I have recently tested a Bluetooth receiver with audio output with a pair of amplifiers and different power supplies, but it continues to emit a loud buzzing and noise that covers any audio track. I have seen that there are many people with this problem and also many solutions to this ground loop, but in my case the problem occurs even using two separate power supplies and even disconnecting the BT completely from the amplifier: even connecting only GND and VCC to the receiver and observing the R or L output on the oscilloscope the same audible noise is present, yet it is not connected to anything!
Is it possible that it is a defective model? As you can see from the image, there is also an unsoldered pin of the IC, where the pad is completely missing.
Is it possible that it is a defective model? As you can see from the image, there is also an unsoldered pin of the IC, where the pad is completely missing.
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If there is buzzing with no connection all, that would suggest the BT board is acting as a radio transmitter, and your amplifiers are acting as receivers. The BT board might be at fault, or maybe the amplifiers, or maybe both. Does the buzzing get softer and or go away if you move the BT Board and the amplifiers farther away from each other?
Even with amplification disconnected from every single jumper, including power supply, the noise and buzzing are still present.
Does moving the BT Board away stop the amplifiers from buzzing? If so, and if its power is disconnected then it most likely has a battery or a super cap on the board. More complicated things could be going on too, but less likely.
BTW, your pic is pretty useless. It needs to be in focus enough so we can see the PCB traces.
BTW, your pic is pretty useless. It needs to be in focus enough so we can see the PCB traces.
Have you removed the ground wire from the breadboard and moved it away from the amplifier and other sources of interference? In this case, the noise is still visible, even with lights and other electronic devices turned off, excluding the oscilloscope.
So, the buzzing noise has nothing to do with the BT board?
The amplifier always buzzes when powered on, whether there is a BT board in the room or not? Do you mean you think the BT board has damaged the amplifiers?
If so, what does the waveform look like coming out of the amplifier? Is it of the AC line frequency?
The amplifier always buzzes when powered on, whether there is a BT board in the room or not? Do you mean you think the BT board has damaged the amplifiers?
If so, what does the waveform look like coming out of the amplifier? Is it of the AC line frequency?
Maybe I expressed myself badly or the translator is not working properly, but it is the BT board that is not working, the amplifier or speaker work fine, when the circuit is Battery->(GND + VCC)->BT the noise is still present. I will take a screenshot of the waveform and upload it.
Here is the photo of the missing pin in question:
Here is the photo of the missing pin in question:
Was there a trace now hidden by the red arrow that went to the missing pad? If so, does it look like the trace was pulled too? Does it look like the pad was removed with a sharp knife? I can't see it well enough to tell. The pic is too blurry.
So, the BT board has buzzing mixed in with the audio signal when the BT board is powered up? And, you are using a battery for a power supply? Is there any voltage regulator after the battery? If not, what is the battery voltage? If there is a switching regulator anywhere? If using a USB power pack battery, then there is an SMPS involved.