stuartk
The Jay's CD transports do have an excellent OCXO clockl, their transports are excellent in my experience. The Jay's CD transports have 4 different connections: RCA unbalanced SPDIF, BNC unbalanced SPDIF, AES/EBU balanced connections, and of course I2S.
In all of those connections, the digital data and the clock are sent by the transport; and the DAC will use the transport's clock data.
Using the unbalanced RCA/BNC SPDIF connections, the Jay's will transmit the digital data and the clock packed together, in an unbalanced format, and the DAC will then unpack the data and clock, convert back to I2S, and then perform the digital to analog conversion. Some higher end DACs may have the ability to regenerate the clock signal.
The AES/EBU connection will transport the data and clock together, in a balanced format (balanced will do a better job of ensuring the data arrives correctly). That said, the DAC will still unpack the data and clock, convert to I2S, and then convert the digital data to analog.
The I2S connection will transport the data and clock separately, so no need for the DAC to unpack it from the data, and no need to convert to I2S for the DAC, and then the DAC will convert the digital data to analog.
In my opinion (and through some experience), I would use the I2S connection if possible, the AES/EBU if I2S is not available, and the SDIF connections as a last option.