This is an adaptor that plugs into the PS1 parallel port and provides a digital audio output via optical or coax (cables not included). The pure 44.1KHz/16bit digital audio is picked up before the internal DAC, eliminating any noise caused by the circuitry inside the PS1.

While there are other digital audio mods for the PS1, they require a lot more effort (and soldering) to install, and don't provide a good way to mount the output jack - either glue it on the back of the PS1, or cut a hole. So I set out to find an easier and cleaner way, and after a bit of research it just so happens the parallel port found on earlier PS1 models already provides most of the required signals. There are however 2 signals that are missing, but as luck would have it, there are 2 pins on the parallel port that are free (not connected).

That means this mod does require soldering 2 wires (included) inside the PS1 to take those signals from the mainboard to the parallel port. But the points to solder to are relatively easy to find and don't require any special soldering skills or equipment.

Compatibility:

It is only compatible with board revisions PU-7 up to PU-20 found inside following PS1 models:

SCPH-100X, SCPH-300X, SCPH-350X, SCPH-500X, SCPH-550X, SCPH-700X, and some SCPH-750X that have the PU-20 board inside (it will not work with PU-22 boards which are also found inside the 7500 series so double check yours first).

Please note this is not compatible with PSIO modded PlayStations. Not only does the PSIO already occupy the parallel port, but it also re-routes a bunch of signals going to the port. However this is compatible with X-Station modded consoles.

As this outputs a standard 44.1KHz/16bit digital audio signal, it should be compatible with any external DAC, receiver or upscaler (like the RetroTink 4K and OSSC Pro) that accepts digital audio. While I have tested it with a number of devices without issue, I do not have either of those upscalers so they remain untested at present.

Parts/tools required:

• Soldering iron and solder
• JIS/Phillips head screwdriver
• For coax output: A 3.5mm to RCA cable (if using a stereo cable, the digital audio will be on the left channel)
• For optical output: A 3.5mm to TOSLINK adaptor or cable

Installation:

• Open the console by removing the screws on the underside and lift off the top shell (make sure you don't have a disc in there).
• Carefully unplug the connections to the optical assembly, power supply, controller ports and set aside the optical assembly.
• Remove the screws holding the top metal plate (on the SCPH-100X you will also need to remove the controller ports).
• Lift the metal plate by grabbing it at the rear of the console and pulling up and towards the front.
• For PU-7, PU-8, and PU-18 boards, remove the remaining screws holding the mainboard and remove the mainboard.
• For PU-20 boards, lift the copper shield and fold it back over the metal sheild on the mainboard.
• Solder the 2 wires from the points on the mainboard to the pins on the parallel port (see images above).
• Reassemble the console, plug in the adaptor and hook it up to your amp.
• Crank the volume and party like it's 1999!