The HA-2 and HA-2SE portable headphone amplifiers were designed to be compatible with micro USB and Lightning connections. They are not designed with USB-C compatibility in mind, and the varying implementations USB-C technology make support for that connection type unreliable.

Depending on the USB-C device in use, there may be issues with establishing a connection, charging or connection stability. These cannot be addressed by OPPO short of a hardware re-design, which is no longer viable since OPPO Digital shuttered their production line in April 2018.