Synchronous vs Asynchronous transmission of digital audio

Another friend has just "discovered" the endless hype surrounding asynchronous digital audio transmission.  Once again, I must write a clarification, as follows:

Asynchronous is best if:

1) You are using USB (this usually means isochronous/asynchronous..the DAC clock drives the advance gathering and buffering of USB data packets from the source...so the source clock is irrelevant)

AND/OR

2) The destination is a DAC.

Hardly anyone but me thinks about the cases where you are transferring data from one digital device to another, such as a chain of digital audio processors (as I have) or a digital recorder (we are not supposed to do that anymore, just buy and listen) through which audio is transferred in real time.

In those cases, if you are using SPDIF (which is almost certain for several reasons), synchronous is better, because the data is not altered, and the timing is best corrected at the ultimate DAC endpoint (which should have asynchronous receiver) rather than at every intermediate point.

Nobody talks about this and I find it infuriating that nobody talks about it.  I post one essay after another.

I can measure the difference in distortion levels at the Emotiva DACs when I switch between synchronous and asynchronous.  It is the smallest amount I can measure, distortion increases from 0.0003% to 0.0004% when I switch to Synchronous mode.  That's not ordinary harmonics but some kind of low level grundge, resulting from jitter, which is being removed by the asynchronous receiver, the accumulation of many little spikes mostly below -130dB rising above the noise floor.

The benefits of asynchronous recevers are very small, IMO, and I wonder if they aren't being endlessly touted by corporate fascists primarily to shut out people like me who like to do loudspeaker experimentation, equalization, recording, editing, and other "dangerous" things, that work better with synchronous receivers.

With a digital recorder hooked up to my living room system, I can record unprotected analog sources such as vinyl records.  (The digital recorder will not allow the recording of protected digital streams like streaming audio or from DVD-Audio discs.)    I used to use a Masterlink, which has a synchronous digital receiver, and records exactly the bits sent to it.  The best recording method was to attach the Masterlink to the output of my Lavry AD converter.  Then I would record exactly at the quality level of the Lavry itself, which is very high.  But the Masterlink is incredibly cumbersome to use and CD's must be burned simply to transfer the data to my computer library.  My new Marantz recorder (PMD 580) is far more convenient as I can record audio files up to 2.1G onto flash memory, without having to mess with extraneous details.  Then I just walk the memory chip over to the computer and copy it (I gave up with the dated network archiving system).  But the Marantz slightly lowers the quality of the recordings, it uses ASRC so all the recorded audio is "interpolated" from the original.  In this case, there is no benefit to me, and in fact a slight loss, from the fact that an asynchronous digital receiver is being used.