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VGA video amplifier board for Arcade Monitor with sync filter

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njz3

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Hello everyone,

I present you a new realization made by people at gamoover french forum : a video amplifier board made to simplify the swap between a stack/pcb and a PC with VGA output which would be placed in a cabinet with an original arcade monitor.
VideoAmpV1_recto.jpeg

The board is a video amplifier with out-of-range frequency filtering to protect the chassis of the monitor. It creates a video csync signal with wide chassis compatibility (Nanao, Hantarex, Sony TV have been tested), and it emulates a display identification signal of a 15/24/31kHz monitor with some super-resolutions at the VGA level (EDID), so you don't need any AMD specific driver, or to tweak with the output frequencies with Custom Resolution Utility. It remains AMD/Calamity compatible, but also opens up compatibility with Intel and NVIDIA cards in a plug-and-play manner.
In addition, there is a SCART RGB output if you ever need to put a 15kHz CRT TV in place of your original arcade monitor that sadly gave up a few years ago.
The only constraint is to have an Intel/NVIDIA/AMD graphics card with a native VGA port to benefit from the automatic display identification. Otherwise, you'll have to go back to the Calamity AMD driver and you'll only benefit from the video amp, csync and protection filtering.

The board also allows to emulate a basic keyboard with just 5 keys for those who want to complete their wiring already done with a hackpad and who are looking for a way to add the TEST/SERVICE/MENU/etc. buttons.
It's basically the same as a jammasd without the jamma connector and less emulated keys.
For those who are interested or for more details, please have a look to the topic on gamoover forum here https://www.gamoover.net/Forums/index.php?topic=44224.0

Edit: you can find the "Readme.pdf"
https://drive.google.com/file/d/1Oq9VBSkhZ66eSoXLy9zjRUQlKemMLN0S/view?usp=share_link
 
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One beta-tester has made a comparison between real stack VS an intel laptop computer pluggued with the VideoAmp board (no specific driver installation) on a Nanao MS9 monitor.
The monitor pot's have not been touched after swapping the stack and the computer. Enjoy.
 
Google translate is not translating all the replies properly. Firstly, awesome project!!! Is this an opensource project?
 
RealMFnG said:
Google translate is not translating all the replies properly. Firstly, awesome project!!! Is this an opensource project?
Click to expand...
No, the embedded code and the pcb are not open source.
If you have any question I can answer them as I am the developper of the firmware and the PC companion app.
 
Ok, I see the only input is VGA.
  • Does this lock this device to RGBHV or is RGBS possible?
    • If RGBS is possible, which pin on the DSUB connector carries the CSync signal?
    • on output via VGA and SCART, is it RGBS or RGBHV? is there a way to switch from either or?
  • I am unsure if this device does any transcoding of video rsesolution
    • Seems you are allowing non-15khz video to be inputted for display on 15khz monitors
    • How are the dips handling any transcoding?
  • I am assuming everything is powered off of 5vdc going into the Arduino, correct? Nevermind, I see a 5vdc terminal
And I doubt you will answer this, but what commercially available video amp are you using out of curiosity?
 
RealMFnG said:
Ok, I see the only input is VGA.
Click to expand...
Yes
RealMFnG said:
  • Does this lock this device to RGBHV or is RGBS possible?
Click to expand...
RGBHV only right now. We were looking for Scart input (using an LM1881), but it was tricky to get all kind of inputs (PAL/NTSC) working.
RealMFnG said:
    • If RGBS is possible, which pin on the DSUB connector carries the CSync signal?
Click to expand...
See above
RealMFnG said:
    • on output via VGA and SCART, is it RGBS or RGBHV? is there a way to switch from either or?
Click to expand...
VGA out is only a passthrough for EDID emulation signals (in this case it is more or less what a programmable EDID emulator does).
In particular it is used to generate a signal for 240p@120Hz easily.
Edit: for SCART it is RGB+Csync.

RealMFnG said:
  • I am unsure if this device does any transcoding of video rsesolution
Click to expand...
No, it does not.

RealMFnG said:
    • Seems you are allowing non-15khz video to be inputted for display on 15khz monitors
Click to expand...
No. The board will actually do the same as the AMD/Calamity combos by overloading the EDID (display information) to force your computer and video graphics board to generate true video signals at 15/24/31kHz using standard super-resolutions like 1280x240p, 1024x384p (or 1024x768i), 640x480, etc...

RealMFnG said:
    • How are the dips handling any transcoding?
Click to expand...
No transcoding is done. This is simply a video amplifier with an embedded EDID emulator.
RealMFnG said:
  • I am assuming everything is powered off of 5vdc going into the Arduino, correct? Nevermind, I see a 5vdc terminal
And I doubt you will answer this, but what commercially available video amp are you using out of curiosity?
Click to expand...
After trying different amplifiers, we picked the THS7375 as it gives a very nice and colored picture on most arcade chassis we tried.
 
njz3 said:
VGA out is only a passthrough for EDID emulation signals (in this case it is more or less what a programmable EDID emulator does).
In particular it is used to generate a signal for 240p@120Hz easily.
Edit: for SCART it is RGB+Csync.
Click to expand...
So irregardless of the video resolution input up to VGA, the EDID emulator forces 240p output?
 
