Universal SNES Output Amplifier

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maxtherabbit
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Re: Universal SNES Output Amplifier

Post by maxtherabbit »

energizerfellow‌ wrote:
mikechi2 wrote:Thanks for explaining... I actually had a similar discussion with Rob. The regular PS1 cables with the coupling caps *should* work fine on a PS2. But I think what you'd guys really need is a sync stripper for the PS2 @ 480p and above?
With properly shielded sync-on-luma cables and modern displays/scalers I think most of the issues are solved outside of the PS1's coupling capacitors, no sync strippers needed.
sync on luma doesn't work at 480p and up, the PS2 turns off the luma pin
mikechi2
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Re: Universal SNES Output Amplifier

Post by mikechi2 »

maxtherabbit wrote:
energizerfellow‌ wrote:
mikechi2 wrote:Thanks for explaining... I actually had a similar discussion with Rob. The regular PS1 cables with the coupling caps *should* work fine on a PS2. But I think what you'd guys really need is a sync stripper for the PS2 @ 480p and above?
With properly shielded sync-on-luma cables and modern displays/scalers I think most of the issues are solved outside of the PS1's coupling capacitors, no sync strippers needed.
sync on luma doesn't work at 480p and up, the PS2 turns off the luma pin

Gotcha, so it sounds like from all the discussions what is really needed is a circuit that strips the sync from green as necessary as well as select the correct sync source (stripped green, or CVBS) as appropriate.
energizerfellow‌
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Re: Universal SNES Output Amplifier

Post by energizerfellow‌ »

maxtherabbit wrote: sync on luma doesn't work at 480p and up, the PS2 turns off the luma pin
Pretty sure the chroma, luma, and CVBS are all cut at once for anything >15khz or in YPbPr mode on the PS2/PS3? But how big is the sync control need, really, when both the gscartsw and OSSC now support SoG/YPbPr and the PVM guys can just hit the sync source button?
Dazdigo
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Re: Universal SNES Output Amplifier

Post by Dazdigo »

Retro Access was able to solve the PS1/PS2 cable differences by just using higher farad capacitors in the cable. Since I have both consoles, decided to just get one of each since I wanted the lightgun version from Retro Gaming Cables and not deal with the pigtail on Retro Access version of the cable (that I can see myself accidentally tearing off with how I have my console tower currently configured).

Also when Sync on Luma is available, it is always better to go with that over Sync on Composite. There will be less noise issues since less traffic is being sent through the same cable. I can see Mike using SoC here due to the wiring differences between NTSC and PAL (and how the PAL version doesn't have S-Video out).
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maxtherabbit
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Re: Universal SNES Output Amplifier

Post by maxtherabbit »

Dazdigo wrote:Also when Sync on Luma is available, it is always better to go with that over Sync on Composite. There will be less noise issues since less traffic is being sent through the same cable. I can see Mike using SoC here due to the wiring differences between NTSC and PAL (and how the PAL version doesn't have S-Video out).
since he's stripping the sync on a board located at the multiout, there's no argument against CVBS-as-sync - there's no cable for it to travel through to cause coupling related issues
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maxtherabbit
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Re: Universal SNES Output Amplifier

Post by maxtherabbit »

energizerfellow‌ wrote:
maxtherabbit wrote: sync on luma doesn't work at 480p and up, the PS2 turns off the luma pin
Pretty sure the chroma, luma, and CVBS are all cut at once for anything >15khz or in YPbPr mode on the PS2/PS3? But how big is the sync control need, really, when both the gscartsw and OSSC now support SoG/YPbPr and the PVM guys can just hit the sync source button?
true, and a good point
nmalinoski
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Re: Universal SNES Output Amplifier

Post by nmalinoski »

energizerfellow‌ wrote:
maxtherabbit wrote: sync on luma doesn't work at 480p and up, the PS2 turns off the luma pin
Pretty sure the chroma, luma, and CVBS are all cut at once for anything >15khz or in YPbPr mode on the PS2/PS3? But how big is the sync control need, really, when both the gscartsw and OSSC now support SoG/YPbPr and the PVM guys can just hit the sync source button?
Luma, chroma, and CVBS are cut for >15kHz when in RGB mode. I imagine chroma and CVBS get cut in YPbPr as well, but not luma, because luma is Y and integral to YPbPr. :)

The main reasons for automatic RGsB->RGBS conversion are so that you don't have to toggle input mode on the OSSC, and to enable the PS2 to continue to operate with SCART equipment when switching to 480p and better video modes.
Dazdigo
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Re: Universal SNES Output Amplifier

Post by Dazdigo »

Which is why the new gscartsw is so appealing. I can't wait to get mine.
RGB0b
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Re: Universal SNES Output Amplifier

