Electronic – Using audio isolation transformer to clean power to a Raspberry pi

audiopower supplyraspberry pi

I want to "clean up" the powersupply to a raspberry pi that I am using for audio recordings.

I am getting a lot of low frequency buzz, i.e. 60 to 2000 hz.
I am wondering if I can use an 1:1 audio transformer to reduce the interference from the PSU to the pi, alternately to isolate the usb-soundcard power that I suspect may also be culprit.
The pi PSU is 5.1v 3A
THis is the transformer:
Max voltage: 100V

  • Isolation coil+coil: 100Mohm min
  • Dämpning Dampening: 2.5dB max (1kHz)
  • Primary impedans (1kHz): 600ohm ±5%
  • Secondary impedans (1kHz): 600ohm ±5%
  • Primary DC-resistans: 50ohm ±5%
  • Secondary DC-resistans: 60ohm ±5%
  • Primär induktans (1kHz): 310mH
  • Sekundär induktans (1kHz): 330mH
  • relationship: 1:1

(please excuse my poor translation of technical terms)

EDIT

From what I have gathered in many posts poor power supplies(PSUs) can give interference in auxiliery equipment plugged into the Pi, e.g via USB or GPIO.
As for audio the answer to this post gives an example of a homemade PSU that provides "clean" power to the RPI to improve sound recording. However, this is takes a little too much space for the project I working on (networked wildlife cameras). Theoretically using powerbanks should be better than regular PSUs but powerbanks have their own step-up or step-down circuits that I find give as much intereference.

What I am looking for is a simpler, "good enough" solution to filter power to either the Pi or the USB soundcard so that I can remove some of the noise in region I want, i.e. 50 to 3000 Hz. How can I create a filter from 50 to 3000Hz?

Is the culprit likely to be the PSU or the pi itself?

Should said filter be placed between PSU and pi, or between soundcard and pi?

Best Answer

Probably the black_brick power supply is your problem. Those supplies have a large capacitor (several nanoFarads) from primary to secondary, so as to pass the FCC interference tests. But lots of fast-edge trash also gets coupled from secondary to primary, and like all charges,

  • will explore and use ALL POSSIBLE PATHS to get back home

To block those charges, you need a common_mode filter, and possible differential_PI L+C filters (here "differential" means FerriteBeads in both

  • DC_GROUND

and in

  • DC_RAIL

Those black bricks are cheap, and you get the noise_supression you have (not) paid for. So you get to add noise suppression.

Related Topic