints in kicad?

Thanks Again

Worked on version 1.1 of the prototype design.

-Changed video out to db15hd for this style cable https://www.monoprice.com/product?p_id=568

-Added separated audio out (RCA)

-Fixed potential problem if device on first input is turned on when an another input is active then the signal would overlap. Added another max4751 before second input.

-Removed switch. Input control TBD.

-added temporary power connector.

Which package version of the chip should I use?

You're going to have to capacitively couple and bias the audio.
The 4751 does not go below ground.

Thank You!

I think the sync (composite video) would have the same problem.

Would these chips work without coupling?




The 4529 is a "T" switch, a much better switch than the normal "SPST" CMOS switches.
It also goes for $3 in single units.

You've got 4 different signals:
[*]RGB = 0 to 0.7
[*]HV = TTL
[*]Composite = -0.3 to 0.7
[*]Audio = ~ -0.5 to 0.5[/list]

With the RGB & composite you have to watch for crosstalk.
Especially since your sources aren't synced.
A good layout and the 4529 will certainly do the job, but is it overkill?

Do you really want to bundle the RGB and composite?
No device is going to put out both (and if they did you'd just take the RGB).

I dunno, wouldn't you just modify anything composite with an RGB output?
That seems easier/better to me.


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