Hey all.
I am an engineer but audio-noob who started a project to convert my car radio to bluetooth.
I already learned a lot in the process, and have a working prototype. I even removed most of the noise issues by using a galvanic isolated DC DC converter to power the bluetooth module.
I have two different modules. First I tried this one:
AudioB Plus Bluetooth Audio Receiver Module
then i tried this one:
EB8635 EB8645 Bluetooth BT4.0 Audio Board [Type] - ElectroDragon
With both of the boards I have one remaining issue. ~3 seconds after the music is paused, or when a playlist stops playing the module detects there is no audio anymore and does something which results in a popping sound over the speakers.
When I start playback again by pressing the play button I also hear this pop before the music starts. I have no pop on power-up of the module.
Now both of these modules have a mute pin, which supposedly goes to a logic high when there is no audio. This pin could be used to switch off audio before the module does that on its own. But on both different modules this pin remains at 0V all the time.
I also have bought a CSR SPI programming tool, so I can change settings for the bluetooth module, but so far I have not yet found an option that would disable this behavior.
I guess I am looking for either:
1. a solution to change chip settings so that the audio outputs are no longer disabled, removing the popping sounds in the process
2. an electrical way to remove or filter these pops without affecting the audio itself, or tips how to get the mute mechanism working properly
3. suggestions for other bluetooth modules (without amp) that certainly don't have this issue could also be a solution albeit less satisfactory 🙂.
Thanks a lot!
I am an engineer but audio-noob who started a project to convert my car radio to bluetooth.
I already learned a lot in the process, and have a working prototype. I even removed most of the noise issues by using a galvanic isolated DC DC converter to power the bluetooth module.
I have two different modules. First I tried this one:
AudioB Plus Bluetooth Audio Receiver Module
then i tried this one:
EB8635 EB8645 Bluetooth BT4.0 Audio Board [Type] - ElectroDragon
With both of the boards I have one remaining issue. ~3 seconds after the music is paused, or when a playlist stops playing the module detects there is no audio anymore and does something which results in a popping sound over the speakers.
When I start playback again by pressing the play button I also hear this pop before the music starts. I have no pop on power-up of the module.
Now both of these modules have a mute pin, which supposedly goes to a logic high when there is no audio. This pin could be used to switch off audio before the module does that on its own. But on both different modules this pin remains at 0V all the time.
I also have bought a CSR SPI programming tool, so I can change settings for the bluetooth module, but so far I have not yet found an option that would disable this behavior.
I guess I am looking for either:
1. a solution to change chip settings so that the audio outputs are no longer disabled, removing the popping sounds in the process
2. an electrical way to remove or filter these pops without affecting the audio itself, or tips how to get the mute mechanism working properly
3. suggestions for other bluetooth modules (without amp) that certainly don't have this issue could also be a solution albeit less satisfactory 🙂.
Thanks a lot!
All BT ICs save power consumption and Off the DAC if no use.
1) Try to use differential output i.e. L+ and L+, R+ and R-, then POP noise will be much less
2) CSR BT internal DAC is junk, I recommend to switch BT core for I2S output for better external DAC which being always On, hence, no POP noise
1) Try to use differential output i.e. L+ and L+, R+ and R-, then POP noise will be much less
2) CSR BT internal DAC is junk, I recommend to switch BT core for I2S output for better external DAC which being always On, hence, no POP noise
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