Split a single power source to act as two independent power sources?

Question

Disclaimer: I'm very new to electronics.

I am building a Bluetooth speaker using an ESP32 dev-board and an I2S DAC which outputs to the audio-amp and then the speakers. I am using a 12 V, 3 A adapter to power everything. The ESP32 and DAC are run off of a single buck converter. Music came through but with a lot of noise.

After some research I was able to reduce some of the noise with a common ground for everything, but there is still "processing" noise from the ESP32: fuzz when connected to BT, faint squelching beeps and clicks between songs and when paused.

However, I made a breakthrough today when I powered the ESP32 from the 5 volt USB-C, while leaving the DAC and amp connected to the adapter. All of the processing noise is gone and it's dead silent when paused, connecting, etc..

So my question is: How can I achieve the same result with the single power adapter and using the pins to power the ESP32 (and skip USB-C)?

Update: Dedicating a converter to both the ESP and DAC along with running the wires directly to the source and ground worked like a charm! I'm going to put in an order for some filters to see if I can make it even better! Thanks for all the info!

Answer 1

First, with things all common-grounded, make sure that each device has its own ground wire all the way back to the power source. Anywhere two device currents are sharing the same piece of wire is a source of noise contamination.

Second, do the same thing with the 5 V or 3.3 V lines - no sharing.

Third, add an inline noise filter to each of the 5 V, 3.3 v, or whatever power lines.

Update:

Ideally, the DAC should have a linear regulator. The next thing to try after you are sure each device has home runs back to the power source is to add filter capacitors at the output of the source and at each device input. These should be as close to the output and input connections as possible, with the shortest possible leads. Start with a 0.1 uF ceramic and a 10 uF to 100 uF electrolytic, with the ceramic the closest part.

I'll do some surfing to find something on ebay or Amazon. Do you know the approx. current requirements for each of the devices?

Please add a wiring diagram to your post that shows the various power supplies, voltages, and devices, and all connecting wires.