This thread is a follow up to my earlier thread: https://www.diyaudio.com/community/threads/bluetooth-audio-receiver-possible-solution-for-all-kind-of-noise.384052/
When adding a bluetooth receiver to our speaker builds, we often use a DC-DC converter to step down the supply voltage since we would like the receiver to use the same power source with the amp but without frying it. However, DC-DC converters are actually noisy due to its nature. For more informations on this, you may search for the working principle of a DC-DC buck converter.
Anyway, the root problem of the issue is the dirty power supply to the bluetooth receiver. Just when Im about to give up, I finally figured out how the industry can use a very cheap bluetooth receiver on their class-D amps (the crappy ones with iconic Chinese styled English speech), but still providing a low noise compared to my DIY builds.
If you have a amp board with bluetooth by your hand, you might notice right away that they don't even have DC-DC converter on it. But, you would find something like this near its bluetooth module:
These are voltage regulators, or LDO. If you quick google what is LDO and its advantages, you would know why they are commonly used in these boards. They are cheap, small, require less components, yet offer very clean power source.
The solution is obvious, when the supply voltage is too high for your bluetooth receiver, use a voltage regulator to supply power to your bluetooth receiver. Typically, a LM7805 would do the job for you.
To make the power even cleaner, decoupling capacitors can be used in the circuit. Here I am providing an example of my own PCB design for supplying power to the bluetooth receiver. (Made it into a connector, where the receiver will be connected to get its power.)
PS: Voltage regulators are rated for very low current, they can be hot under normal operation. Therefore I recommend sizing a much larger one in your circuit. (I actually picked one that is rated for 500mA even tho my bluetooth receiver only draws 64mA from the aboves example.)
I hope this helps anyone that is trying to DIY their own bluetooth speakers. Good luck on your builds!
When adding a bluetooth receiver to our speaker builds, we often use a DC-DC converter to step down the supply voltage since we would like the receiver to use the same power source with the amp but without frying it. However, DC-DC converters are actually noisy due to its nature. For more informations on this, you may search for the working principle of a DC-DC buck converter.
Anyway, the root problem of the issue is the dirty power supply to the bluetooth receiver. Just when Im about to give up, I finally figured out how the industry can use a very cheap bluetooth receiver on their class-D amps (the crappy ones with iconic Chinese styled English speech), but still providing a low noise compared to my DIY builds.
If you have a amp board with bluetooth by your hand, you might notice right away that they don't even have DC-DC converter on it. But, you would find something like this near its bluetooth module:
These are voltage regulators, or LDO. If you quick google what is LDO and its advantages, you would know why they are commonly used in these boards. They are cheap, small, require less components, yet offer very clean power source.
The solution is obvious, when the supply voltage is too high for your bluetooth receiver, use a voltage regulator to supply power to your bluetooth receiver. Typically, a LM7805 would do the job for you.
To make the power even cleaner, decoupling capacitors can be used in the circuit. Here I am providing an example of my own PCB design for supplying power to the bluetooth receiver. (Made it into a connector, where the receiver will be connected to get its power.)
PS: Voltage regulators are rated for very low current, they can be hot under normal operation. Therefore I recommend sizing a much larger one in your circuit. (I actually picked one that is rated for 500mA even tho my bluetooth receiver only draws 64mA from the aboves example.)
I hope this helps anyone that is trying to DIY their own bluetooth speakers. Good luck on your builds!