Setup

Table of contents

  1. Prerequisites
  2. Installing A2DPWB
    1. Upgrading from v1
  3. Step 1: First-Run Setup
  4. Step 2: Assign WinUSB to the Adapter
    1. Using Zadig instead
    2. By hand in Device Manager
  5. Step 3: Find Your Headphones
  6. Firmware (Realtek Adapters)
    1. In the App (Guided Download)
    2. Bluetooth Chip setting
    3. Manual Download
  7. Recommended Adapters

Prerequisites

  • Windows 10 (22H2) / 11 (x64)
  • Dedicated USB Bluetooth adapter (separate from built-in Bluetooth)

A2DPWB assigns the WinUSB driver to the adapter itself. Zadig is not needed any more (it still works, see Using Zadig instead).

Installing A2DPWB

Each release comes in two forms with the same files:

  • Installer (A2DPWB-<version>-win64-setup.exe): installs for the current user without administrator rights, adds a Start menu entry (A2DP Windows Bridge) and an uninstaller, and installs the Microsoft Edge WebView2 Runtime if it is missing (Windows 11 includes it). Updates install themselves from the app (Settings > Updates > Update now)
  • Portable (A2DPWB-<version>-win64-portable.zip): extract anywhere and run a2dpwb.exe. Keep the three programs (a2dpwb.exe, a2dpwb-core.exe, a2dpwb-driver.exe) together. The portable copy only tells you about updates; it needs the WebView2 Runtime installed

Both keep settings, profiles, link keys and firmware in %APPDATA%\A2DPWB, so you can switch between them. Uninstalling leaves that folder in place.

Upgrading from v1

Run the v2 installer over v1. It asks you to close v1 if it is running, then uninstalls v1 and keeps the settings folder: profiles, the pairing with your headphones and the firmware files carry over, and the headphones do not need to be paired again. An adapter that already has WinUSB (from Zadig) keeps it. If Start with Windows was on, it now starts v2.

At its first start v2 copies the v1 settings to %APPDATA%\A2DPWB\backup-v1\ before it reads them.

Step 1: First-Run Setup

Plug in the USB Bluetooth adapter and start A2DPWB. When there is no profile yet, or no adapter has WinUSB, A2DPWB opens Set up A2DPWB, four steps:

  1. Choose the adapter: the USB Bluetooth adapters found. If yours is missing, plug it in and press Refresh
  2. Driver and firmware: Assign WinUSB (see Step 2), and for Realtek adapters the firmware files (see Firmware)
  3. Find your headphones: put them into pairing mode, Scan Devices, choose them, then Create profile (see Step 3)
  4. Test: choose what to send (all PC audio, a virtual device or one app), Connect, and play something on the PC. If you hear it in the headphones, setup is done

Set up later skips the rest; Settings > Run setup opens it again.

Step 2: Assign WinUSB to the Adapter

A2DPWB communicates directly with a USB Bluetooth adapter via WinUSB, the generic USB driver included in Windows. You need a dedicated adapter – your built-in Bluetooth continues to work normally for regular Windows Bluetooth.

  1. Open the Adapter screen (or the setup’s Driver and firmware step)
  2. The adapter’s Driver reads Windows Bluetooth (or Another driver / No driver). Click Assign WinUSB
  3. Read the confirmation and continue: Windows asks for administrator permission (UAC)
  4. The driver now reads WinUSB (used by A2DPWB)

While WinUSB is assigned, Windows’ own Bluetooth no longer sees the adapter: devices paired with Windows through it stop working until the driver is restored. Use your built-in Bluetooth for normal peripherals (keyboard, mouse, etc.), and never assign WinUSB to the PC’s built-in Bluetooth adapter.

Restore driver on the same screen gives the adapter back to Windows: Windows picks its own driver again (normally its Bluetooth driver) and the adapter works with Windows’ Bluetooth. A2DPWB cannot stream through it until WinUSB is assigned again. The uninstaller offers the same: when A2DPWB put adapters on WinUSB, it asks whether to give them back to Windows (one administrator prompt). Updates keep WinUSB, and so does a silent uninstall (/S).

Using Zadig instead

A WinUSB driver installed with Zadig works just as well:

  1. Open Zadig, go to Options > List All Devices
  2. Select your USB Bluetooth adapter from the dropdown
  3. Select WinUSB as the target driver and click Replace Driver

By hand in Device Manager

If the adapter is missing from A2DPWB’s list, a button on the Adapter screen fails, or your adapter behaves differently from others of its kind, Windows’ Device Manager (right-click Start > Device Manager) does the same by hand. Both need administrator rights. Menu names may differ slightly between Windows versions.