Post by RGB0b »

mikechi2 wrote:The regular PS1 cables with the coupling caps *should* work fine on a PS2. But I think what you'd guys really need is a sync stripper for the PS2 @ 480p and above?
Ste did some research on this and found that as long as a much higher rating cap was used, it would be fine in both consoles. I think it was 1000uF instead of 220uF, but I can't remember.
nmalinoski
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Re: Universal SNES Output Amplifier

Post by nmalinoski »

retrorgb wrote:
mikechi2 wrote:The regular PS1 cables with the coupling caps *should* work fine on a PS2. But I think what you'd guys really need is a sync stripper for the PS2 @ 480p and above?
Ste did some research on this and found that as long as a much higher rating cap was used, it would be fine in both consoles. I think it was 1000uF instead of 220uF, but I can't remember.
The Retro-Access PS1/2/3 cables were indeed advertised to use 1000uF/1mF caps.
mikechi2
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Re: Universal SNES Output Amplifier

Post by mikechi2 »

nmalinoski wrote:
retrorgb wrote:
mikechi2 wrote:The regular PS1 cables with the coupling caps *should* work fine on a PS2. But I think what you'd guys really need is a sync stripper for the PS2 @ 480p and above?
Ste did some research on this and found that as long as a much higher rating cap was used, it would be fine in both consoles. I think it was 1000uF instead of 220uF, but I can't remember.
The Retro-Access PS1/2/3 cables were indeed advertised to use 1000uF/1mF caps.
It hurts me to hear that 1mF caps are being used. :cry:
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maxtherabbit
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Re: Universal SNES Output Amplifier

Post by maxtherabbit »

mikechi2 wrote:
nmalinoski wrote: The Retro-Access PS1/2/3 cables were indeed advertised to use 1000uF/1mF caps.
It hurts me to hear that 1mF caps are being used. :cry:
Why?
mikechi2
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Re: Universal SNES Output Amplifier

Post by mikechi2 »

maxtherabbit wrote:
mikechi2 wrote:
nmalinoski wrote: The Retro-Access PS1/2/3 cables were indeed advertised to use 1000uF/1mF caps.
It hurts me to hear that 1mF caps are being used. :cry:
Why?
They're big, ugly and prone to leakage (electrically and physically). To me, they should never be used as part of a signal path, and only as a last resort for power supply decoupling. Ceramic MLCCs are usually sufficient for low voltage applications and there are ways to compensate for a smaller coupling capacitor using slightly more complex circuitry.
rama
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Re: Universal SNES Output Amplifier

Post by rama »

The 1000uF fix is a workaround that's acceptable at best, as the effective total capacity when used with a PS2 will be less than 220uF.
The problem of course is that you want a multi cable, but one source has coupling caps and the other doesn't.
I don't think there's a better way than the 1000uF workaround.
mikechi2
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Re: Universal SNES Output Amplifier

Post by mikechi2 »

rama wrote:The 1000uF fix is a workaround that's acceptable at best, as the effective total capacity when used with a PS2 will be less than 220uF.
The problem of course is that you want a multi cable, but one source has coupling caps and the other doesn't.
I don't think there's a better way than the 1000uF workaround.
SAG correction or AC-coupling to a high input impedance stage, clamping to ground and then driving with a DC amp is the cleanest way to do it and gets rid of the caps.
rama
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Re: Universal SNES Output Amplifier

Post by rama »

SAG correction or AC-coupling to a high input impedance stage, clamping to ground and then driving with a DC amp is the cleanest way to do it and gets rid of the caps.
Interesting, if it doesn't add too much noise.
I don't know how much the inherent noise of active devices affects these rather low bandwidth signals.
Can you do it noise free? :)

Edit:
And the signals will be DC coupled then? Is this safe?
energizerfellow‌
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Re: Universal SNES Output Amplifier

Post by energizerfellow‌ »

I'm guessing this amplifier circuit could be considered universal for everything modern enough to have RGBs, but too old for YPbPr, excluding the Dreamcast/Gamecube, considering most everything uses some combination of cap+resistor? If so, the HD Retrovision guys might be onto something with a transcoder box that's basically a bump in the wire with replaceable console-specific ends.

Speaking of ends, wouldn't a shielded RJ45/RJ50 connector for the console-specific input cable be both mechanically and electrically better than the mini-DIN? Would probably need to use a connector meant for the larger diameter of CAT 6/7/8.
mikechi2
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Re: Universal SNES Output Amplifier

Post by mikechi2 »

energizerfellow‌ wrote:I'm guessing this amplifier circuit could be considered universal for everything modern enough to have RGBs, but too old for YPbPr, excluding the Dreamcast/Gamecube, considering most everything uses some combination of cap+resistor? If so, the HD Retrovision guys might be onto something with a transcoder box that's basically a bump in the wire with replaceable console-specific ends.

