Simple RGB to YPbPr Module

[mikechi2]

Second post of the day! Also wanted to share some results on building a super simple RGB to component transcoder circuit. It's basically straight from the Linear Technology app note:

http://www.analog.com/media/en/technica ... an57fa.pdf



Turned it into a module here. Super small and best of all - no electrolytic coupling caps. I really hate those things. Module is mounted on a larger PCB with a SCART input jack and RCA output jacks. Larger board also has a LM1881 sync stripper to provide a clean CSYNC signal for insertion back into the luma output later on. Test setup is pretty simple - I'm using a RGC SCART cable and a 3-wire modded SNES mini. Using my PVM-14L5 for monitoring and then looping into my scope for measurement.



Here's comparison of the module versus the HDRV cables, set to low brightness. Pretty much spot on -- the gain is just tiny fraction lower than the HDRV but these things are easy to adjust out on your monitor.



Not sure if I want to build a stand-alone converter but good to prove out the circuit design from the app note!

[maxtherabbit]

That's badass man, if you could sell this around the $50 price point and/or offer it as an affordable add on to the 2x you would really have something outstanding

[energizerfellow‌]

I agree there's a market for these and it's worth selling. I love how simple it is.

Layout-wise, the phono jacks could use better spacing (use A/V-labeled 3+2 jack blocks?). I'd also put the output jacks and power input at 90 degrees from the notched side of the SCART socket so the SCART plug's right-angle cable exist makes the physical layout "pass-though" like a laptop power brick.

Any preferences on SCART coming in from the top or side? Time for power over a USB Type-C connector? Small enough to fit inside a SCART hood and run off the +5v (to +12v?) from the SCART source's pin 8? Sync-on-green support (for the PS2)?

If it can fit in a SCART hood, using a HD Retrovision-style one-piece YPbPr+audio A/V cable coming out of a SCART connector would be awesome. You'd need to offer both a male and female SCART version for switch-to-display and console-to-display. Offering lengths of 1m/3' and 2m/6' would be nice as well.

[nmalinoski]

I'd like to see a version of this with a DE-15 input, or maybe even BNC, for taking RGBS from an Extron CrossPoint, VGA switch, or RGB interface without needing a $45-$50 SCART adapter.

And, on that note, will the LM1881 take TTL sync?

Would be neat if this design could fit into the footprint of one of those SCART-head-sized boards; then we could have RGB SCART->YPbPr component/RCA adapters. They'll still need external 5V, though; can't count on any line in a SCART cable supplying exactly 5V.

[mikechi2]

Thanks guys and all good ideas! I like the idea of putting this into a SCART head with RCA outputs plus a jack for power...

From what I can see, the LM1881 takes TTL sync fine, but it's running out of spec, so I wouldn't want to put it into a product without some sort of clamp. Might make another version just for VGA sources with a precision HV sync combiner.

[energizerfellow‌]

Thanks guys and all good ideas! I like the idea of putting this into a SCART head with RCA outputs plus a jack for power...

I think a short female USB dongle coming out of the SCART hood would look cleaner and be easier to make than cutting holes in a SCART hood, assuming you can get that much cabling out of the hood.

If you're open to chip suggestions, check out the ISL59885 instead of the LM1881/EL1883. I've seen a number of reports that the LM1881 can bend images slightly and the ISL59885 is just plain more modern with a cleaner, faster output that kills Macrovision. The ISL59885 can be found in the HAS supergun, for instance. If you want a fun bonus side project, the ISL59885 has a detect pin for >25khz sync, so you could create an automatic video switch that selects between a standard/medium resolution csync output or HV-sync EDTV/HDTV output depending on input video signal.

Also look into doing Retro Gaming Cables style SCART head stickers. It not only looks nice and a chance to place your logo, but it's also a good place to say it's a directional active cable for RGBs 1Vp-p signals.

I'd take a 6' one with a male SCART end and male RCA connectors for SCART switch to component display.

I'd like to see a version of this with a DE-15 input, or maybe even BNC, for taking RGBS from an Extron CrossPoint, VGA switch, or RGB interface without needing a $45-$50 SCART adapter.

