I would actually hazard a guess that the noise is on the 3.3V rail that is fed up the FFC to the display. Displays generally only use the 5V for the backlight as that is where most of the power is consumed.
I've found the schematic for the DigiAmp+. The TAS5756M that it uses does use the Pi's 3V3 rail for the digital processing, and then has a 12-24V rail for the amplifier side. It has both an inductor and reasonable level of smoothing capacitor on the 3V3 rail, so I wouldn't have expected that much noise to be backfed.
Adding additional capacitance to the 3V3 handling on the display would be the place I'd look.
The DigiAmp+ uses a standard TI TPS54302 step-down converter, so generally those wouldn't be too noisy as long as they have sufficient smoothing and filtering. An oscilloscope on the rail would give you some indication of the regulation on the rail.
Another thought is whether the 12-24V power supply you're feeding into the DigiAmp+ can cope with the rapid changes in demand.
I've found the schematic for the DigiAmp+. The TAS5756M that it uses does use the Pi's 3V3 rail for the digital processing, and then has a 12-24V rail for the amplifier side. It has both an inductor and reasonable level of smoothing capacitor on the 3V3 rail, so I wouldn't have expected that much noise to be backfed.
Adding additional capacitance to the 3V3 handling on the display would be the place I'd look.
The DigiAmp+ uses a standard TI TPS54302 step-down converter, so generally those wouldn't be too noisy as long as they have sufficient smoothing and filtering. An oscilloscope on the rail would give you some indication of the regulation on the rail.
Another thought is whether the 12-24V power supply you're feeding into the DigiAmp+ can cope with the rapid changes in demand.
Statistics: Posted by 6by9 — Wed Dec 03, 2025 11:49 am