Advanced soldering skills required

This modification board 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, 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 this board is designed to re-use the original RCA connector on the SNES, it is required to remove the circuit board inside the RF modulator to make room for the digital audio board. This means the old RF output will be disabled and instead the RCA jack is used for the S/PDIF coax output, allowing easy connection to your receiver or DAC without any case modifications.

Note the digital audio is output via coax only, however it is possible to use a cheap coax to toslink converter if optical is required or preferred.

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. The 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.

Also be aware that 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, and depending on the game this can happen multiple times per second, even mid song. 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, but I have had success using this external DAC. Please keep in mind it is from AliExpress so the components used in these may change without notice and no longer work with the SNES digital audio.

Parts and tools required

• Soldering iron and solder
• Desoldering braid/solder sucker
• 4.5mm Gamebit driver and JIS or Phillips head drivers
• 1 metre of single core 30AWG Kynar wire (INCLUDED)
• Small pry / hook tools or a small flat-head screwdriver

Installation:

• Remove the mainboard from the SNES/SFC and unscrew the heatsink attached to the 7805 voltage regulator (and the SHVC sound module if dealing with an SHVC board).
• Remove the top cover of the RF modulator. A small pry tool or flat blade screwdriver should easily take care of this.
• Desolder the RF modulator circuit board (not the entire RF can). There are 4 through hole pins connecting the RF PCB to the mainboard towards the front, one connection to the RCA jack in the rear right corner, and two or three blobs of solder connecting the RF PCB to the RF can.
• Remove the RF PCB. Be careful with this if you ever want to reverse the mod, make sure you've properly desoldered all the connections listed above. There should be a gap in the PCB around the RCA jack, you can insert a flathead screwdriver or prefrebly hook tool to pry up the PCB. If you're not worried about ever going back to RF, you can be a little rough with this ;-)
• With the RF PCB removed you should be left with the 4 pins from the mainboard and the centre pin of the RCA jack left over. Install the digital audio PCB making sure the 4 pins and the RCA pin stick up through the PCB (you may need to bend the RCA pin a little if it does not line up).
• Solder the 4 pins and RCA connection, then the 3 exposed pads around the outside of the PCB to the RF can.
• Finally connect the 5 signal wires from the mainboard to the pads on the digital audio PCB. Refer to the images above for connection points on your SNES/SFC revision. The digital audio PCB lists the pins of the DSP/APU to connect to, you are free to solder directly to these pins but I have alternative (shorter and easier to solder points) in the images above.
• Double check your work and there's no shorts or poor connections, be sure to reinstall the heatsink before testing or the 7805 will get very toasty!