And, on that note, will the LM1881 take TTL sync?

Would be neat if this design could fit into the footprint of one of those SCART-head-sized boards; then we could have RGB SCART->YPbPr component/RCA adapters. They'll still need external 5V, though; can't count on any line in a SCART cable supplying exactly 5V.

This should be it's own standalone product with female DB15 connectors on both ends and external power. Use whatever specialized cables you need for adapting to things like BNC or JAMMA-style JST video connector. Having a buffer/regen switch for sync control around a ISL59885 might be a good idea.

Given how variable everything is, at a minimum you'd need independent switching for the following, ideally on both the input and output sides:
- 75 ohm vs 1k/500 ohm termination
- TTL vs 1Vp-p signal
- RGBHV vs RGBS vs RGsB sync

[James-F]

I hate these microUSB power connectors, a barrel plug is much sturdier.

[nmalinoski]

I hate these microUSB power connectors, a barrel plug is much sturdier.

The problem with barrel plugs is that people are stupid. Center-positive, center-negative, 12V, 9V, 3V--it's all the same to some people, which has led to people blowing their OSSCs or gscarts (I forget which takes a 12V PSU). USB at least operates at 5V across the board. I agree that MicroUSB is garbage, but I would not want a barrel plug; I think MiniUSB is a good compromise.

[energizerfellow‌]

I agree that MicroUSB is garbage, but I would not want a barrel plug; I think MiniUSB is a good compromise.

At this point it's probably best to go for USB Type-C instead of MiniUSB/MicroUSB as the connector is more sturdy and there's less for the consumer to screw up considering it's reversible. It's also been common enough, long enough that people probably have cables kicking around at this point and parts are getting cheap and easy to come by. Using a short female dongle instead of a jack will also help keep people from using brute force to break free jacks from the board.

[James-F]

That's partially true.
A halfwit does not care about RGB nor can handle the OSSC.

[muggsy]

As the seller is from NZ I grabbed a couple off Trademe (NZ equivalent of Ebay)

Now I just need to find some component CRTs to add to my collection

For the moment I'll use thru my ossc (redundant I know)

[maxtherabbit]

Thanks guys and all good ideas! I like the idea of putting this into a SCART head with RCA outputs plus a jack for power...

From what I can see, the LM1881 takes TTL sync fine, but it's running out of spec, so I wouldn't want to put it into a product without some sort of clamp. Might make another version just for VGA sources with a precision HV sync combiner.

I would recommend replacing the LM1881 with the LMH1980 for the RGBS version, and if you choose to make a RGBHV version I would recommend a sync combiner that can handle 31kHz

480p is easily within the bandwidth of the transcoder circuit, so if you account for it on the sync circuit you open up compatibility with modded PS2s on the RGBS side and dreamcasts on the RGBHV side

I know that doesn't matter for use with your 2x, but it would make the device more versatile

[mikechi2]

Out of curiosity, why wouldn't you just set the PS2 to output component natively as opposed to forcing RGB then transcoding?

[nmalinoski]

Out of curiosity, why wouldn't you just set the PS2 to output component natively as opposed to forcing RGB then transcoding?

Only big reason I can think of would be for easier integration into RGB SCART setups. As far as I know, with a quality component cable, YPbPr output from the PS2 is indistinguishable from RGB, and it avoids the RGsB problem altogether; but it often isn't compatible with or doesn't make sense to use it with the SCART equipment that many people already have.

People may prefer to use RGB SCART cables and switchers, because it's what's commonly used for RGB in the retro gaming community, and then use an RGBS->YPbPr transcoder at the very end of their chain, because their US-market TVs don't support SCART, or can't handle 15kHz RGB over VGA, or they bought a RetroTINK 2X for HDMI conversion over a more expensive OSSC or Framemeister.

[maxtherabbit]

Out of curiosity, why wouldn't you just set the PS2 to output component natively as opposed to forcing RGB then transcoding?

