Risks running JAMMA RGB to modern VGA or SCART>YPbPr adapter

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BazookaBen
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Risks running JAMMA RGB to modern VGA or SCART>YPbPr adapter

Post by BazookaBen »

So my cousin is going to try to swap in a CRT chassis from a stand TV into his NeoGeo cab.

I told him he could grab any RGB>Component converter off the internet, but then I realized that JAMMA outputs higher voltages for RGB than either VGA or SCART. And also higher voltage on Sync than SCART.

So, are products like Retrotink's RGB2COMP able to auto-adjust to these levels, or would the RGBS signals need resistors in series to look correct?

Also, how likely is actual damage to occur to any of these adapters with a raw TTL RGB signal?

I'm just a little confused because on my Audio Authority 9A60 I'm able to feed both console and PC RGB signals, and it works fine (don't own any arcade hardware to test with it). Though in my understanding sync is the only signal that has a different voltage between the two types.
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maxtherabbit
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by maxtherabbit »

JAMMA RGB voltage is higher than SCART yes but it's not TTL either

I don't think any SCART input device will cope with the levels without attenuation

I'd recommend using GBS-control setup for component output
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BazookaBen
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by BazookaBen »

I think we should try to avoid going analog>digital>analog when we can keep it analog>analog

But yeah, I'm also curious about VGA input devices like the one from Linuxbot3000.
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maxtherabbit
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by maxtherabbit »

BazookaBen wrote:I think we should try to avoid going analog>digital>analog when we can keep it analog>analog

But yeah, I'm also curious about VGA input devices like the one from Linuxbot3000.
Ordinarily I'd agree with that sentiment, however experience has taught me that analogue domain transcoders generally suck balls
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kitty666cats
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by kitty666cats »

I’m almost certain that both of linuxbot’s RGB to YPbPr’s should be fine with any sync voltage between 0.7Vpp and 5V…? I will report back to y’all about this
nes.og
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by nes.og »

RGB2COMP was not designed for TTL levels so you would want to use resistors.

Here is some info about using GBS Control with arcade boards levels:

https://github.com/ramapcsx2/gbs-contro ... ade-Boards

Another option is the Jrok which will support Jamma voltage levels and also transcode to YPbPr:

https://www.jrok.com/hardware/RGB.html

So it is possible to transcode from RGB to YPbPr colorspace using opamps without digital processing?

I imagine there is other info/options noted in the Super Gun thread.
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kitty666cats
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by kitty666cats »

nes.og wrote:RGB2COMP was not designed for TTL levels so you would want to use resistors.

Here is some info about using GBS Control with arcade boards levels:

https://github.com/ramapcsx2/gbs-contro ... ade-Boards

Another option is the Jrok which will support Jamma voltage levels and also transcode to YPbPr:

https://www.jrok.com/hardware/RGB.html

So it is possible to transcode from RGB to YPbPr colorspace using opamps without digital processing?

I imagine there is other info/options noted in the Super Gun thread.
Yeah, the Kramer FC-14 is a good example (RE: analog… or rather, ‘as analog as possible’ circuitry. I also have a Faroudja bi directional RGB <-> component transcoder with some insanely excessive circuitry haha

From what I gathered Jam (linuxbot) indicated his SCART transcoder would be better In this use case…? Gotta make sure to have proper attentuated cables before the transcoder though
nes.og
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by nes.og »

kitty666cats wrote:Yeah, the Kramer FC-14 is a good example (RE: analog… or rather, ‘as analog as possible’ circuitry. I also have a Faroudja bi directional RGB <-> component transcoder with some insanely excessive circuitry haha

From what I gathered Jam (linuxbot) indicated his SCART transcoder would be better In this use case…? Gotta make sure to have proper attentuated cables before the transcoder though
Interesting, thanks for sharing.

Looks like the J-Rok attenuates and has connectors that can be easier to interface with Jamma. It also has pots to adjust the RGB levels. I know that Linuxbot makes good stuff and you could also use his RGB VGA to YPbPr Component unit which also accepts RGBS then then splice the JAMMA wires to a VGA cable if you don’t want to use SCART. I imagine his unit is made for 0.7 volt RGB so probably need to add the resistors. Of course you could also use the the Retrotink transcoder with SCART and attenuate that as well.

Audio will need to be attenuated as well which could run through one of the SCART units or separate.
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kitty666cats
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by kitty666cats »

nes.og wrote:
kitty666cats wrote:Yeah, the Kramer FC-14 is a good example (RE: analog… or rather, ‘as analog as possible’ circuitry. I also have a Faroudja bi directional RGB <-> component transcoder with some insanely excessive circuitry haha

From what I gathered Jam (linuxbot) indicated his SCART transcoder would be better In this use case…? Gotta make sure to have proper attentuated cables before the transcoder though
Interesting, thanks for sharing.

Looks like the J-Rok attenuates and has connectors that can be easier to interface with Jamma. It also has pots to adjust the RGB levels. I know that Linuxbot makes good stuff and you could also use his RGB VGA to YPbPr Component unit which also accepts RGBS then then splice the JAMMA wires to a VGA cable if you don’t want to use SCART. I imagine his unit is made for 0.7 volt RGB so probably need to add the resistors. Of course you could also use the the Retrotink transcoder with SCART and attenuate that as well.

Audio will need to be attenuated as well which could run through one of the SCART units or separate.

Sounds like you know what you’re doing and have several options ;)

There’s also that GreenAntz one but tbh a JROK may be best in this scenario
nes.og
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Re: Risks running JAMMA RGB to modern VGA or SCART>YPbPr ada

Post by nes.og »

kitty666cats wrote:Sounds like you know what you’re doing and have several options ;)

There’s also that GreenAntz one but tbh a JROK may be best in this scenario
I’m not an expert by any means. Just a few ideas I could think of. I can’t vouch for the Jrok, just something I came across. I’m sure there are a fair amount options out there.
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