Krell preamp / Parasound amp power up issue

Hello everyone,

I recently purchased a Krell S-1000 preamp which sounds amazing when mated to my Parasound A51 amplifier. I'm having a few issues with the system, though. Here's what happens:
1. I power up the Krell, it triggers the Parasound with a short delay
2. Just as the Parasound is powering up, there appears to be some sort of spike/short, a low level thump will come out of the speakers
3. As this spike/ground loop/thump occurs, the Krell preamp will shut down,in turn powering off the Parasound because the trigger turns off

If I power up the Parasound first, there isn't an issue. Also, this doesn't happen every time I turn on the system, only sometimes. There's a ground lift switch on the back of the Parasound, I've tried both 'lifted' and 'grounded', get the issue on both settings. Also doesn't seem to occur when I use RCA cables, but there's less hum on the XLR connections and they sound considerably better, so I want to stick with the XLR connections.

I upgraded from an Integra DHC-80.2 also connected with XLR and it didn't have this problem.

My next plan is to try a two prong plug on the parasound. Anyone else have other ideas?

Thanks!
Chris