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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Thu Oct 04, 2018 9:53 pm 


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Posts: 270
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


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Thu Oct 04, 2018 10:18 pm 



Joined: 01 Jul 2017
Posts: 26
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Thu Oct 04, 2018 10:27 pm 



Joined: 27 Sep 2018
Posts: 41
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?


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Thu Oct 04, 2018 11:41 pm 



Joined: 03 Jun 2018
Posts: 34
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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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 05, 2018 12:10 am 


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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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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 05, 2018 12:10 am 


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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


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 05, 2018 4:13 am 



Joined: 19 Jul 2017
Posts: 657
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 05, 2018 2:54 pm 



Joined: 03 Jun 2018
Posts: 34
Which is why the new gscartsw is so appealing. I can't wait to get mine.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Mon Oct 08, 2018 3:18 pm 



Joined: 05 Dec 2012
Posts: 410
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Mon Oct 08, 2018 4:05 pm 



Joined: 19 Jul 2017
Posts: 657
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Mon Oct 08, 2018 6:29 pm 



Joined: 01 Jul 2017
Posts: 26
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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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Mon Oct 08, 2018 11:45 pm 


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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?


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Tue Oct 09, 2018 12:30 am 



Joined: 01 Jul 2017
Posts: 26
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Wed Oct 10, 2018 12:07 am 



Joined: 08 Mar 2017
Posts: 471
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Wed Oct 10, 2018 12:10 am 



Joined: 01 Jul 2017
Posts: 26
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Wed Oct 10, 2018 12:16 am 



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Posts: 471
Quote:
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?


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 12, 2018 5:10 pm 



Joined: 27 Sep 2018
Posts: 41
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.


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 Post subject: Re: Universal SNES Output Amplifier
PostPosted: Fri Oct 12, 2018 9:45 pm 



Joined: 01 Jul 2017
Posts: 26
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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