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I am working with a bluetooth audio circuit. I am facing noise problems in the mic input so I used B0505S DC DC isolated module. It worked but now when I printed a PCB of the same circuit and I am using it I am getting the noise problem again. Now when I power my circuit from the laptop USB port there is no noise problem in the mic input but when I power it from a battery I am getting noise problem again. It is really strange that when the supply is from USB port of the laptop there is no noise but when I connect a battery to power he circuit I get lot of humming noise. The bluetooth is getting its power from the 3.3vout of the LDO from Teensy arduino board. I read online that someone used a REG711 switching regulator Switched-Cap DC/DC Converter because when he used it his noise problem went away. I tried to power my circuit through a stepup regulator Polulu 3.3V step up voltage regulator but still there is the same noise problem. I read online that using LDO also might not be a good option. Please let me know what should I do?

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  • \$\begingroup\$ my guess would be that you have/had a break in the audio ground conductor and the USB connection was somehow fixing that. (possibly there was a short-circuit accross that B0505S module) \$\endgroup\$ – Jasen Oct 23 '18 at 4:50
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After I provided a separate power supply through a separate onboard DC DC isolator the noise went away. Earlier I was trying to power the bluetooth module from the 3.3v voltage regulator of Teensy which was creating the noise problem. So bluetooth modules need a ground isolated power supply independently. Even if one takes a isolated power and send it through a voltage regulator of an arduino it will create problems. So a separate DC DC isolator is needed.

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