PS1 TOSLINK mod + PS1 Digital


Hello! I just finished installing Dan's Saturn/PS1 Toslink mod and wanted to share my findings!

The Toslink port works perfectly, but it seems that digital audio out of the HDMI will stop working with this mod installed. Analog audio still works great.
I'm not overly fussed as I can't use the digital audio out of the HDMI for my set up anyway.

Before I installed the mod Dan told me over email that there may be too much capacitance draw? I imagined that both the TOSLINK and HDMI audio would stop working if that was the case but perhaps not!

Does anyone have any ideas?

Hopefully this is useful for anyone else in the same boat as me :p


Staff member
There is 1k termination resistors on the SPU, Pins 97,98,99 of the PS1 motherboard. Try lowering the resistor values and see if this helps.



Thank you very much for the reply Dan!! I've just ordered some 750 ohm resistors, when they arrive i'll give it a try and report back!

Just to make doubly sure for my PU20 board, its these ones here in the red square right?

Thanks! :)



I had some left over 750 ohm resistors from an old project, but unfortunately they result in the same problem :(
I've got some more 330 ohm resistors on the way, once they arrive in about 1 to 2 weeks i'll give them a try! :)
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So I just finished putting in the 330 ohm resistors but unfortunately it seems at some point I broke the 2nd and 3rd from the right connections on the audio flex. I have no idea when it happened, so for all I know the mods might have worked with the 750 ohm or even the stock 1k resistors... :(

The connections look great under magnification but I'm guessing theres a hairline crack where the pad connects to the trace on the cable. I tried resoldering them but it didn't work.
As for right now i'm getting digital audio from my toslink and the video is fine with the 330 ohm resistors in.

My question is wether I would be fine leaving the 330 ohms in? I'm worried that the extra current might damage the DAC or something. Any ideas?

Sorry for leading you on a wild goose chase! I might buy another set of flexes and re-do the audio cable at some stage and try again.


Hello!! Sorry for taking so long on this. I've finally replaced the audio flex as well as putting back the stock 1000 ohm resistors. Both the TOSLINK mod and the PS1 digital audio will work simultaneously with the stock resistors in place :)

Thank you Dan for all your help!! :)