Audio noise issues

[Hans]

Hi,

 

when I power the RetroCade Synth through a USB port that is connected to my main Audio machine, I have audible audio interference (high-pitched hissing, noise).  This is independent of the USB port that I use, either directly on the machine or on a hub.  When I power the synth through an external power supply, that noise is not present.  I wonder if there is a way to get rid of this?  Is this because the ground plane of the USB, by the way of the USB cable powering the board, is shared with the audio ground plane of the output jacks?

 

I would like to keep the board connected to my computer so that I can reconfigure it and experiment with sketch changes, but the noise makes it kind of impractical.

 

Any help would be appreciated!

 

Thanks,

Hans

[Jack Gassett]

Hans,

 

This is strange, I'm not sure what could be causing this issue. Can you try to power it through a USB Hub? Particularly a powered USB Hub?

 

Thanks,
Jack.

[andymanone]

Hi Hans,

 

I´ve the same issue like you,

 

but if I switch from the "Welcome" Screen via Joystick to the next menu , the noise is off.

 

I recognized, that the noises comes from the animated "Space invader" on the start screen...

 

 

andY

[Hans]

Jack,

 

I tried powering the board both through a high-quality powered USB hub and through a direct USB port on the machine.  With both, the noise was clearly audible.  When I used an external power supply, there was no issue.  In a performance situation, there'd be no issue with using a separate power supply, but for development, the approach won't work.  I'll try powering from an extra laptop tomorrow, just for another data point.

 

I kind of suspect a ground connection issue, but I'm not much of an electronics buff.

 

-Hans