Hi @homme_de_terre / Manfred and @Steve1 ,
Just hopping into the topic, responding to Steve’s reference to one of my older threads on the forum.
My issue was a ‘ticking’ noise, but it was quicker than one tick per second. Maybe like 4 or 5 per second, which made it sound more like a ‘ripple’ noise.
First I also thought it was an EMI problem. And I experimented with all types of foil. Sometimes it helped, but it was never completely gone.
In the end I found out that the Mini uses a MCU-chip with an integrated DAC. In fact the MCU handles all the ADC/DSP/DAC/BT functions, so a system-on-one-chip design. If you remove the top board of the Up2Stream Mini, the MCU/DAC chip is visible.
The fact that MCU and DAC are combined in one chip, makes it sensitive to pick up noise and create the ripple.
I then tested by adding the optional DAC board. This one by-passes the DAC in the MCU/DAC combination. And the result I found …. ripple completely gone.
More info about my search, tests and results can be found here: Up2Stream Mini & Ripple problem ? - #36 by KolfMAKER