This mod grabs the pure 32KHz/16bit digital audio from the full size Super Nintendo and Super Famicom (not the SNS-101/SFC Jr.) and outputs it as S/PDIF over coax or optical, allowing external DACs and receviers to decode the digital audio stream from the SNES with better clarity and zero noise. This is unlike the original analog audio from the SNES which has poor frequency response and is prone to noise and interference.

As the board occupies the same space as the RF modulator, it is required to remove the RF modulator to make room for the digital audio board. This allows the digital audio output jack to use the exisiting RF output hole in the case, making this a no-cut mod. This mod is fully reversible should you ever wish to reinstall the RF modulator (provided you didn't immediately throw it away).

As this mod only relies on the DSP/APU sound chip to be working correctly, it may be used to bypass a faulty analog audio stage (if for instance your SNES has a broken DAC or LM324/S-MIX chip). However it is highly recommended to confirm the original analog audio output is working correctly before installing this mod. If you do not have proper audio before installing this mod, there is no guarantee the digital audio output will work.

It is also highly recommended to replace all the electrolytic capacitors in your console if you haven't already. This is especially true for the SHVC models as they will almost certainly have leaking capacitors.

Compatibility

This mod is compaitble with all SNES/SFC board revisions expect for the Mini/Jr models as these do not have an RF modulator.

Super Game Boy (SGB) and MSU-1 audio is not output over digital S/PDIF. The Super Game Boy and MSU-1 audio is converted to analog inside the cartridge itself and does not get output as digital audio from the SNES. This digital audio mod does not affect the analog audio from the SNES and all analog audio including SGB and MSU-1 audio will still be available via the multi-out connector.

Be aware this mod, like similar SNES digital audio mods, is not guaranteed to be compatible with all receivers or DACs. This appears to be due to the SNES pausing the digital audio stream when no audio is being played back which can cause some DAC's to dropout, and depending on the game this can happen mid-song (the Super Mario World title screen music does this a lot). From my own tests I've had an 85% success rate with only one device (Pioneer VSX-920) suffering regular audio dropouts. Unfortunately there is no known fix for this so you may need to try a different receiver or DAC if you have issues.

Parts and tools required

• Soldering iron and solder
• Desoldering braid/solder sucker
• Wire strippers
• Basic multimeter
• 4.5mm Gamebit driver and JIS/Phillips head driver
• Mini TOSLINK to TOSLINK cable for optical output, or 3.5mm to RCA cable for coax output (note if using a stereo cable the red/right plug is not used)

Installation:

Before doing any work on your console make sure to turn it on for a second with the power unplugged, this will ensure all capacitors inside the console are discharged

See below for a detailed video, or read on if your prefer written instructions.

1. Remove the 6 gamebit screws from the underside of the console. Lift off the top shell, unplug the power switch and controller ports. Note where the spring is installed for the eject mechanism on the left and then remove the eject mechanism by lifting it up and to the right.
2. Remove all screws from the mainboard (on the SHVC models one screw is hidden under the sound module).
3. Lift the mainboard out of the bottom shell and remove all screws on the underside, take note one screw will be slightly longer than the rest, we will need this again soon. Remove the single screw holding the 7805 voltage regulator to the heatsink and set the heatsink aside.
4. Desolder the 4 pins on the underside of the mainboard going up to the RF modulator. Note the rightmost pin is connected to a ground fill and may put up more of a fight.
5. Flip the board over and remove the RF modulator, it should come out without any force. If you feel any resistance, double check that all four pins have been desoldered properly and you removed all the screws.
6. Prepare the digital audio board by installing the included white spacer from the underside in the left "ear" (the hole without the plating around it). It should hold itself in place without falling out.
7. Place the set of 4 pin headers in the holes left by the RF modulator with the shorter side facing up. Then place the digital audio board on top, making sure the pin headers poke up through the board, do not solder anything yet.
8. Take the slightly longer screw that was holding the original RF modulator and stick this through the right ear of the digital audio board from the topside.
9. Fix the included nut to the underside (finger tight will do) making sure the output jack is centered horizontally with the case hole. Note it will sit slightly higher up in the hole but this is as low as I could get it.
10. Once you are happy with the position and have confirmed the white spacer is still in place in the left ear, proceed to soldering the pin headers to the digital audio board and the underside of the mainboard. SHVC ONLY - expose the 5 via's inside the SHVC sound module (see images), this can be done by gently scraping the blue coating off them with a metal tool and running some fresh solder over them and wicking it off with braid (this may take a couple of passes).
11. Plug in the 5 wire connector (if you opted for the board with the connector) and begin wiring the 5 connections required for the digital audio mod. See above images for the most convenient place to find the required signals and try to keep the wires fairly short (leave a bit of extra slack if you're dealing with the SHVC model as the wires need to exit the sound module from the top left corner). note connections numbered 4 and 5 on the digital audio board are swapped on the non-connector boards, make sure you go by the DSP/APU pin numbers
12. Double check your wiring and make sure there's no shorts, incorrect or poor connections.
13. Give the console a quick test by plugging in the power switch, a known working game, and power (make sure the SHVC sound module is plugged in for SHVC boards). Turn on the console and check to see if there's a red light on inside the 3.5mm digital audio output jack. If you see no light, try a different game. If you still don't see a light, unplug the console, turn on the power switch to discharge the capacitors and recheck your connections to the digital audio board. Do not run the console for more than a couple of minutes without the 7805 heatsink.
14. Once you see the (red) light, unplug power, flick on the power switch to discharge the console again and proceed to reinstalling the heatsink. Screw it in from the underside first, and then screw down the voltage regulator. You will end up with a spare (free!) screw as the RF modulator used an extra screw which we will not be needing.
15. Reinstall the mainboard into the bottom shell. Note the hole on the digital audio board with the spacer takes one of the longer screws - do not overtighten this one. Another long screw goes just to the right of the multi-out and the remaining two hold the cartridge slot. If dealing with an SHVC model don't forget the sneaky screw that needs to go in under the sound module.
16. Plug in the power switch and controller ports. This would be a good time to give it all a proper test. Connect everything including the digital audio output and make sure both the analog audio output and digital audio are working correctly. If you get intermittent drop-outs or no sound with the digital audio, try a different DAC/receiver. Remember due to the nature of the digital audio stream coming from the SNES it is not guaranteed to work with all devices.
17. If everything is working as expected reinstall all the remaining screws (RF shield is optional). Screw in the power switch last and then reinstall the cartridge eject mechanism.
18. Throw the top shell back on, stick the gamebit screws back in the bottom and enjoy your crystal clear SNES soundtracks!

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