Speaking of ends, wouldn't a shielded RJ45/RJ50 connector for the console-specific input cable be both mechanically and electrically better than the mini-DIN? Would probably need to use a connector meant for the larger diameter of CAT 6/7/8.
Yes indeed - although for generic usage, you could drop the current biasing circuit. That's only needed for the PAL SNES.
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

Hello, I've managed to get in the list of beta testers for RetroGamingCables Universal SNES cable, but I have a few questions. I plan on testing it with my RGB modded AV Famicom and TW RGB modded N64. Now the N64 should need a cable with 220uf caps, just like an NTSC SNES cable, so I expect everything to be fine there. However, the AV Famicom has caps in already. I plan on doing tests and some captures with the caps, and then removing them and doing more tests and captures so I can compare. But just so I know what I should look for, anyone have any idea how the circuitry in this cable will work with an RGB signal that is already attenuated properly? Should I look for the same greyish black levels you get with using two 220uf capacitors in series? Or will that not happen with this cable?

Thanks in advance :D
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

Well no one answered my question :P So I tested the universal SNES cable on my AV Famicom with two other cables; a cheap ebay cable and a RGC NTSC SNES csync Cable as a control test. I tested before and after removing capacitors from the NESRGB board. I was quite surprised to see that it's very dark with capacitors. Thankfully, it's fine once the capacitors have been removed. It seems this cable might not be a good option for NESRGB, unless they KNOW that the RGB capacitors have been removed.
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Digital Dragon
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Re: Universal SNES Output Amplifier

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So after another day of testing I have some results to post. Firstly, with the N64 it unfortunately has a dark image similar to the NES, but not as bad. I was expecting it to work, seeing as the N64RGB board needs a cable with capacitors just like an NTSC SNES. A little disappointing.

Then I tested it with my PAL Gamecube. I expected this to work as well, or at least display some kind of image. But the OSSC read 'No Signal'. I plugged it into my CRT and it showed a band of screen stuff rapidly rolling down the screen. Hey, Mike Chi, did you ever get to test a PAL Gamecube with this? Did you or anyone get something similar? On the plus side it wasn't too dark this time :lol: This could be due to an issue with the Gamecubes sync. I plan on asking Rob from RGC when he gets back to me, his GC cables have a 75ohm resistor between sync and ground to stop some kind of sync issue, if he thinks it's worth it I'll break open the cable and put a resistor between sync and ground before the sync stripper. I looked online but couldn't find anything, is it an LM1881 used in this?

Here's a comparison of the N64 cables and the Gamecube logo intro rolling around my screen;
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rama
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Re: Universal SNES Output Amplifier

Post by rama »

Again the PAL Gamecube!
I hear about sync issues with this console a lot. Is there anything weird going on?
I mean, except the Nintendo typical need to put a 75 Ohm to ground resistor in the console end plug? :p
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

rama wrote:Again the PAL Gamecube!
I hear about sync issues with this console a lot. Is there anything weird going on?
I mean, except the Nintendo typical need to put a 75 Ohm to ground resistor in the console end plug? :p
I have no idea what's happened with this cable and the Gamecube. My guess is, as this cables thing is how it handles the RGB lines, it's handling of the sync line shouldn't be effected by the special circuitry. If the image was too dark or had bad black levels, then that'd be a sign it's the RGB line attenuation. But given that the issue is that the OSSC reads 'No Sync', then it must be to do with the sync line. This doesn't happen with the other cable I use, which is a generic ebay cable with sync on composite, 220uf caps on RGB lines, and no special resistor for sync.
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

RGC sent an email out to all beta testers mentioning that this beta test cable is not compatible with Gamecube. So that explains the issue I had with Gamecube, however the other consoles results still stand.
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

So RGC has gotten back to us beta testers, it seems most of the issues uncovered in the beta test have been fixed with a new version of the PCB. I'm sure he'll explain and show us what this new version is like before releasing it. I decided the only console I could use this test cable with from now on would be my Gamecube, as all my other consoles already have cables. RGC reccomended that if I tried putting a 75ohn resistor between sync and ground before the LM1881 then it should work. By doing this, I now get sync, but it's allowed me to see how this test cable works with the Gamecube. Unfortunately like some of the other consoles the image is too dark. This will not affect the cables that will eventually go up for sale, just beta test cables like mine.
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rama
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Re: Universal SNES Output Amplifier

Post by rama »

Hm, what's going on there?
What's in the Gamecube that makes it apparently so hard to get an RGB cable circuit correct?
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Digital Dragon
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Re: Universal SNES Output Amplifier

Post by Digital Dragon »

Apparently it was a DC biasing issue that caused the dark image with all the consoles. No need to worry as the cable shouldn't have this problem when it's released. What I posted is just for beta testers like me who want to use their beta cable with the Gamecube.

One interesting thing I've noticed though is that both cables have a purplish tint. I hope it's not my Gamecube breaking or something.

Edit: Found out why I had Purple-o-vision, the scart cable connecting my switcher to the ossc seems to be broken. Good to know it's my Gamecube.
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