SNES/PDIF Digital Audio Mod

Compatibility

This mod kit is electrically compatible with all models of the SNES, including JP and PAL regions.  However, I have customized the PCBs to make them easier to install in specific models.  Getting the correct version to match your console's hardware revision will greatly improve the ease of installation, as well as the quality of the final result.  Here is a table showing which mod versions are designed for which console revision.

Revision Identification

In order to determine exactly which version of the kit is compatible with your system, you need to identify the exact revision of the console.  This kit is region-agnostic, so the identification of model for the purposes of compatibility is the same across all regions.  The easiest way to determine your model is to open the console and look for the main board revision ID, and use the table above, however it's also possible to determine the right kit by identifying the model in other ways.

First of all, the console shell revision.  As far as this mod is concerned, there are only 2 revisions.  The first is the "full-size" shell, which looks like this, depending on region.

The second shell revision is the one sometimes referred to as the "SNES Jr" or "SNES Mini" (not to be confused with the recent "SNES Classic")

In addition to the shell revision, you will need to know the revision of the sound chip in your console.  For this, you'll need to open the console and look at the main PCB (unless you have a model 2 console, in which case you are guaranteed to have the single "S-APU" revision sound chip).  There are two options.  The older revision consists of several separate chips, two of which are labeled "S-SMP" and "S-DSP".  This includes the earliest revision boards which actually had a completely separate and removable sound module inside of a metal case.  The newer revision consolidated these chips into a single package labeled "S-APU".

Installation

APU Crystal - All models

Remove the ceramic resonator near the APU, labeled X2, and replace it with the provided crystal oscillator.  Next, remove 1 or both of the load capacitors next to the oscillator (look for traces going to the 2 legs of the oscillator to identify the right capacitors, they should be VERY close, but are sometimes on the bottom of the board), and replace them with the ones provided in the kit.  These capacitors are really tiny and easy to lose, so be careful with them.  The kit comes with 1 extra just in case.

Load capacitor reference designators:
SHVC-CPU-01: C14, C15 (Inside removable APU module)
SNS-CPU-GPM-01/02: C71, C72
SNS-CPU-RGB-01/02: ?
SNS-CPU-APU-01: ?
SNS-CPU-1CHIP-01/02/03: C55, C56 (Bottom of PCB)
SNN-CPU-01: C44, C45 (Bottom of PCB)

Encoder - Discrete S-SMP + S-DSP (Early model PCB's)

COMING SOON

Encoder - Combined S-APU (Later model PCB's)

Using the provided double-stick tape, carefully attach the encoder PCB on top of the S-APU chip.

Insert small wires into the 5 numbered holes in the PCB from the top and solder them into place, leaving a few cm of length sticking out the top.  You can use 30AWG Kynar or magnet wire, but I've recently switched to using clipped off resistor legs.  The ability to bend them into place and have them stay where you put them makes the next step much easier.

Bend the wires down to the corresponding pin, trim them to length, and if you're using insulated Kynar wire, carefully strip off just a small bit from the end of each wire.  If you're using resistor legs, slip a small length of shrink tubing over pin 93 to insulate against the adjacent wires.

Now comes the hardest part of this entire mod.  Solder each wire to the corresponding chip leg.  Double check that you are attaching to the correct leg using the silkscreen numbers to help count pin numbers.  Ensure that you have a good solder fillet, and that there are no solder bridges.  Go slowly and use plenty of flux.  Magnification and good lighting are extremely helpful.

Transmitter - Model 1 consoles

COMING SOON

Transmitter - Model 2 consoles

Desolder rear I/O panel

The trickiest part of the transmitter installation is drilling the hole for the output port.  I suggest starting the hole from the inside of the I/O panel.  Your target is the spot where the vertical reinforcement ridge meets the angled "lip".  See the photo below, following the red crosshair, NOT the hole shown in the photo.  Start the hole with a smaller (~1-2mm or so) drill bit an angle it downward into the corner formed by the angled "lip" in order to ensure that the center of the hole stays in that corner.  DO NOT DRILL ALL THE WAY THROUGH THE SHELL AT THIS ANGLE.  Once the hole center has been established, straighten out the bit (still using the smaller bit) so that it is perpendicular to the shell, and finish the hole all the way through.  Check that the hole is properly centered by dry fitting the TX board.  Adjust if necessary.  Once you're satisfied with the hole placement, enlarge the hole to size with a 5.5mm (7/32") drill bit from the other side of the panel (outside-in).  Dry fit the board one last time to confirm the hole size and position.  Adjust with a needle file if necessary.

Reassemble the rear I/O panel, but don't re-solder it yet.  Insert the included pin headers into the matching holes in the SNES board.  The 3-pin header goes where the non-existent RF module would have gone, and the 2-pin header with a space in the middle goes into a pair of vias in the ground plane of the RF module footprint.  Refer to the TX board if you're having trouble.  Next, install the TX board and hold it in place using the I/O panel screw.  Adjust things as necessary, then flip the PCB over and solder the 5 pin header pins.  The 2 ground pins are very difficult to solder because the vias are not thermally isolated.  Take your time and use plenty of flux.  Confirm that the ground pins are making good electrical contact using a multimeter, as well as physical contact by attempting to wiggle them.

Flip the board right-side up again, make sure everything is properly in place, and solder the TX board to the header pins.  Finally, flip the board over one more time and re-solder the power connector pins to the I/O shield.

Finally, connect the encoder to the TX board using the provided wire.  Simply connect + to + and - to -, following the PCB markings on each.  Cable routing differs by console revision.  Revisions with the APU behind the cart slot are more or less a straight shot.  Revisions with the APU in front of the cart slot typically run the wire from the APU to the left of the board, hook underneath the left side of the cart slot, then back up to the TX board.