YPbPr ouput mod for SNES consoles

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Ziggy587
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Location: NY, USA

Re: YPbPr ouput mod for SNES consoles

Post by Ziggy587 » Thu Feb 07, 2013 6:23 pm

So I have some results. I don't think it's yet perfect, but we're closer now than before.

I tried a bunch of different things, so I'll try to be thorough in my explanation to avoid confusion. So sorry if this turns into a wall of text, especially because of my lack of knowledge on the matter.

First, I wanted to experiment with the voltage coming off the Pr and Pb lines. I am again using the Pr and Pb output pins (pins 1 and 24). I made a table so it'll be easy to understand. I noticed that the voltage varies, so I just loaded and game and paused it, so the voltage would remain the same through all my tests.

Image

The X column means no components for Pr and Pb, just the voltage coming straight from the encoder's pins. In Y's case, X means the voltage measured at the output. The RC column means Pr and Pb pass through this circuit. RC+1k is the same circuit but with a 1k resistor to ground at the end of it. 100µF and 220µF are the capacitors I tried using in place of the RC circuit. In both cases, I had the positive leg going toward the encoder and the negative leg going toward the TV.

Some one said that the RC circuit would be better to use than a single capacitor in the case of voltage spikes. I have no idea if that's true or not. For the rest of my testing, I used the "RC" circuit (with out the extra 1k resistor to ground at the end).

Next, I tried the THS7314 amp. This is how I wired it, as per the datasheet:

Image

Note A in the datasheet says, "Due to the high frequency content of the video signal, it is recommended, but not required, to add a 0.1-μF or 0.01-μF capacitor in parallel with these large capators." Oh wow, they misspelled capacitors LOL. So, I added .1μF caps in parallel with the 330μF caps. The results of this were... not good. Everything was wrong looking, like a bad acid trip. I tried playing with it, first by removing the .1μF caps. Then I played with every combination of removing the output caps and resistors. I even tried it with no caps or resistors, which made Pr and Pb MUCH too bright. So, I don't know if I made a mistake some where. Instead of looking it over, I decided to try the next amp.

Next I tried the NJM2267 amp. I built it exactly how it is here. I tried it with and without the series 75ohm resistor. Pr and Pb are definitely too bright without it. It was looking pretty good, so I decided to take a few screen shots real quick. I wanted to be able to compare it to something close to equivalent. So, I used bSNES (latest version) as one. As the other, I used one of my SNES that's the 1chip revision. This SNES is outputting RGB into a professional grade transcoder (no upscalling or anything) then component into my TV. The TV is a 1080p LCD. I took the pictures with a DSLR. I didn't take the time to use a stand and focus perfectly so the pictures aren't super. However, it's a test of color levels, and not of sharpness or anything else.

bSNES:
Image

1chip:
Image

S-ENC:
Image

What's funny is that usually the 1chip SNES is more desirable because of the sharper image (see here). But on a 1080p HDTV, perhaps the slightly blurry picture from the older SNES is more desirable. Because the 240 resolution is being blown up to 1080, perhaps the slight blur actually helps. I should have taken a picture of composite on this TV because it actually looks quite good. Bah, I don't wanna get off topic.

For this next set of pics, the S-ENC pic is a little messed up. For some reason the water looks really weird. But if you look in the upper right corner, you can see how the path is obscured into the grass. That is close to how it looks on my TV, though not quite as bad. I think that shot was overexposed or something. But even still, the colors are fairly accurate.

bSNES:
Image

1chip:
Image

S-ENC
Image

So I'd have to say it's a LOT closer to where it should be. It's almost perfect now.

AaronE
Posts: 28
Joined: Mon Jan 21, 2013 7:25 pm

Re: YPbPr ouput mod for SNES consoles

Post by AaronE » Thu Feb 07, 2013 7:34 pm

Can you give me a schematic of what you built using the NJM amp?

Ziggy587
Posts: 117
Joined: Fri Oct 08, 2010 6:08 pm
Location: NY, USA

Re: YPbPr ouput mod for SNES consoles

Post by Ziggy587 » Thu Feb 07, 2013 8:52 pm

Currently, I have it exactly like this:

Image

+

Image

Only without the second NJM amp, of course.

edit: I think we might be able to remove some components though. Maybe replace the first RC circuit with just one capacitor, or maybe remove the resistor and/or capacitor from the NJM amp input. I just don't know enough about this kind of stuff, I'd have to rely on trial and error unless some one can give some input.

