Thanks for the definitive explanation, when I was toying with the idea of amplifying colour I stumbled across some info detailing that the phase could be wrong. Very nearly ordered a Kramer VM-9YC so I could fiddle around with C-phase, but if I’m going to spend $80 (CAD) on something the Retrovision cables are a much safer bet.
I would have pulled the trigger already if they were in stock. 🙂
Will the HD Retrovision cable require R45 (composite) to be reconnected for sync, or any other reason?
edit: Sorry, I have a bad habit of answering my own questions! Why on earth can’t they use CSYNC on pin 5? Meh…
From HD Retrovision FAQ
Do your cables use CSYNC to avoid the noise from composite video?
The SNES/Genesis YPbPr cables do not use CSYNC. However, through the custom design of our cable and its circuitry inside we are able to extract sync from composite video without introducing noise. The two main reasons for this are (1) we are not driving a full video load, and (2) composite video is only traveling over a short distance before being terminated.
So I need pin 4 on the multi-av out to work at least in some capacity. R45 on the 32X schematic is not directly in the path of pin 4, but completes a little circuit betweeen YOUT and YIN back into the video encoder. Obviously there is already good sync coming out of that pin 6 to R45, so I would suppose the video encoder will want it back to complete the composite signal…unless VOUT already gets sync through the encoder by some other internal routing (doubtful).
I guess I’ll pre-order the cables and find out this summer!
edit 2: Yes, the encoder does require that circuit for a complete composite signal, it goes back in for Y/C mix.
However, do the retrovision cables really require the composite colour information too?
Seems I could just short pin 6 directly to CE12, and disconnect pin 20 by a switch or by simply lifting the pin. I would imagine there is the potential for less interference from the ultimately unused colour signal if it’s not passed on to the HD cable. Or I can reconnect R45 and nerf the colour circuit by getting rid of C76 (easier and better method).
Am I crazy?