This application relates to transfer of digital audio data between a host device and an accessory apparatus that may be connected to the host device via a suitable connector, such as a USB connector. A path selector is operable to establish either a first digital data path or a second digital data path for transfer of digital data. The first digital data path includes a first data bus host and a general purpose digital data interface suitable for bulk data transfer between the first data bus host and the applications processor of the device. This may be a default USB path. The second digital data path includes a second data bus host and at least one pair of second path data interfaces. The second data bus host does not form part of the applications processor and each of said second path data interfaces comprises a digital audio interface suitable for streaming of audio data. The path selector selectively establishes the first data path for bulk digital data transfer or the second data path for streaming of audio data where latency is important.