Only big reason I can think of would be for easier integration into RGB SCART setups. As far as I know, with a quality component cable, YPbPr output from the PS2 is indistinguishable from RGB, and it avoids the RGsB problem altogether; but it often isn't compatible with or doesn't make sense to use it with the SCART equipment that many people already have.

People may prefer to use RGB SCART cables and switchers, because it's what's commonly used for RGB in the retro gaming community, and then use an RGBS->YPbPr transcoder at the very end of their chain, because their US-market TVs don't support SCART, or can't handle 15kHz RGB over VGA, or they bought a RetroTINK 2X for HDMI conversion over a more expensive OSSC or Framemeister.

pretty much this, personally I do have my PS2 set to output component natively and it is beautiful through HDRV cables

but I keep hearing how people want to have everything run through the same SCART switch etc.

[mikechi2]

Out of curiosity, why wouldn't you just set the PS2 to output component natively as opposed to forcing RGB then transcoding?

Only big reason I can think of would be for easier integration into RGB SCART setups. As far as I know, with a quality component cable, YPbPr output from the PS2 is indistinguishable from RGB, and it avoids the RGsB problem altogether; but it often isn't compatible with or doesn't make sense to use it with the SCART equipment that many people already have.

People may prefer to use RGB SCART cables and switchers, because it's what's commonly used for RGB in the retro gaming community, and then use an RGBS->YPbPr transcoder at the very end of their chain, because their US-market TVs don't support SCART, or can't handle 15kHz RGB over VGA, or they bought a RetroTINK 2X for HDMI conversion over a more expensive OSSC or Framemeister.

pretty much this, personally I do have my PS2 set to output component natively and it is beautiful through HDRV cables

but I keep hearing how people want to have everything run through the same SCART switch etc.

Thanks for explaining... maybe what you really need is a SCART switch with a dual YPbPr output...

[Classicgamer]

Why not just buy a JROK?


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


I have one. It does a decent job. I used to use it to convert rgb from my 240p mame box to component and SVideo for use on a Sony Trinitron tv.

Unless your time is worth nothing, it's probably the more economical solution vs building one from scratch.

At the least, maybe you could just copy their design to save time?

[nmalinoski]

Why not just buy a JROK?


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


I have one. It does a decent job. I used to use it to convert rgb from my 240p mame box to component and SVideo for use on a Sony Trinitron tv.

Unless your time is worth nothing, it's probably the more economical solution vs building one from scratch.

At the least, maybe you could just copy their design to save time?

The JROK doesn't satisfy everyone's needs. Just by glancing at it, it looks like it's primarily for arcade use; it lacks anything recognizable as a standard video input or power connector to most people who are looking for something like this for use with a console. If you're buying this, it looks like you'll need to figure out how to adapt your SCART or DE-15 cables, as well as 5V power, mounting, and a case all on your own. On top of that, this thing costs about $82 USD, and only supports 15kHz video.

For similar cost, you can get the ShinyBow SB-2840, which comes in a metal case, supports 15kHz and 31kHz (480p), has a SCART input and RCA outputs for YPbPr component and stereo audio, and comes with a wall wart PSU.

Or, for $50 USD, you can get that transcoder from New Zealand. Although lacks a case, and it's not clear whether it supports greater than 15kHz video, it has the same I/O connectors as the ShinyBow and uses common MicroUSB for power.

What's neat about the proposed module is that it's extremely simple; it doesn't rely on any electrolytic capacitors (which tend to leak after a number of years or when exposed to a lot of heat), it sounds like it could handle everything from 240p to 1080p, and its simplistic design has the potential to fit into a SCART head, which means the potential for premade, inline SCART/DE-15 RGB to YPbPr component converters--no exposed PCBs, no fabrication required by the buyer, recognizable and common USB for power, and it can probably hit a sweet spot between $40 and $60 (depending on things like parts cost, labor, and popularity). (And no, I'm not telling Mike Chi how to price his devices. )

I think most of us are trying to connect RGB-capable game consoles to YPbPr-capable consumer CRTs, not so much arcade boards; so the JROK simply doesn't make sense when products like the SB-2480 or the NZ transcoder are readily available and Mike Chi's is coming in the relatively near future, all at or around the same price and all simply working out of the box with RGB SCART.

