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first of all: noob disclaimer: sorry for the unprofessional sketch and my limited understanding of what I'm doing. I'll try my best to make myself understandable.

I'm trying to make a radio receiver that uses an external audio amplifier, but when I try to use the same power source (the AC-DC adapter), either the DC-DC buck converter or the FM receiver blows out because of over voltage or over current (smoke and sparks effect). Luckily those asian modules are cheap..

But if I use different AC-DC adapters for the FM receiver and the amplifier everything works. Why? How could I use a single power source for powering everything? I suspect the problem is some kind of ground loop etc, but I can't understand how to fix this.

In the below image the AND-gate is supposed to be a 3.5 mm audio jack and not an AND-gate.

schematic

simulate this circuit – Schematic created using CircuitLab

ComponentFryer
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    `those asian modules are cheap` might be the problem ... do you actually have everything connected as per the block diagram? ... measure the voltage between FM receiver GND and audio amp GND – jsotola Mar 01 '21 at 07:30
  • … measure that difference *before* connecting your 3.5mm plug. – Marcus Müller Mar 01 '21 at 08:27
  • Yes I have. I get a feeling my problem relates to this [https://electronics.stackexchange.com/questions/17379/ground-loop-switch-mode-power-supply-noise?rq=1] And per Marcus's suggestion the problems begin when connecting the 3.5 mm plug to the amp. – ComponentFryer Mar 01 '21 at 08:45
  • measure the voltage between the sleeve terminals of both 3.5mm jacks before connecting them. (don't connect them, just measure) – Jasen Слава Україні Mar 01 '21 at 09:14
  • I was fast enough to discard the blown fm receiver so I don't have it anymore, but I took a measure between the buck converters out (-) and the sleeve of the audio input (-) at the amp and the voltage difference was 2.65 V when the buck converter is set to an output voltage of 5.04 V. – ComponentFryer Mar 01 '21 at 15:39
  • According to your diagram you need 5V for the receiver and 19V for the amplifier. If that is correct, then you need the buck converter to make 5V, no question. – Aaron Mar 01 '21 at 18:21
  • Yes that is correct. The receiver takes 5V and the amp can take up to 24V and I'm using a laptop power adapter that outputs 19V. – ComponentFryer Mar 02 '21 at 11:15

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