That was one of the amp protection modes with the Ice amp design: there were several protection modes or errors which could trigger the lockdown indicated by various flashing LED's. Several were detection of high DC current on the amp board, overcurrent in the switch mode power supply, and several others. You could release the lockdown with a reset procedure but I don't know if this still works with the new amp design. I'll try to dig it up for you. It's been posted many times in various threads, SC-05/07, SC-09 and all the following generations.
But your symptoms at a specific spot in the same recording, at what I'd call not unreasonable volume settings, is peculiar. For comparison, my normal volume settings after calibration are more like -12 to -4 db! On both the SC-09 Ice amp receiver and the new SC-68. Magnepans are not very efficient, no doubt much less so than your Apogees or M-L's.
Never heard or even seen Apogees but many planar fans seem to like them I used to think these class D amps could drive anything, because a number of Magnepan owners on the MUG forum have & do use Ice amps from a variety of builders, like Wyred4Sound, Gilmore Raptor, etc. However, I don't know how well they work with e-stats. Plus, the amps in the SC-50 & 60 series are not Icepower, they are a chip amp design from International Rectifier. So, I know I'm in un-charted territory with e-stats & these amps. I realize that you took the brunt of the load off the receiver with the McCormack, but the M-L's on the rears still may be too much of a low impedance load even as surrounds. I just don't have a basis of comparison on an all true e-stat speaker setup. All I can tell you is I've never had problems with Magnepans, but I do have the fronts (3.6R's) on an ext amp, with Magnepan surrounds, Magnepan center, and 2 Advent-like bookshelves as rears, all on the receiver and never had a shutdown, from the VSX-49Txi/59txi class A/B receivers to the SC-09 Ice to this SC-68. And I used to run the fronts as Large, so they were trying to reproduce LFE with the subs.
And when I 1st got this SC-68 I wanted to put it thru the torture test so connected the fronts up to it, ran them as Large, and cranked the volume up to as hi as I could stand, pretty darn close to 0 dB on the dial and it handled Dire Straits Brothers in Arms with no problems, including the drum twacks in the 1st song, which I use for transient attack comparisons. It did about the same as my Innersound ESL-300 amp which is 300 wpc 8 ohm / 600 wpc 4 ohm.
do you use 80 hz as your bass mgmt xover or something else lower?
and it's possible that at that specific spot in the music, there's some substantial hi freq transients which result in the M'L's hitting a low impedance dip and that may be causing the receiver amps to draw too much current...triggering the shutdown. I'm guessing...
can you connect up some conventional speakers & try it?
or it really could be defective in some way, hopefully, an auth shop can confirm
keep us posted on how this turns out for you again, sorry to hear about the problems.
Edited by ss9001 - 11/27/12 at 8:25am