Ahhh I didn't notice. Just like audio, which is AC coupled, you need a negative supply for AC coupled video, or DC video with -0.3V sync. It cannot be assumed all video is DC coupled and with a suitable positive offset because often it's not! TVs only terminate the signal to GND, they aren't mid-supply biased because this would break DC coupled video. In the past all consumer video was AC coupled for short-circuit protection and so that a class A amplifier output stage may be used. A +- 3.3V supply will switch nearly all consumer video, just like audio. It will have trouble with DC coupled video with a high offset though, like poorly modded game consoles. +5V, -3.3V should switch everything. If you don't want to add a negative supply then another way is to bias the signal to mid-supply through very large resistors so it doesn't affect DC video, then AC couple it a second time with 75 ohm mid supply termination so that signal levels will still swing the correct level. From there you need a video amplifier with a clamp so that it may recover a suitable DC offset... This should work with all video, but the performance might be bad.
Ok I finally got around to testing which of my systems needs the Sync Strike: N64: No Xbox: Yes SMS: No PS1: No PS2: No NES: No SNES: No Jaguar: No DC: Yes Neo Geo: No Genesis 2/32X: Yes Saturn: Yes So it's Genesis 2, Saturn, Dreamcast, and Xbox. Looks like the Sega consoles need a sync stripper (except for the SMS).
Thanks for testing, this information is very helpful to me! And actually my NTSC SMS also requires sync stripper, so I guess it depends on console revision. I have yet to check my DC.
Thanks for explaining, now I got it! However I don't see any picture degradation on my equipment (XRGB-Mini and THIS) Negative power supply will be added to next PCB design, but I don't know when it will happen . Well, technically I can replace 5V with 3.3V voltage regulator and put 4 wires to each of multiplexers, but in this case I would have to remove LM1881, and from what I see it's needed for few consoles. As of my progress: I am still waiting to get proper Dreamcast and XBOX SCART's, my Dreamcast SCART doesn't have power pin routed at all, and it doesn't ground DC pin7 for RGB mode. Starting next week I think I can sell few fully assembled switches by manufacture price just to see some external feedback.
From SCART pin 8 through low dropout 5V voltage regulator. Sorry for not replying earlier, was busy with real life lately. What is remaining to check is daisy-chaining, will solder 2nd switch this weekend and hopefully I will be able to ship it next week (if you're still interested).
Thanks for the reply, yes still interested. Have you thought about powering the LM1881 externally instead of relying on pin 8? I have read that some systems have trouble providing +5V (PC Engine and Xbox 360, and some instances of PS1 and SNES). Sorry if this has already been covered.
Thanks, I understand. I hope my PC Engine will work properly. For the male-male mini din 8 cable, what are you using? The mini's input socket is a bit deep so I had to modify the mini din 8 connector I had when making a male scart to mini din 8 patch.
I soldered round MiniDIN plug (which doesn't fit to XRGB but fits in switch) to some factory MiniDIN cable assembly with flat top (it fits perfectly to XRGB) - still need to investigate where to get such cables. Plan was to supply MiniDIN -> SCART male with every switch. But I can also do MiniDIN -> MiniDIN cable, just need to get some of these cable assemblies with flat top. Anyway if you are going to use daisy-chaining - you will need MiniDIN -> SCART.
I see, so for 12 consoles I would need two switches, 1 mini DIN male to SCART (male), and 1 mini din male-male.
I finished soldering of 3 switches and SCART cables for it. Everything tested from my side, and these are ready for shipping, I am currently doing final calculations. These 3 will go as cheap as possible because I need external feedback. This means I am not including any component shipping prices I paid, board design labor, soldering labor, etc. This means that buyer pays only for physical components price (well, I even don't include solder ). I will reply here in an hour with picture of what you will get and price.
So each switch will cost $81.04 + shipping . I can PM price breakdown if needed. One switch is reserved for Airs, two are available to buy. You will have one week during which you can return it back, if you have technical reason, and I will refund you full price (minus shipping, and you pay return shipping).
have you had many people come up and ask to buy these ? i would buy one but not being able to have the money for a few weeks would probably see me having no chance at getting one
There is one remaining as of now, but I don't think it will last long. Well, I may solder two more switches for same "promotional" price (3 is too low for feedback, 5 switches should be fine), I will keep one PCB for you, and when you'll let me know you're going to get one - I will solder it (for same $81 price).
I would appreciate that, thank you very much. I'll try my best to get the ££ ASAP Edit, More than likely be at the end of the month