Retrogamer
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Joined: Fri Feb 22, 2013 7:15 am

Re: YPbPr ouput mod for SNES consoles

Post by Retrogamer » Fri Feb 22, 2013 9:59 am

Why are you grabbing the Luma (green) from the chip? You can use the luma from the Multi AVOUT port which already gives a perfect luma and just run that straight to the RCA jack.

Ziggy587
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Location: NY, USA

Re: YPbPr ouput mod for SNES consoles

Post by Ziggy587 » Sat Feb 23, 2013 5:55 am

Retrogamer wrote:Why are you grabbing the Luma (green) from the chip? You can use the luma from the Multi AVOUT port which already gives a perfect luma and just run that straight to the RCA jack.
We are.

Retrogamer
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Re: YPbPr ouput mod for SNES consoles

Post by Retrogamer » Sat Feb 23, 2013 9:21 am

Ziggy587 wrote:
Retrogamer wrote:Why are you grabbing the Luma (green) from the chip? You can use the luma from the Multi AVOUT port which already gives a perfect luma and just run that straight to the RCA jack.
We are.
Ah, I was going by your schematic that had a green input as well...

Ziggy587
Posts: 117
Joined: Fri Oct 08, 2010 6:08 pm
Location: NY, USA

Re: YPbPr ouput mod for SNES consoles

Post by Ziggy587 » Sat Feb 23, 2013 3:34 pm

Yeah, I know it's a pain in the ass, but you'd have to read from the start. That schematic is the one posted on GameSX for an N64 RGB mod, that's why there's red, green and blue. I'm only using it for Pr and Pb.

Retrogamer
Posts: 9
Joined: Fri Feb 22, 2013 7:15 am

Re: YPbPr ouput mod for SNES consoles

Post by Retrogamer » Tue Feb 26, 2013 9:39 am

Ziggy587 wrote:Currently, I have it exactly like this:

Image

+

Image

Only without the second NJM amp, of course.

edit: I think we might be able to remove some components though. Maybe replace the first RC circuit with just one capacitor, or maybe remove the resistor and/or capacitor from the NJM amp input. I just don't know enough about this kind of stuff, I'd have to rely on trial and error unless some one can give some input.
So in this schematic, are you doing for instance:

pin 24 -> 270Ohm (+ grnd) -> 220pF -> 1 uF -> 10uF -> Amp in?

I'm confused because you put a schematic and then a + for the other schematic and not sure what you mixed. The reason I ask is I would like to try this amplifier out because I'm currently running the blue and red's through a transistor and the colors aren't quite right and are kind of weak. Any help would be appreciated or an actual schematic of what you have exactly would be great. Thanks.

SheepyGuy
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Joined: Wed Feb 27, 2013 6:06 am

Re: YPbPr ouput mod for SNES consoles

Post by SheepyGuy » Wed Feb 27, 2013 6:12 am

I'm running my Pb and Pr through a 100μF capacitor (and nothing else) before hitting the RCA jacks and that's helped the color saturation a lot. I don't think it's perfect, maybe off by just a bit, but close enough that I'm pleased.

Ziggy587
Posts: 117
Joined: Fri Oct 08, 2010 6:08 pm
Location: NY, USA

Re: YPbPr ouput mod for SNES consoles

Post by Ziggy587 » Wed Feb 27, 2013 2:07 pm

Retrogamer wrote:So in this schematic, are you doing for instance:

pin 24 -> 270Ohm (+ grnd) -> 220pF -> 1 uF -> 10uF -> Amp in?

I'm confused because you put a schematic and then a + for the other schematic and not sure what you mixed. The reason I ask is I would like to try this amplifier out because I'm currently running the blue and red's through a transistor and the colors aren't quite right and are kind of weak. Any help would be appreciated or an actual schematic of what you have exactly would be great. Thanks.
I was planning on making a proper schematic after everything was finalized. But here, I did a quick cut and paste job so you can see what I did without confusion...

Image

In this above picture, that is how I currently have it wired. It might be possible to replace the first part of the circuit (what we're calling the "RC circuit") with a single 100 or 220 uF capacitor. So, it'd be like this:

Image

I've tried it that way too, with no discernible difference in the video quality.

I've explained pretty much everything I've done in this post: viewtopic.php?p=107496#p107496

You might wanna read this thread from the start though, if you feel out of the loop about anything else.

If you try this amp, be sure to let us know your results! In my opinion, the reds are a tad high, but it's otherwise perfect. Let me know if you have any more questions.

