*Update2* SPDIF Audio mod Sega Saturn with *ahem* big pics

[SGGG2]

by size I meant millimeters...

[Konsolkongen]

Ah of course. Sorry but the one I used was one I pulled from an old MegaDrive 1 I did some modifications to. Didn't buy it :/
I just installed it in the cable, there's plenty of room in the Scart socket.

[Konsolkongen]

As promised I have tried to draw up instructions to do this mod on a VA13 Saturn. It might partially match other Model 2's as well, but the DAC might be different, and therefore the Reset line goes somewhere else.


2X zoom, click here: http://i40.photobucket.com/albums/e236/ ... inkmod.png

I'll try to explain it as simple as possible. You'll need a CS8406 IC and a Toslink transmitter (see the gamesx wiki for info on coaxial-output).

Fig. 1: Cut a stripboard to 7x7 holes
Fig. 2: Break the traces as shown. Use a power drill for large areas, and a sharp blade to split the traces. Make sure there is NO connection, so use a continuity tester when finished.
Fig. 3: Solder the CS8406 to the stripboard. Be sure that the chip is facing the right way (the dot indicates leg 1).
Fig. 4: All red areas must be connected to 5V and all blue to GND. There are plenty of 5V and GND points located on the motherboard (MB).
Fig. 5: Glue the board unto the MB and solder wires as shown. The Reset wire is the most tricky one, as the leg on the PCM1717E DAC is tiny, so I would highly recommend using kynar and liquid flux here. The C62 and TP-points are located on the underside of the MB. The signal wire connects to the left pin of the Toslink transmitter, looking at the front. Center is 5V and right is GND, I connected these to the red and blue areas on the stripboard.

Here are pictures of the stripboard and MB soldering points:
Stripboard: http://i40.photobucket.com/albums/e236/ ... C00111.jpg
DAC: http://i40.photobucket.com/albums/e236/ ... C00112.jpg
C62 and TP-points: http://i40.photobucket.com/albums/e236/ ... C00108.jpg

I hope this will be useful, even those with different models might be able to work from this. Be sure though, to read the schematics for the DAC if yours is different, to find the proper Reset line-leg. There are also DAC's which requires their EMPH signal to be inverted for Pre-emphasis to work. This wasn't necessary on this model, so I'm probably not the one to ask, brendanraymond on the other hand seems to have a good understanding of this.

Any feedback on this would be highly appreciated

[SGGG2]

Ugh, so I'm using a SOIC to DIP adaptor board and I'm getting some strange continuity connections that don't make any sense...

I wish someone would make a PCB so we wouldn't have to mess with breadboards and whatnot.

[Konsolkongen]

Could you post some pictures please? I only used a breadboard because I was too cheap to buy an adaptor

[SGGG2]

http://i.imgur.com/WLYOQ.jpg
http://i.imgur.com/MZE3c.jpg

I guess I tinned the adapter with too much solder and some of the connections got bridged when I soldered the chip down... That's what I get for being cheap and using a regular size soldering iron.

Somebody design a PCB and I'll seriously consider doing a small production run (of PCB's, NOT fully assembled boards) around 100, more if there's demand.

http://www.gamesx.com/wiki/doku.php?id=av:saturn_sp_dif
http://www.gamesx.com/wiki/doku.php?id=av:dreamcastda
http://www.gamesx.com/wiki/doku.php?id=av:snes_sp_dif

They all use the Cirrus CS8406 chip, so as long as all the required traces are taken into consideration it's interchangeable with all three systems. You'll need a spot for an optional Hex inverter as some DAC's require their EMPH signal to be inverted for Pre-emphasis to work (as Konsolkongen has pointed out.)

[Konsolkongen]

What's with the twisted wires? You did solder these on properly and cut off the remaining wire, right?

As for your CS8406 soldering to the adapter it looks fine to me Try measuring the pins with a continuity tester to check for shorts.

[SGGG2]

I couldn't figure out how to bridge the pins just using solder (it kept evaporating) so I just twisted the wires together.

I get a weak, but definite, continuity reading between Pin 26 (it's empty!!!) and all the pins connected to ground. The bridge must be under the chip, towards the back. It was the first time I've attempted something like this, the iron was too big for the job and some of the contacts got tinned too much.

[Konsolkongen]

Cut of the legs of a resistor or similar component and use that to bridge the points

I'm sorry to hear it may have bridged underneath the chip. It will be difficult to remove it without breaking it. Unless you have the right tools of course

You Saturn is working alright, still? That's all that really matters

[cyborc]

I'm still a bit confused about the whole hex inverter thing....is inverting the emph line absolutely required? as in, will there be no sound if I don't invert the emph line? I was hoping to avoid having to use a hex inverter chip if possible...