[maxtherabbit]

if I have to email someone for pricing it aint happening, leave that shit in 1998

[nmalinoski]

if I have to email someone for pricing it aint happening, leave that shit in 1998

Prices were posted on the one distributor website I checked; but yeah, just give me a PayPal cart and be done with it.

[mikechi2]

Why not just buy a JROK?


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


I have one. It does a decent job. I used to use it to convert rgb from my 240p mame box to component and SVideo for use on a Sony Trinitron tv.

Unless your time is worth nothing, it's probably the more economical solution vs building one from scratch.

At the least, maybe you could just copy their design to save time?

The JROK doesn't satisfy everyone's needs. Just by glancing at it, it looks like it's primarily for arcade use; it lacks anything recognizable as a standard video input or power connector to most people who are looking for something like this for use with a console. If you're buying this, it looks like you'll need to figure out how to adapt your SCART or DE-15 cables, as well as 5V power, mounting, and a case all on your own. On top of that, this thing costs about $82 USD, and only supports 15kHz video.

For similar cost, you can get the ShinyBow SB-2840, which comes in a metal case, supports 15kHz and 31kHz (480p), has a SCART input and RCA outputs for YPbPr component and stereo audio, and comes with a wall wart PSU.

Or, for $50 USD, you can get that transcoder from New Zealand. Although lacks a case, and it's not clear whether it supports greater than 15kHz video, it has the same I/O connectors as the ShinyBow and uses common MicroUSB for power.

What's neat about the proposed module is that it's extremely simple; it doesn't rely on any electrolytic capacitors (which tend to leak after a number of years or when exposed to a lot of heat), it sounds like it could handle everything from 240p to 1080p, and its simplistic design has the potential to fit into a SCART head, which means the potential for premade, inline SCART/DE-15 RGB to YPbPr component converters--no exposed PCBs, no fabrication required by the buyer, recognizable and common USB for power, and it can probably hit a sweet spot between $40 and $60 (depending on things like parts cost, labor, and popularity). (And no, I'm not telling Mike Chi how to price his devices. )

I think most of us are trying to connect RGB-capable game consoles to YPbPr-capable consumer CRTs, not so much arcade boards; so the JROK simply doesn't make sense when products like the SB-2480 or the NZ transcoder are readily available and Mike Chi's is coming in the relatively near future, all at or around the same price and all simply working out of the box with RGB SCART.

Alright here it is... all fitted into a SCART head and still no electrolytic caps!



I'll build a few of these and see if we can get this little guy in the $40 to $60 range

[energizerfellow‌]

Alright here it is... all fitted into a SCART head and still no electrolytic caps!

itshappening.gif

There was much rejoicing.

Still using a ISL59885, right? Is a stripper circuit technically required or just a nice to have?

[maxtherabbit]

that's sexy dude

[energizerfellow‌]

To cut down on variants come product time, how about a 18"/500mm female SCART and 3'/1m male SCART versions? The female is a dongle for hanging off the back of a display or receiver and the male is for switch->receiver/display. Both with male RCA connectors.

Variants of these, basically:
https://www.retrogamingcables.co.uk/aud ... m-monitors
https://www.retrogamingcables.co.uk/aud ... rter-cable

[nmalinoski]

To cut down on variants come product time, how about a 18"/500mm female SCART and 3'/1m male SCART versions? The female is a dongle for hanging off the back of a display or receiver and the male is for switch->receiver/display. Both with male RCA connectors.

Variants of these, basically:
https://www.retrogamingcables.co.uk/aud ... m-monitors
https://www.retrogamingcables.co.uk/aud ... rter-cable

Why not just the short female SCART to male component and use a male to male SCART cable between the adapter and the switch?

[energizerfellow‌]

Every extra electrical connector is a potential failure point, electrical loss, or electrical noise point, especially in the analog domain. Connector insertion loss is a thing. You want runs to be as short as possible with as few connectors as possible.

