Hi all -- I had to gut an antique tube radio I was restoring when the transformer fizzled, so I bought a cheapo bluetooth amplifier module and speakers for the old radio's renewed cabinet. Unfortunately the module does not include an integrated volume control. Using only my bluetooth transmitter (ie. phone) volume control doesn't give me the range I need so I'd like to add a volume pot.

I have only rudimentary knowledge of these things but understand I need to find the bluetooth's output to the amp components, and that's where the volume will need to go. Problem is that I have been so far unable to find a circuit diagram, pinout or any chip info for the module I have. The seller told me nothing was available.

Here's the module: https://www.aliexpress.com/item/Blu...nce-Car-wheelbarrow-Unicycle/32750584986.html

Attached are more detailed pictures of the module, front and back.



I know this is minimal information but I'm grateful for any advice on where I ought to try connecting a volume pot.

Dave

 

If I'm seeing it correctly, you have HT6872 power amplifiers, one for each channel. The gain is controllable by an input resistor value. See this and others:

http://diycarmaint.blogspot.com/2017/09/worlds-smallest-audio-amplifier-class-d.html?m=1

 

The signal comes in across the pot. The output from the wiper goes to IN on the amplifier.

Since this is a stereo amplifier, you will need two ganged pots, i.e. two pots controlled by one knob.

Two different style terminals are shown below. The one on the right is meant for PCB mount. You want the one on the left with solder lug connections.

Channel 1
1 - GND
2 - OUTPUT to AMP
3 - INPUT from SOURCE

Channel 2
4 - GND
5 - OUTPUT to AMP
6 - INPUT from SOURCE