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Re: Thomas some answers

Thomas,

You can use the PCM in several ways though kinda of hidden in the data sheet. It can be used ASYNC as well as isosynchronous.

In ISO mode the clock is pretty stable as the USB controllers on the computer side have a large enough buffer as to not conflict with the speed. Therefore the SPDIF could go directly to a SPDIF receiver and out in the format needed for the particular dac chip required. No other clock needs to be applied.

Jitter in this regard is reduced because there is no relationship to the dive mechanism and position of the head which is more of an issue with jitter that I have tested. This is what led me to do a USB dac. When I was working on a secondary PLL for a crystal receiver I was shocked at how much the clock changed in relationship to the position of the head. So too the amount of jitter. That and crappy MCLK's in even expensive transports.

Therefore USB to SPDIF will result in lower Jitter than say transport to DAC directly.

This is also true (at least with iTunes) that when a CD is played it is buffered to the tune of a few buffer lengths of the USB buffer required by the controller.

Have fun,
Gordon
J. Gordon Rankin


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  • Re: Thomas some answers - Gordon Rankin 12:06:06 10/28/04 (0)


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