Need Help with reducing noise of my boombox

[suyashpaliwal]

Hi,

I have made a diy boombox and have connected a Bluetooth module with it but, whenever I switch it on or play any music I get a lot of humming noise and the time I disconnect the speaker from my phone which is connected via Bluetooth the humming noise goes away. I just need help in reducing this noise.
Parts I have used:
1. Transformer 12-0-12 3amps. This transformer : 12V - 3Amp Transformer (230V to 12V) [Heavy Duty] : Online Electronic Components Shop, Price in India : electroncomponents.com
2. 60w 2.1 amplifier. : https://www.aliexpress.com/item/Amp...-finished-board-foot-gun-60W/32665280570.html
3. I am using a buck step down convertor to connect the Bluetooth module with aux input.
4. Power input of buck step down convertor is from one of the DC outlet provided in the amplifier itself.

 

[picowallspeaker]

Hi, I looked at the aliexpress site and the 2.1 module has AC-0V-AC input for the windings of the transformer ( 0V is from the joint of the 2&3 terminals of the two secondaries ) and the Left-Right-subwoofer outputs.
I guess the BT module accepts 6-12 V
You can take +12V ( 15 V) from the positive rail and 0V is ground.
An old 7805 or any kind of linear regulator would do for the purpose of reducing and regulating the voltage for the BT module.
A zener regulator can be used, being just easy and doing its job.

BTW I see the pic again and the supply of the IC is with two zeners...

 

[picowallspeaker]

An old 7805 or any kind of linear regulator would do for the purpose of reducing and regulating the voltage for the BT module.

Skip this if the BT module has its own voltage reg on board.
But generally voltage regs. need to have Vin>Vout of about 3 V .
Nowadays LDO regs. ( low dropout ) are quite diffused, thou...

Otherwise, a simple resistor ( without the zener ) would do "the trick" .
For noise suppression, a L- C cell might be useful

But, in general, bad noise from first powering of various circuits dedicated to audio means problems with ground connections or noise coming from ground returns, oscillations etc...