Noise from Raspberry Pi4 USB - Solution?

Hi everyone
I’m Peter.
I apologize for my English (I use Google translate from Italian).
I am writing to you for advice regarding an electrical noise problem.
I’ll explain.
My music listening is exclusively through headphones.
In this regard, my audio setup is configured as follows:
Headphones: Sennheiser HD820.
Roon Rock server on an intel NUC10-I5;
Roon endpoint: RPI4 Rev. 1.5 (powered by Ropiee OS – I wanted to test that VITOS by Silent Angel but it is not compatible with my RPI4 model);
DAC: Denafrips Pontus (first series with Amanero DSP card that supports native DSD up to 256 – PCM up to 384) connected to RPI4 with Wireworld Starlight USB cable.
Pure Class A Headphone Amplifier – Single Ended – triode configuration: Icon Audio HP8-MKII – revalved with pair of CV1988 KB/FE - 6SN7GTY (Black Graphite) Brimar.
VAN DEN HUL D-102 mk III amplifier DAC connection cables terminated RCA.
The amplifier has three selectable impedance levels: L M and H.
Low 8-40 Ohms (nominally 16)
Med 30-300 (nominally 100)
High 250-1000 (nominally 600)
Although the nominal impedance of the HD820 is 300 Ohms, I prefer to use the H mode of the amplifier as the bass is more full-bodied.
Normally with the DAC both off and on but with the Raspberry still off, in the headphones I can only detect the electrical noise of the amplifier’s output transformer. I can say that this noise is almost imperceptible when the LOW mode is selected as the impedance of the headphones on the amplifier, while it becomes more and more perceptible when the impedance M and H are selected.
But that’s not the problem. When I turn on the Raspberry (currently powered by its original Power Supply) by increasing the volume knob (only from 14 o’clock onwards) I start to hear a rather strong hum that dominates the background noise of the amplifier transformer. This RPI turn-on noise is always the same and is independent of the selected impedance mode.
I hope you have been clear in describing the problem and now I ask for useful advice on how to suppress that annoying background noise generated by the RPI4.
I had thought of inserting a DDC (Gustard 18 – Singxer SU-6 or Denafrips IRIS) between the RPI and the DAC and then connecting to the DAC with I2S.
Thanks in advance to anyone willing to contribute.

I recognize that problem. I could not solve it with a better powersupply and ended up with mounting a Hifiberry Digi+ and connecting my DAC to the digital output (coax or optical) of the Hifiberry.

1 Like

@Ron_Witkamp’s suggestion is, I suspect, the fail safe solution.

Issues like this can be really hard to solved - but you could try:-

  • Changing cables (perhaps just to cheap ones for testing) - missing/ dirty earth connections can cause issues like this.
  • Try moving the PI further away from the amp and DAC
  • Try switching PI power supply.
  • I think the Pi USB earth is floating - so this might not help - but an Intona USB isolator can help if there is a galvanic isolation / ground loop issue with the USB connection.