The most effective "patch" for the BT100 is to stop using the dedicated BT100 port and move to the Digital Inputs. This allows you to use modern receivers that far outperform the original hardware.

Since the BT100 port is a dead end, follow these steps for the best audio quality:

the receiver using the USB port on the back of your Cambridge device (it provides enough 5V power for most small receivers).

Here is the definitive guide to alternatives that offer better range, higher fidelity, and modern codec support.

the receiver's Optical Out to the Digital Input 1 or 2 on your DacMagic or Stream Magic.

The Hardware Reality: Why You Can’t Just "Patch" a USB Dongle

Uses a dedicated Qualcomm 5100 series chip for a rock-solid connection. The "Stealth" Budget Option: 1Mii B06Pro

This is widely considered the "audiophile's choice" for legacy Cambridge Audio gear.

Set your Cambridge device to the corresponding Digital Input.

There is currently no community-made firmware patch to enable third-party USB dongles in that specific port.