Why is my computer screwing up my Nintendo Switch audio when it's powered off?

[LloydLynx]

When I sway "switch", I mean the circuit kind of switch. When I say "Nintendo", I mean the Nintendo Switch console. Make sense? Continue reading.

 

I have a home made USB switch that switches a DAC between the Nintendo and the PC. Here's the schematic.

Spoiler

The Issue:

The Nintendo's audio sounds like bit rot if the PC is powered off and the switch is going to the Nintendo. When I unplug the USB from the computer or turn the computer on, the Nintendo's audio then works fine.

The reverse is not true when the PC is playing audio and the Nintendo is off.

Something about the computer being turned off but still physically connected is screwing up the USB signal, but why?

 

 

[Alex Atkin UK]

25 minutes ago, LloydLynx said:

When I sway "switch", I mean the circuit kind of switch. When I say "Nintendo", I mean the Nintendo Switch console. Make sense? Continue reading.

 

I have a home made USB switch that switches a DAC between the Nintendo and the PC. Here's the schematic.

  Reveal hidden contents

The Issue:

The Nintendo's audio sounds like bit rot if the PC is powered off and the switch is going to the Nintendo. When I unplug the USB from the computer or turn the computer on, the Nintendo's audio then works fine.

The reverse is not true when the PC is playing audio and the Nintendo is off.

Something about the computer being turned off but still physically connected is screwing up the USB signal, but why?

 

 

You've probably created a ground issue as the Switch has no real ground, but the PC does.  You need to switch EVERY line and it be a really good quality switch that isn't going to cause any signal leakage.

This is not simple, I had a lot of problems with HDMI switches in the past because they weren't good enough.  It tends to be the active ones that work best as manual switching can causes losses and interference.  Not sure how USB ones usually do it, I've avoided them for this reason.

[Heats with Nvidia]

You also didn`t switch the -Data line. The switched off computer might mess with that. I would keep the ground connection if neccessary, but if possible, switch all of the connections.