ProtoDAC TDA1387 X8 project

[kookedtweeter]

Are you using ethernet or WiFi? With some of the prototypes built on perf board, WiFi was picked up. Nothing playing it is a periodic noise. With a file playing there is a more of a continuous,  pulsing noise. The PCB has a ground plane, and I have not heard it with the PCB. There also might be a bad solder joint that could act as a diode, and pick up RF.

I am using wifi on a raspberry pi 5.
I had this on a raspberry pi 3b as well, and the board and parts were a kit purchased off ebay. It has "ProtoDAC TDA1387 X8" masked on the board and the whole board in general does not look prototype ish.

It does seem to be some communications transfer because I booted the PI with the DAC installed and no SD inserted. I seen a few blips on the scope but then it was relatively quiet with the occasional tiny 5mv blip. As soon as I power it up with an SD card inserted, the noise begins. I don't believe wifi or bluetooth related though because I ran 'rfkill block all' and still get the same noise. Its on the 5v power from the PI. I originally thought it was just the output, but it seems its transferring through from the 5V.
Unless 'rfkill' doesnt actually turn the hardware off, i dont think its the wifi or bluetooth causing this.

I also scoped the power pin on the PI itself with the DAC not installed and PI fully booted and the 5V supply is dead silent.
Both tests are being powered by a battery back, so no adapter switching noise.

Any ideas what it might be, or how to remove the noise?

[hifinet]

The "ProtoDAC TDA1387 X8" PCB has a ground plane. I would try powering ProtoDAC from a separate source. Use a stacking header with GPIO pins 2 and 4 removed, so ProtoDAC doesn't get power from the GPIO. Then use another 5V supply and apply power to the pads between the RCA jacks. You can also use DuPont jumpers instead of the stacking header from the RPi GPIO connecting 6, 12, 35 and 40. Keep the length of the jumpers 10cm or less.

If the noise is still there, the final possibility could be that it is coming from the TDA1387 module. It might have a single defective chip, bad solder joint, etc.

[kookedtweeter]

The "ProtoDAC TDA1387 X8" PCB has a ground plane. I would try powering ProtoDAC from a separate source. Use a stacking header with GPIO pins 2 and 4 removed, so ProtoDAC doesn't get power from the GPIO. Then use another 5V supply and apply power to the pads between the RCA jacks. You can also use DuPont jumpers instead of the stacking header from the RPi GPIO connecting 6, 12, 35 and 40. Keep the length of the jumpers 10cm or less.

If the noise is still there, the final possibility could be that it is coming from the TDA1387 module. It might have a single defective chip, bad solder joint, etc.

Ok, so i painstakingly desoldered the entire header...why did i solder ever pin lol.
Powered the dac externally and its quiet.
The noise is comming from the PI itself. When i scope the 5v on the gpio header i see the same noise as before. So the pi is givng me a bad 5v out.
Well good to know its not the dac.