Did anyone experience Audio Prism's Ground Control

Mesh50, I really wanted to demo them. But unlike for you a professional reviewer the Manufacturer does not support demos. There response to me was to purchase them and if I did not think they did anything try to get a refund.
I have bought items on those terms only to have a real hassle getting my money back

I suppose it is easy to paint all manufacturers with the same brush, when you've had a bad experience. I've read many such tales of woe on Audio Asylum and elsewhere. I think both Audio Prism and Music Direct are very reputable companies and Music Direct would happily refund you. Of course, it is your money and your decision.

Another review in Stereo Times.

I actually have the GC's on my amplifier (an AudioPrizm Debut with new OPT's and power supply mods) on my Sony CD/SACD player and my Planet 10 Fonken boxes with EnABL'd Fostex 127 eN drivers installed. The amplifier GC's provided about half as much back side of the wave information retention as the GC's on the speakers. The CD player GC retained the high frequency information as music, rather than the rather harsh, grainy, unmusical edge to sound that the unit came with. Not proselytizing here (much anyway) but I suspect some folks are wondering about uses in other locations and these have been my results. I do also have them in my transformer, stepped, isolated attenuator preamp, but most folks don't have one of these.

Bud