Hi All,
Verault on eBay sells these Apple IIc connectors that claim to improve the video output via composite.
I'm wondering if this adapter just takes the pin 12 NTSC video output from the 15-pin connector on the back of the IIc and connects it straight to composite. Or is there some additional logic going on inside the adapter he sells. The item shipped for me is $50; if it turns out to be just a straight though then the cost is a bit high.
Above is from the IIc schematic. "VIDOUT" goes to the composite connector, while "NTSC" goes to connector's pin 12 on the back of the IIc.
This would lead me that the NTSC signal is going straight to the composite connector for the adapter being sold on eBay. (Maybe a resistor or capacitor is added).
If so, I'm also wondering if the NTSC signal output is indeed better quality than VIDOUT as the seller claims, and if so why?
UE1 VID 1 is part labeled 303-1001 on the package, there are no schematics for it.
Anyone know how pin 8 and pin 9 differ on the output, or can any shed any light on this subject? Thanks!
I don't think there are any electronics inside. It's just a straight adapter you can make yourself. This is my opinion after reading this:
https://devonhubner.org/AppleIIc_Video_Port_Breakout/
Thanks CVT! That helps a lot and does seem to confirm it's a straight through.
My remaining questions is if anyone knows what the difference between VIDOUT and NTSC is?
The VIDOUT contains an L-C network which is an impedance matching tool. This is in place to match whatver the source impedance of the driving circuit is (it should be very low with those values) with the expected 75 ohm load at the monitor (taking the cable into account).
This will reduce high frequency noise, improve picture stability and is a preferred method to get video out.
Mind you, I have experimented with this - having built such a cable (with the addition of 12V of power taken from pin 8 of the video port for my Night Owl 9" LCD monitor) and have not seen any difference in picture quality, despite not having used the correct cable (but on the other hand the run is quite short and is a twisted pair so cable noise effects are minimal).
The most difficult thing for an LCD monitor to reproduce is the 80 column screen - quite often they don't sync up perfectly with the incoming signal and the text characters get distorted, most easily seen with a screen filled with the uppercase character "A".
So in my opinion, the claim of "improved picture quality" is hogwash and apart from a cool connector, the eBay seller is peddling snake oil.
You might want to look at my investigation into this. I did this on an Apple //c+ but the circuitry is similar to the //c.
It does how quite clearly that the NTSC direct out has a lot of high frequency noise on the signal along with some undershoot ringing on the trailing edge of the waveform.
The VIDOUT pin should produce a truer picture.
But it's all relative - this reminds me a lot of the analog vs digital arguments int he audio world.
Much of what digital aficionados claim is "superior sound" is actually based on signal artifacts similar to those.
It's one's personal preference. Some may actually like the "sharper" image, but that's not the intention of the signal.
My snake-oil comment stands.
I suspect that whether you can see a difference in the video may depend on the monitor in question. Some may respond better to the VIDOUT vs NTSC, some vice-versa perhaps. But I also suspect that any difference is probably very small most of the time and probably not worth spending a lot of time and money on. But I could be wrong.
The best way to tell if it's better is to just try it. Just cut a coaxial cable, plug the center wire into pin 12 and attach the shield with a screw to one of the nuts of the 15-pin monitor connector. If you like it better, then it's better. Simple.
Like I said, the artifacts can make text more readable which really is the "intention" of the signal. And almost all monitors today have a "sharpness" control which basically does the same thing. Modern HDTV's and digital broadcasting do lots of signal processing to the point where it looks nothing like the old analog NTSC signal. Yet, there's no debate that the pictures do look better than the old analog way.