I swapped out the pair of digital amplifiers for the 5 watt per channel SET tube amplifier. The spike is gone. I don't get it as I am running the amps through the same DSP.
I picked up a second Antique Sound Labs MG SI 15DT. This one does not have the V-Caps I used to upgrade my first one of these amps, but it does have a pair of super Svetlana Winged-C 6550 tubes, don't know what 12ax7s it's running.
I figure I'll put my other ASL amp into the Emerald Physics system, and swap the Svetlanas for the Tung Sols. That amp uses some wonderful Mullard 12ax7s.
I just got my Yamaha M-80 (M stands for Monster I think) back from its tweaking at Vintage Audio. I'm going to tri amp the Emerald Physics EP2.8s, using the tube amp for the mids, the Yamaha for the bass driver, and maybe the Odyssey Khartago for the coincident tweeter/driver.
I ended up leaving the EP2.8s in the living room for the parties, no one put an elbow through any of the carbon fiber drivers. The system sounded just great.
Still a difficult room.