Retrogamer
Posts: 9
Joined: Fri Feb 22, 2013 7:15 am

Re: YPbPr ouput mod for SNES consoles

Post by Retrogamer » Wed Feb 27, 2013 3:12 pm

Thanks! Will do, I'm ordering the parts as we speak. You could try adding a 10Ohm to the red output before it gets to the rca jack to lower the red's strength.

Rellikami
Posts: 3
Joined: Sat Mar 02, 2013 11:48 am

Re: YPbPr ouput mod for SNES consoles

Post by Rellikami » Sat Mar 02, 2013 12:12 pm

Ziggy587 wrote:
Retrogamer wrote:So in this schematic, are you doing for instance:

pin 24 -> 270Ohm (+ grnd) -> 220pF -> 1 uF -> 10uF -> Amp in?

I'm confused because you put a schematic and then a + for the other schematic and not sure what you mixed. The reason I ask is I would like to try this amplifier out because I'm currently running the blue and red's through a transistor and the colors aren't quite right and are kind of weak. Any help would be appreciated or an actual schematic of what you have exactly would be great. Thanks.
I was planning on making a proper schematic after everything was finalized. But here, I did a quick cut and paste job so you can see what I did without confusion...

Image

In this above picture, that is how I currently have it wired. It might be possible to replace the first part of the circuit (what we're calling the "RC circuit") with a single 100 or 220 uF capacitor. So, it'd be like this:

Image

I've tried it that way too, with no discernible difference in the video quality.

I've explained pretty much everything I've done in this post: viewtopic.php?p=107496#p107496

You might wanna read this thread from the start though, if you feel out of the loop about anything else.

If you try this amp, be sure to let us know your results! In my opinion, the reds are a tad high, but it's otherwise perfect. Let me know if you have any more questions.
I was planning on doing this mod on a BA6594af Encoder all 3 snes's i have have the same one.
What i was wodering could you use an NPN transistor such as a 2N4401 in place of an the op amp, similar to the way it is done on the NESp, a single transistor each, one on Pr and and one on Pb taking Y from Luma?
http://nesp.tighelory.com/images/nesp_amplifier.gif
I was planning on going to crappyshack to get some of those today and give it a go on one of them and order the amp you used to do an comparison.
I have both systems wired up the same curently pretty much at this time with the component lines straght off the pins on the BA6594af connected to my sony bravia 32" kdl-32l504.
one is perfect with the color almost at max on my tv, while the other is still very fadded even with the color atr max, this seems odd to me, but i think it has more to do with the diffent motherboard revisions than the encoder chips, i plan on checking the voltage on the lines when i go to put the transistors in.
EDIT: i also have some 4558 dual op amps laying arould in my harvest bin, if someone could help me with a schematic on wiring it up to the Pr and Pb i could test it out.

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mikejmoffitt
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Re: YPbPr ouput mod for SNES consoles

Post by mikejmoffitt » Sat Mar 02, 2013 3:53 pm

I can confirm that different motherboards will produce different levels of saturation on the same set. Also, the two color lines are not always balanced either. There is a lot of variance.

Rellikami
Posts: 3
Joined: Sat Mar 02, 2013 11:48 am

Re: YPbPr ouput mod for SNES consoles

Post by Rellikami » Sat Mar 02, 2013 5:45 pm

So I just tried to use the 2n4401 the results are quite abysmal to say the list, There is almost no color at ALL only a barely visible hint of red.
The only thing i added was a 220uf Cap on the video in everything else was the same resistors used in the NESp which is probably the problem.
Gonna do some test with different variations of lower resistance resistors.

Retrogamer
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Joined: Fri Feb 22, 2013 7:15 am

Re: YPbPr ouput mod for SNES consoles

Post by Retrogamer » Sat Mar 02, 2013 8:22 pm

So my parts arrived today and I rebuilt the amp.

Warning incoming pics...

Here's the old amp I used:

Image

It worked out great but my some of my colors were real weak, heres capture from my startech capture device that can capture 240p component using the old amp:

Image

Image

Image

Now using the new amp ziggy posted (I got rid of the circuit and just used a 220uF between the encoder and the amp):

Image

Notice the leaf's are much greener

Image

The yellow is a bit lighter, but I think this is more accurate.

Image

The ground says it all.

Now some emulator comparisons, I used photo shop to double the size, the colors are what's important though, not the image (BSNES v088):

Image

Image

Image

Overall I'm very pleased. The picture looks even better on my TV than my capture. I'm happy using this amp over the first one I tried. Excellent picture and the colors are great.

For those wondering the capture card used, it's this one:

http://www.amazon.com/gp/product/B007U5 ... UTF8&psc=1

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