Small breakout board for this tiny BT transmitter, with optional components either SMD or TH
Update! If you use a small antenna like this it will increase the range quite considerably (link below):
Thanks Dave Harris for this heads up!
Suggested circuit diagrams from manufacturer:
Bluetooth Audio Transmitter Module Board 4.1 Stereo Audio GFSK Transceiver Wireless Speaker Headphones KCX_BT_EMITTER 5V
https://s.click.aliexpress.com/e/_9iRqhc
Typical small 2.4GHz antenna with lead and tiny plug suitable for this board:
https://s.click.aliexpress.com/e/_9JXN6r
Anker Bluetooth Speaker I used in the demo, small but sounds OK.
Can play from SD card, AUX in, FM Radio and BlueTooth.
https://amzn.to/320sH9Q
Utilities to help program the KCX_BT_EMITTER by Mark-MD047
https://github.com/Mark-MDO47/BluetoothAudioTransmitter_KCX_BT_EMITTER
Electro-Tech-Online (aka Dr G) with details of AT commands (and more) for the KCX_BT_EMITTER
https://www.electro-tech-online.com/threads/kcx_bt_emitter-low-cost-bluetooth-bt-audio-module.158156/
Partly translated documentation for AT commands
https://www.electro-tech-online.com/attachments/atwithsomeenglish-jpg.122398/
AT Command List for ESP (Espressif)
https://docs.espressif.com/projects/esp-at/en/latest/AT_Command_Set/Basic_AT_Commands.html