Studying the effects of external word clocking after 60 passes through A/D and D/A Converter pairs

After seeing and hearing the dogmatic platitude "external word clocking is superior to internal clocking"
-but finding a dearth of empirical data to support this assertion-
I decided to run some tests to determine the cumulative effect of an external clock on a signal after multiple conversions.

In 2007 I set up an experiment to determine what degradation may result from multiple passes through D/A and A/D loops, and posted those results here.

For this new test, I dragged the same converter out of storage that I had used in the previous test,
but for this experiment I cleaned up the studio a bit, using brand new, very short XLR cables patched directly between the I/O of each channel, a new word clock cable, etc.

I ran the original test audio file through 60 generations of conversion using the internal system clock and again through 60 generations slaved to the external word clock.
The external word clock was generated by a temperature stabilized Universal Audio 2192

Below are links to the resulting files, plus a null file with 68dB of added gain to enable the differences to be heard more clearly.
One of the files is clocked internally and the other one is clocked externally.
I have named the files "A" and "B" in order to make this a blind study.

Can you determine which one is which?

Clock A

Clock B

A-B Null +68dB gain

Chuck Zwicky
October 2013

All content ©2013Chuck Zwicky