[samson7point1]

Why not just buy a JROK?


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


I have one. It does a decent job. I used to use it to convert rgb from my 240p mame box to component and SVideo for use on a Sony Trinitron tv.

Unless your time is worth nothing, it's probably the more economical solution vs building one from scratch.

At the least, maybe you could just copy their design to save time?

The JROK doesn't satisfy everyone's needs. Just by glancing at it, it looks like it's primarily for arcade use; it lacks anything recognizable as a standard video input or power connector to most people who are looking for something like this for use with a console. If you're buying this, it looks like you'll need to figure out how to adapt your SCART or DE-15 cables, as well as 5V power, mounting, and a case all on your own. On top of that, this thing costs about $82 USD, and only supports 15kHz video.

For similar cost, you can get the ShinyBow SB-2840, which comes in a metal case, supports 15kHz and 31kHz (480p), has a SCART input and RCA outputs for YPbPr component and stereo audio, and comes with a wall wart PSU.

Or, for $50 USD, you can get that transcoder from New Zealand. Although lacks a case, and it's not clear whether it supports greater than 15kHz video, it has the same I/O connectors as the ShinyBow and uses common MicroUSB for power.

What's neat about the proposed module is that it's extremely simple; it doesn't rely on any electrolytic capacitors (which tend to leak after a number of years or when exposed to a lot of heat), it sounds like it could handle everything from 240p to 1080p, and its simplistic design has the potential to fit into a SCART head, which means the potential for premade, inline SCART/DE-15 RGB to YPbPr component converters--no exposed PCBs, no fabrication required by the buyer, recognizable and common USB for power, and it can probably hit a sweet spot between $40 and $60 (depending on things like parts cost, labor, and popularity). (And no, I'm not telling Mike Chi how to price his devices. )

I think most of us are trying to connect RGB-capable game consoles to YPbPr-capable consumer CRTs, not so much arcade boards; so the JROK simply doesn't make sense when products like the SB-2480 or the NZ transcoder are readily available and Mike Chi's is coming in the relatively near future, all at or around the same price and all simply working out of the box with RGB SCART.

Alright here it is... all fitted into a SCART head and still no electrolytic caps!



I'll build a few of these and see if we can get this little guy in the $40 to $60 range

Please tell me this is powered by the SCART connector instead of a USB port.

[nmalinoski]

Please tell me this is powered by the SCART connector instead of a USB port.

It'll have USB power, because the voltage and amperage from SCART sources varies and is unreliable; and, even if pins 8 or 16 had guaranteed 5V, it's meant for signalling, not power delivery.

[samson7point1]

Please tell me this is powered by the SCART connector instead of a USB port.

It'll have USB power, because the voltage and amperage from SCART sources varies and is unreliable; and, even if pins 8 or 16 had guaranteed 5V, it's meant for signalling, not power delivery.

The HD Retrovision cables don't seem to have a problem using it. Any chance of making it selectable?

[nmalinoski]

Please tell me this is powered by the SCART connector instead of a USB port.

It'll have USB power, because the voltage and amperage from SCART sources varies and is unreliable; and, even if pins 8 or 16 had guaranteed 5V, it's meant for signalling, not power delivery.

The HD Retrovision cables don't seem to have a problem using it. Any chance of making it selectable?

The HD Retrovision RGBS->YPbPr cables are built for specific consoles, not to SCART specifications. They pull 5V from a pin on the console's AV port, not from pin 8 on a SCART connector.

This and this suggest that the most we can really expect on pin 8 from a SCART-compliant device is 5mA (probably less); I'm not sure how much current this transcoder requires, but I would expect it exceeds that.

And, even if pin 8 supplied enough current, it's not guaranteed to be 5V; so additional components would be needed to accommodate anywhere between 5V and 12V, and bring that down to 5V. Those components require space, and it doesn't look like there's any room left on that SCART head board.

It would make more sense to do what HDRV does and produce console-specific cables where it's feasible to get regulated 5V with enough amperage from the console, like the SNES or Genesis.