"mc" wrote in message
. ..

Indeed, because of the elimination of EMI with optical, if anything Sony
should be recommending the use of the optical input for critical
adjustments.

I was wondering the same thing. If it's digital, why isn't it absolutely
bit-for-bit identical both ways? The optical input would be immune to
electromagnetic noise, and that should be the only difference. Normally
they should be indistinguishable because electromagnetic noise strong
enough to disrupt a digital signal is rare.

I was thinking - and someone else pointed out - that it may simply have to
do with their testing logic. There may be some small part of the circuitry
that they want to include or omit from the test procedure at this step.