Hi there,
I built a boom box using a TPA3118D2 in a mono setup (input channels strapped together), accepting a signal from a phono jack. The power comes from 6 battery cells with a BMS. So far so good.
Then I decided to add a self-standing audio source and I installed a Raspberry Pi Zero W (Wi-Fi version), also powered by the same battery pack via a DC-DC converter (22V->5V), connected to a DAC . I added a source toggle to be able to switch between line input and RPI.
This created a quite loud interference in the loudspeaker. The interference is audible when both the amp and the RPI are on. The volume doesn't change the intensity of the noise. I noticed that the noise increases with the RPi activity, so I'm guessing that it may be somehow tied to the current draw of the RPi. I don't think it is the WiFi radio signal, or at least not only that, because even commands that cause CPU and flash drive activity but no network activity create interference.
I tried grounding the signal and various points to the metal plate, and to move the DC/DC converter, DAC and RPi away from the amp and loudspeaker wire, but that didn't change anything.
Does anybody have any suggestion on how to reduce or eliminate the noise?
EDIT: Disconnecting the Pi but leaving the DC/DC converter on, and connecting different loads (motors, LED) to it does not produce noise.
Thanks.
I built a boom box using a TPA3118D2 in a mono setup (input channels strapped together), accepting a signal from a phono jack. The power comes from 6 battery cells with a BMS. So far so good.
Then I decided to add a self-standing audio source and I installed a Raspberry Pi Zero W (Wi-Fi version), also powered by the same battery pack via a DC-DC converter (22V->5V), connected to a DAC . I added a source toggle to be able to switch between line input and RPI.
This created a quite loud interference in the loudspeaker. The interference is audible when both the amp and the RPI are on. The volume doesn't change the intensity of the noise. I noticed that the noise increases with the RPi activity, so I'm guessing that it may be somehow tied to the current draw of the RPi. I don't think it is the WiFi radio signal, or at least not only that, because even commands that cause CPU and flash drive activity but no network activity create interference.
I tried grounding the signal and various points to the metal plate, and to move the DC/DC converter, DAC and RPi away from the amp and loudspeaker wire, but that didn't change anything.
Does anybody have any suggestion on how to reduce or eliminate the noise?
EDIT: Disconnecting the Pi but leaving the DC/DC converter on, and connecting different loads (motors, LED) to it does not produce noise.
Thanks.
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Do a web search for lm2596 or whatever that power supply uses, and raspberry pi, you’ll get more answers as to how and why that may not be a good thing.
Can probably test it further using a dedicated power supply to the raspberry pi.
After you get the power supply sorted out, it may be necessary to use some shielding between some of your boards to reduce interference also, if you have issues with dropouts
Can probably test it further using a dedicated power supply to the raspberry pi.
After you get the power supply sorted out, it may be necessary to use some shielding between some of your boards to reduce interference also, if you have issues with dropouts
Yes, it's an LM2596. I'll do more research on it. I was hoping to not have to add more batteries in an already busy layout, but I can easily test with a separate wall wart.