Which of the following is NOT a clock source available for the S6000?

The correct answer highlights that USB is not a recognized clock source for the TC Electronic System 6000. The S6000 relies on specific standard clock sources to synchronize audio processing effectively. Internal clock ensures that the system operates at its designated sample rates without needing external references. External Word Clock provides synchronization with other digital audio devices in a studio setup, ensuring common timing. AES/EBU is another prevalent format used in professional audio for transmitting digital audio and also serves as a clock source due to its inherent timing information.

USB, while it might be used for data transfer or communication with a computer, does not serve as a clock source in the context of audio synchronization for the S6000. This makes it distinct from the other options, which are all focused on providing a reliable timing reference for audio processing. Understanding the role of these various clock sources is critical for effective operation of the S6000 in multi-device environments.