RealMFnG said:
So irregardless of the video resolution input up to VGA, the EDID emulator forces 240p output?
Click to expand...
I guess I am not clear.
When the board is pluggued to your VGA graphics adapter, the EDID emulator will reports that your "monitor" is a 1280x240p (15kHz) resolution display for example, which will enforce your computer/GPU to output such a resolution with 15kHz frequency.
This is the same as GroovyMAME or Calamity, but it is not done on the computer side, but on the board side.
I attach the readme (within the archive) in the first post so that you can have more details.
 
njz3 said:
I guess I am not clear.
When the board is pluggued to your VGA graphics adapter, the EDID emulator will reports that your "monitor" is a 1280x240p (15kHz) resolution display for example, which will enforce your computer/GPU to output such a resolution with 15kHz frequency.
This is the same as GroovyMAME or Calamity, but it is not done on the computer side, but on the board side.
I attach the readme (within the archive) in the first post so that you can have more details.
Click to expand...
Wowsers! That is a spectacular solution!!!!

Please allow me to be a beta tester!
 
We have finished the beta test. May I ask you what monitor you have?
If you want a board we can send one to you but the shipping to your place will be overkilled compared to the price of the board itself. I really don't know how to manage that.
 
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njz3 said:
We have finished the beta test. May I ask you what monitor you have?
If you want a board we can send one to you but the shipping to your place will be overkilled compared to the price of the board itself. I really don't know how to manage that.
Click to expand...
I have just about all of them.
  • Nanao MS9, MS2930, MS2933
  • Sanwa PFX
  • Wells Gardner K7000, K7400, K4900, K4600
  • Electrohome G07
  • Neotech 25" (forget the model number)
  • A few more that don't come to mind right now, including 12" monitors for classics
Video amping is a fave topic of mine. But yeah, I'll just keep this project in mind.
 
Just some fresh info regarding monitor identification (EDID) and 15kHz/24kHz signal.
As suggested in GroovyArcade wiki, I tried a DisplayPort to VGA adaptor with EDID passthrough and the result is that it perfectly works with my Nvidia 1060. The board was automatically detected by Windows 10, and setting low pixel clocks resolutions like 320x240p@60Hz worked out of the box giving a 15kHz signal. Same worked for 24kHz signals.
 
It is almost available, we just started a first batch.
Send me a personnal message.
 
I got some questions from GumGum that I will answer here so that it is shared for everybody.

GumGum said:
If I don't use Emucrt driver, how would it be possible for me to create custom modelines (custom resolution) that will match the native resolution of each game?
Click to expand...
This is not yet possible.
If you want to do that, you would still need some tools like Emucrt to tweak the video refresh rate or the vertical resolution (208p, 224p, etc.) to exactly match your native game video signal.

Basically the board will report itself as a 15kHz (or 24kHz or 31kHz) CRT monitor with a unique preferred resolution using EDID identification through the VGA port. This is purelly hardware-based and do not need any specific software or driver on your computer.
So far, I only report 1 resolution at a time (add its interlaced alternative) so that the PC operating system (Windows, Mac or Linux) will be enforced to output such resolution.
If you download the companion App from the link below and run "VideoAmp.exe", you will see the list of available EDID.
https://drive.google.com/file/d/1ZzmloYyj6wAB0Dx-oAT1t-D87Z3fXOPz/view?usp=share_link

Most specifically, among the 15kHz resolutions you will find super-resolutions like 1280x240p or 1920x240p, which means you will need to pass a horizontal stretch parameter of 4:1 or 6:1 to your emulators to correct the aspect ratio.
In case you pick a low pixel clock resolution like 320x240p (below 20MHz pixel clock), please be aware that some GPU/boards will crash instantaneously your computer !
In this case, disconnect the VGA, reconfigure the board with a wider resolution on another computer, then try again.
To force a refresh of the EDID, you need a "unplug"-"replug" operation on the vga socket or use special tools like "restart" from CRU to perform a hot-plug.

GumGum said:
I would be happy to not worry about emucrt driver because emucrt driver only works in Windows 10 Safemode.
Click to expand...
You will definitly appreciate the VideoAmp board mainly due to its "plug and play" nature and simplicity.

When time permits, I will look into adding custom profiles to the videoamp companion app, so that you would be able to switch to your customs resolutions. I just need to understand how to generate the 18bytes EDID preferred resolution from a standard modeline written in a text file.
Still, there will be some need for tools to perform the reload of the EDID from the board (like performing a hot-plug).
 
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njz3 said:
When time permits, I will look into adding custom profiles to the videoamp companion app, so that you would be able to switch to your customs resolutions. I just need to understand how to generate the 18bytes EDID preferred resolution from a standard modeline written in a text file.
Click to expand...
Definitely need the feature to add in custom EDID preferrerd resolution because lots of games have their own resolution. I love the idea that it's all hardware based and no need to install any extra driver for the pc.
 
A beta tester also tried some recent Teknoparrot games using a GTX960 with displayport to VGA converter with EDID set at 512x384p, on a 24kHz nanao MS9.
Some games can work at such a low 4/3 resolution, but other cannot be streched... Below is Initial D 8 infinity
Would love that some Teknoparrot modders can add some video patches to add 4/3 lowres resolutions !
 
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Some fresh news from the scart output of the VideoAmp board.
A user reported that the super resolution EDID perfectly works with VGA output of an Intel IGP of a 4th gen i5 plugged to a Sony CRT TV with RGB scart input :
And on a PVM 9L3 (tate rotation) :
 
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