Bluetooth Version questions

[kittygirl]

So I read all of what I could find with the search on bluetooth. I am trying to add bluetooth to my little amp speaker boxes I have been building. I bought this one here
Bluetooth Music Receiver A2DP Wireless HiFi 3 5mm Stereo Audio Dongle Adapter | eBay

I plugged the audio cable from the BT module directly into the amp. I spliced in a 12v to 5v converter like this

23mm Car Charger DC Voltage Regulator Converter Module 12V to 5V 3A 15W LS4G | eBay

I realize now after reading this forum that I am probably getting the noise problem from the converter not being isolated.

I just ordered a couple of these as suggested by a member

Invalid Request

Now to the actual questions 🙂

I see that the original bluetooth module is Version 1.

Is the sound quality alot better with the newer versions? I am looking at this one in particular

Bluetooth 3 0 Music Receiver A2DP Audio Adapter Wireless for Stereo Speaker HiFi | eBay

Is this a good option? I am just looking for low cost, low to no noise.

Would love peoples opinions.

Thanks so much

 

[lutkeveld]

A higher bluetooth version will only work if both sender and receiver support this version. Bluetooth is backwards compatible, so getting a BT 4.0/apt-x module doesn't hurt since it allows for upgrades in the future. "sure hifi" on ebay has a native 12v BT pcb, so you won't need to step down the voltage. I have the BT2.1 starter module and I haven't had any problems with it so far.

 

[WesleyK]

Yep and also check if your phone supports APT-X. I know some Samsung galaxy phones do, like the S4, but the iPhone for example, doesnt.

 

[xrk971]

I think higher BT versions support higher data rates but will probably not be any musically quieter. Even with the voltage isolated DC-DC converter, there is still a little noise left if I hold my ear up to the speaker. It is never as quiet as a wired connection. To get it super quiet like commercial BT speaker boxes probably requires a custom PCB with BT and amp integrated together and using the balanced inputs to the amp to cancel out common mode noise from the BT.

 

[WesleyK]

Yep the sure bluetooth modules also have this high frequency noise when the music stops. I use a wire wound inductor in the + line of the bluetooth power supply to suppress most of it.

 

[xrk971]

What value of inductor do you use?

 

[WesleyK]

I believe it was a few mH, 3 of 4mH. I just tested the module with a few inductors I had laying around and that one worked best.

 

[lutkeveld]

Can you explain what's the effect of the inductor in the power line? Why does it suppress the hf noise?

 

[linaudio]

Can you explain what's the effect of the inductor in the power line? Why does it suppress the hf noise?

I'm also curious to know how this works...

 

[lutkeveld]

Little bump, still curious to know how the inductor works. I know it could act as a first order lowpass, but that would filter out other signals too. It would also have to be placed in the signal, not the power line.

 

[gmarsh]

I'll assume it filters HF hash generated by the 12V->5V adapter, which almost always have switching regulators inside. That noise can make it into the ground of the bluetooth dongle through the decoupling caps, and from there onto the output.

Be cautious using large value inductors - if they're not damped with a large enough capacitor then changes in current demand can cause large voltage swings and damage stuff.