NightWolve wrote: Rellikami wrote:
Tried using the 2N4401 with the schematic you posted for the S8050, actually got some results that were not black and white though not super impressive. Tested the volts on Y Pr Pb Y was 3.46V from the chip and 1.56V at pin 7, Pr was about 3.52V at the chip but through the amp circuit it was 1.62V Pb was 3.48V from the chip but through the amp is about 1.58V everything looks much better voltage wise now. here is the snes with the transistor amps Pr and Pr from chip into the amp Y from pin 7.
Hey Rellikami, I'm a friend of Retrogamer's over at PCEFX and he showed me this thread some time back. I got started on the SNES mod because of what happened here
and have been working on it ever since on and off depending on mood/interest. I made a current thread here
, though I'll update my posts here about it if there's something of note. Anyhow, that's actually my first amp up there that you used with the S8050 (told Retrogamer about it some time back
) and I was trying to tweak it when I discovered something interesting today: the Blue-Y output doesn't need amplification at all!
I'd like you to try this amp if you got the time or anybody else that has the S-ENC chip
(don't know about the other one):
of course should come direct from the Multi-AV S-Video pin as it's perfect (redundant).
** S-ENC Blue-Y pin
-> (+) 220 uF capacitor (as DC filter) (-) -> 39 Ohm resistor -> RCA Out to TV!
BOOM! 1 cap, 1 resistor. That's it! Very Simple! It turns out that the DC voltage was too strong such that when you'd plug it directly into the TV's 75 Ohm jack and that impedance resistor would ground it, it'd weaken the signal to the point where it'd look like it needed amplification... But if you just use a capacitor as a DC filter and plug that in-between, Blue-Y will wind up being too powerful actually!!
The Red-Y however, that's a different story; that needs maximum amplification and transistors are coming up short. You get the exact same results with the 2n3904, S8050 or the SNES 2SC1815 transistors (I tried all three).
The way I currently have the Red line is:
** S-ENC Red-Y pin
-> diode -> SS8050/2N3904/etc transistor + 5V source -> emitter output goes to 80 Ohm pull down resistor AND to a 220 uF capacitor -> RCA Out to TV!
It's the same as my old photo that's linked, but instead of 1k resistor, use a diode, instead of 470 uF cap, use 220 uF, plus *no* 15 Ohm output resistance! You need the maximum that the transistor can amplify here, at least, that's my finding for my system. If you don't have a diode, you can leave it out. It's for protection and doesn't cause resistance of signal in this scenario if facing in proper outward direction, away from chip. Your final circuit, when ready to build on a PCB could include it if you want anti-static protection for the chip and in case of a transistor short sending +5V back to the chip, etc. Can't use it with the Cap trick for Blue-Y. Signal won't move through in that case.
Note: I am still tweaking both circuits, but lemme know about Blue-Y. If this is the case with other S-ENC chips, then the circuit can be much easier for everyone! To buy a chip if only Red-Y needs amplification may not be worth it if it pans out for most.
P.S. I recently bought a nice toy which has been a big help for tweaking this mod:
http://www.ebay.com/itm/120966019918?ss ... 1439.l2649
It's a F03147 HD USB 2.0 Video Audio Capture Grabber
with YPbPr support! $23 shipped!
I rolled the dice in buying this because you don't know if 240p will be supported, but thankfully, it worked perfectly! So, with this device, you can take digital screenshots on your PC of Composite, S-Video and Component, side by side, page up/down very quickly on them to see how well the color level and tint match up, etc. The included software is kind of cheap, but it works with any DirectShow supporting software like DScaler and any other Movie Capture software, etc.
EDIT: Just made a really easy image for this all.
Extra Notes: It's important to understand that the circuitry of a TV set that processes an analog YPbPr Component video signal varies and even if we could figure out the perfect output circuit, you're still gonna get people complaining about green levels, tint, etc... That's the unfortunate reality.
Examples: I have a Samsung LCD 19" TV that can process a 240p signal thankfully. It computes the color green perfectly. This is testable with Super Street Fighter II, the Ken stage where the water is supposed to be green and also with Super Mario World, the title screen. However, my old school Panasonic 32" CRT TV has a problem computing green from a Component signal and it's usually darker and/of the wrong tint, looks more bluish. It just doesn't compare to the brightness/tint of when you switch to Composite/S-Video. So on the same set, the circuitry for Composite/S-Video, properly displays green color as it should be. Two different sets+capture device, same circuit on console, yet green is wrong in one, the CRT.
The other issue is how it handles red, apparently. My Component-to-USB device tells me that I need a little more amplification for red, so it's almost perfect with no output resistance, just straight from the transistor with filter cap seems right. This also holds true for my Samsung LCD. But again, this old school CRT tells me that the red is a little hot and could use a 15-25 Ohm output resistor which is why my first circuit that Retrogamer posted has 15 Ohm resistors on the outputs... So anyhow, I am preferring to trust my USB device here in the view that a circuit revolving around that would produce the most universal result, while accepting that some TV sets you're gonna have differences and people may customize the circuit to fit that particular TV set.
Pasky wrote:I also noticed the Luma from the Multi AVOUT was also a bit too strong for component. I added a 15Ohm resistor to it as well but still feel it's a bit too bright but I can live with it.
Well, the Luma out of SNES units for S-Video is perfect. Both S-Video and YPbPr are referred to as Luma-Based Component video signals, so in principle the Luma from the Multi-AV out should be left alone for general mod guides. The reason you're seeing a difference is because of what I mentioned above, the circuitry of TV sets vary and even on the same set, S-Video and YPbPr processing vary. S-Video mode on my TV has options and filters that are off or don't apply when switched to YPbPr mode, etc. That's what explains all that, so just FYI in general. Point is, they are the same Lumas, just that YPbPr splits Chroma into Red-Y and Blue-Y rather than transmit them together as S-Video does. Anyhow, my 2 TVs (New LCD and old CRT) and my USB device with my SNES unit show that Luma is rocksolid when connected via the YPbPr jack.