Devialet AIR driver update

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As far as I know:
- When using USB only the Expert is responsible for the timing. It is pulling the data from the computer.
- When a different input is used at the Expert there are two units making a timing and both needs synchronization to each other. I think this is more difficult than using USB.

It's not that simple, in either case.

For USB audio, all data on the bus are clocked by the USB clock which is not related to the sample rate. The Devialet buffers the received data and clocks out audio samples at a rate determined by an internal clock. Assuming the sender and receiver are using asynchronous mode, the Devialet provides feedback to the sender so that over long periods of time there is no clock drift. This is somewhat similar to what you described second.

USB is a specific example of a more general case which also applies when audio data is sent to the Devialet over a network: the sender and receiver agree on the audio sample rate, the data are sent over a physical layer which has a completely independent clock frequency, and there is some feedback mechanism from the Devialet to the sender to make sure that things run smoothly and the average rate at which the sender produces samples matches the rate at which the receiver (Devialet) consumes them.