Obtaining TTL-level Composite Sync from Retro Consoles

[HiroWorship]

Hello everyone,

First just wanted to thank everyone on this board for such amazing information throughout the years.
I’m sure I’m not the only one who has referred to the threads here (as well as individual websites managed by the contributors here) when setting up retro gaming setups with RGB and pro equipment.
Many many thanks to legends like Fudoh, viletim, retrorgb, RGB32E, Voultar, and everyone else on the board and it is humbling to be part of the same community.
I hope I can build up my own knowledge to be able to contribute whenever possible as well!

Moving on to the question at hand: I’m working on custom cabling to connect retro consoles to an Imagenics HDX-1010 RGB matrix video switch, which is essentially a Japanese-market equivalent to the Extron Crosspoint matrix switches. This particular model is RGB/YPbPr only (RGBs and RGBHV), but only outputs what it is given - no sync conversion or transcoding performed.
It has 10 inputs and 10 outputs, and the outputs will be connected to pro CRT monitors (a 15 kHz BVM, multiformat PVM, and multiformat Ikegami HTM).

Since this switch expects TTL-level sync (although a toggle for each input can be set to account for 75Ω video-level sync) and only outputs TTL sync, I am looking to keep the cabling as simple as possible since all of the monitors will accept TTL sync.

Here are the specs on the matrix switch (translated directly so any omissions on are the part of the manufacturer):

Video Input:
0.7 V(p-p)　75Ω / 1.0 V(p-p) 75Ω when including sync
Video Output:
0.7 V(p-p)　75Ω / 1.0 V(p-p) 75Ω when including sync
Sync Input:
0.3 V(p-p) ～ 4 V(p-p) TTL switchable, positive or negative polarity
Sync Output:
TTL 75Ω drive, positive or negative polarity

Reading the specs and manual my understanding is it has sync input impedance at 510Ω (switchable to 75Ω using mechanical toggle at the input) and sync output impedance at 75Ω with sync input voltage from 0.3V to 4V nominal (though it will probably take a maximum of 5V) and output voltage of 5V TTL.

I’m only feeding pro monitors that can take TTL sync input voltage, so I’m not concerned with the output from the switch.
Just want to make sure that the TTL sync voltage from the consoles can be fed directly to the switch without additional passive components in the sync lines.

I’m working on cabling using the following resources:
http://www.retrorgb.com/csync.html
http://members.optusnet.com.au/eviltim/ ... escart.htm
http://gamesx.com/wiki/doku.php?id=av:av_pinouts

The RetroRGB page on csync has been extremely helpful in determining what consoles natively output TTL-level sync, and I am basing my assumptions on that, but I can’t find definitive information on the voltage levels of the sync signals coming from these consoles even after a thorough Google search and forum search here.
I know that passive components (470Ω resistor and 220μF capacitor in the case of the Saturn, for instance) are needed to bring impedance and voltage in line with normal video sync levels, but in the case where TTL voltage and high impedance are acceptable, I’m assuming these components are unnecessary?

I’m using Tim’s page for pinouts and circuit diagrams but I know that he himself has mentioned on some threads here that the info may be out of date in some places so I just want to be sure.

I’m beginning cabling efforts with the following 3 consoles that are supposed to provide TTL sync output directly; I’ve included my planned cable configuration below.
Please be so kind as to let me know if any of my assumptions are incorrect.

1. Sega JP Mega Drive 1 non-TMSS model
- 262-degree DIN8 to junction box to 4 BNC
- 75Ω resistor and 220μF capacitor on each RGB line
- CSYNC from sync pin on connector with no passive components for TTL sync
* I’ve read that some models of Mega Drive 1 have this sync pin connected incorrectly? Is there a proven way to test for this?

2. NTSC Super Famicom 1CHIP-02
- Nintendo Multi-Out connector to junction box to 4 BNC
- 220μF capacitor plus 750Ω resistor (to fix 1CHIP signal voltage level) on each RGB line
- CSYNC from sync pin on connector with no passive components for TTL sync

3. Sega Saturn
- 10-pin Mini DIN to junction box to 4 BNC
- no passive components on RGB lines needed
- CSYNC from sync pin on connector with no passive components for TTL sync

Thanks very very much to everyone in advance for chiming in if they see that I have made an incorrect assumption.

I’ll update with pics once everything is set up!

[HiroWorship]

Sorry to self-bump, but if anyone has any opinions on this I would very much appreciate it.
If not, I'll use the passive components indicated for each console just to be safe.

Thank you!

[syboxez]

For the Saturn: You need a series 100uF capacitor on the sync line (220uF should also be fine)

For the Genesis: You need a 220uF capacitor on the sync line

For the SNES: Direct wiring, no components needed

http://www.retrorgb.com/csync Basically that, but without the resistors. Also the Crosspoint does accept 75 Ohm sync as well as TTL sync. It will output TTL regardless though. With my Crosspoint, I feed TTL sync from all of my consoles to it just to have less components in my BNC cables. Not sure if the Imagenics HDX-1010 accepts 75 Ohm sync since I can't read Japanese.

[HiroWorship]

Hi syboxez, thanks so much for the advice!
Completely understood.
So I don't need the resistors to attenuate the signal down to 75 Ohms, but I do need the capacitors to make sure it is buffered.
Perfect!!

The HDX-1010 does take 75 Ohm input (there is a toggle switch next to each input channel) but it's the same as your Crosspoint - it only outputs TTL so no reason not to feed it TTL to cut down on the passive components.

I appreciate the help!
Now to get to work...