I have a 990 that will loose all sound in a TV program or even better, will just output the low end. What does it is the detection of a signal change.

To clear it up, I switch Dolby modes, and all is back to normal. It's not just the 997...

Try this as well.

Only turn on the Pre-Amp and Amp.
Put the preamp on an input that does not show the SB speakers as being active. No components turned on.
Turn the volume to -75 then -76.
Turn the Pre-Amp to an input that shows the SB as being active.
Turn the volume to -75 then -76.

Do you hear a ticking coming through the speakers?

I can unplug EVERYTHING from the Preamp and use the jack in the front and still hear a tick when I go from -75 to -76 in the example above.