Power supply noise problem.

[Bjarnevip]

Hi

I have build a reciewer containing a RaspberryPI 3B, a IQAudio PI_DAC+ and a Yuan-Jing (YJ) Blue/Black 2.0 Board( with modufication from this linkhttp://www.diyaudio.com/forums/diyaudio-com-wiki/252663-tpa3116d2-boards.htm).

For PS I use a laptop PS 19V5 output directly to amp. and a UBEC 5V/3A DC-DC converter. for the PI.

It's grounded to the chassis.

I this constellation I have a lot hiss and noise in the loudspeakers.
If I use a USb PS instead of the UBEC, it's gone ...no noise.

Can anyone tell me what is wrong with the UBEC?
I have measured the AC on the 19V5 and it's about 20mVAC and for the UBEC it's about 2mVAC.

Thanks in advance

Bjarne

 

[Domenicus]

Both PS have the same ground and your PI is connected to the amp via line-in/out. That's nice little ground loop. You could use a ground loop isolator between PI and amp.

 

[abraxalito]

DC/DC converters create noise on the supply that feeds them. This seems a possible cause of your problem.

 

[Jerms]

Either need a separate 5V mains supply for the Pi or a ground loop isolator in the audio inputs to the amp from the Pi.

There are isolating DC/DC converters available for around £10 which do 1.5A output. This might be enough for a Pi3 or it may not!

 

[Yatsushiro]

I had exactly the same problem on a similar setup.

I was able to fully cure it by using one of these:

https://www.amazon.co.uk/gp/product/B015E4835U/ref=oh_aui_search_detailpage?ie=UTF8&psc=1