Assign WinUSB

  1. Find the adapter: normally under Bluetooth with its own name (for example “TP-Link Bluetooth USB Adapter”), or with a yellow mark when its driver failed to start. View > Devices by connection helps tell it apart from the PC’s built-in Bluetooth, which you must leave alone
  2. Right-click it > Update driver > Browse my computer for drivers > Let me pick from a list of available drivers on my computer
  3. If Windows asks for a device type, choose Universal Serial Bus devices. Clear Show compatible hardware, choose the manufacturer WinUsb Device and the model WinUsb Device, click Next and confirm the warning
  4. The adapter now shows as WinUsb Device under Universal Serial Bus devices. Restart A2DPWB (or open the Adapter screen again): it uses the adapter as with Zadig

Restore the original driver

  1. Under Universal Serial Bus devices, right-click the adapter (WinUsb Device) > Uninstall device. If the WinUSB driver came from Zadig, also tick Attempt to remove the driver for this device, or Windows picks Zadig’s driver again
  2. Unplug the adapter and plug it in again (or Action > Scan for hardware changes). Windows installs its own driver and the adapter appears under Bluetooth
  3. If it shows a yellow mark there instead (its driver failed to start, for example Code 31), the manufacturer’s driver does not work with it: right-click > Update driver > Browse my computer for drivers > Let me pick from a list of available drivers on my computer > Generic Bluetooth Adapter, or assign WinUSB again as above to use it with A2DPWB

Step 3: Find Your Headphones

Scan Devices (in the setup and in the profile editor) finds nearby devices with the USB adapter for about 10 seconds. Put the headphones into pairing mode first. Devices A2DPWB has paired with before are listed as Paired.

If the scan does not find them, enter the Bluetooth address under Manual: and click Use. Typed or pasted addresses are formatted as you go: AA:BB:CC:DD:EE:FF, aa-bb-cc-dd-ee-ff, AABBCCDDEEFF and AA BB CC DD EE FF all become AA:BB:CC:DD:EE:FF.

From Windows Settings (if the headphones were paired with the PC’s built-in Bluetooth):

  1. Open Settings > Bluetooth & devices
  2. Click on your audio device
  3. Click Properties
  4. The Bluetooth address is shown (format: AA:BB:CC:DD:EE:FF)

From the command line (quit A2DPWB first, tray > Exit):

a2dpwb-core.exe --cli --scan

The new profile starts with Auto as the codec and the system audio as the capture source; the defaults give the best sound. See Usage for everything else.

Firmware (Realtek Adapters)

Realtek-based USB Bluetooth adapters (e.g., TP-Link UB500, RTL8761BU dongles) require proprietary firmware to operate. CSR adapters need no firmware. Intel and Broadcom adapters (experimental) may need firmware files of their own: see Recommended Adapters.

In the App (Guided Download)

The Adapter screen (and the setup’s Driver and firmware step) shows the firmware of the adapter: Firmware OK, No firmware files needed, or Firmware not found with the required file names. Use the Open Download Page button to open the linux-firmware/rtl_bt page in your browser, then use Open Config Folder to open the destination folder. Download the required .bin files and place them in the config folder.

A2DPWB detects the adapter’s chipset and shows which firmware files are needed.

Bluetooth Chip setting

The Bluetooth Chip list on the Adapter screen decides whether A2DPWB runs Realtek initialization (firmware upload) on the adapter:

Choice Meaning
Auto (default) Decided from the detected adapter each time A2DPWB starts. A known Realtek adapter gets its chip; any other adapter gets no Realtek initialization
Not Realtek Never run Realtek initialization. Use it for Intel, Broadcom, CSR and other adapters if Auto does not recognize yours
RTL8761BU, RTL8822CU, … That Realtek chip. Needed for a Realtek-based adapter that Auto does not recognize (an OEM product under its own VID:PID). The status line shows whether its .bin files are in the config folder
Custom Uses custom_fw.bin and custom_config.bin from the config folder

Do not choose a Realtek chip or Custom for a non-Realtek adapter: A2DPWB would try to upload Realtek firmware to it, and the adapter may fail to start.

Manual Download

  1. Download the firmware and config .bin files for your chipset from linux-firmware/rtl_bt (e.g., rtl8761bu_fw.bin and rtl8761bu_config.bin)
  2. Place both files in the A2DPWB config folder (%APPDATA%\A2DPWB, also under Settings > Settings folder)

These firmware files are proprietary Realtek binaries distributed via the linux-firmware project. They are not included in this repository. See WHENCE for redistribution terms.

Recommended Adapters

Chipset Example Products Notes
Realtek TP-Link UB500, RTL8761BU Requires firmware download (see above). Best tested
CSR Generic CSR8510 dongles Works out of the box, no firmware needed
Broadcom ASUS BT400 (BCM20702) Experimental. Adapters that report the vendor class FF/01/01 instead of Bluetooth E0/01/01 (BCM20702 OEM dongles) are detected too. Runs on ROM firmware; an optional PatchRAM .hcd (e.g. BCM20702A1-0b05-17cb.hcd) in the config folder is uploaded at startup
Intel Intel 8265 / 9260 / AX200 / AX201 Experimental. In bootloader mode (e.g. after a cold boot) needs the matching ibt-*.sfi + ibt-*.ddc from linux-firmware intel/ in the config folder. AX210 and newer (TLV bootloader) are not supported yet
MediaTek, Qualcomm MT7921/MT7922, QCA61x4 Not supported: need firmware loaders A2DPWB does not have

USB Bluetooth 5.0+ adapters generally work best for high-bitrate codecs like LDAC.

When several adapters have WinUSB, A2DPWB uses the first one it finds. Keep WinUSB on only the adapter you use for A2DPWB.