Still no time...sorry (just finished the water filter replacement from under the sink, also finished the C3X testing and starting the C3R testing today), but I do hope in couple I'll test the FUN again in couple of days.
However, FUN is completely isolated from mains Earth, so the only ground "it sees" would be the audio ground coming from your audio source or output amplifier. I wonder if you could use a multimeter and measure the voltage drop between between audio source's ground and amplifier's ground (measured between RCA outer ground, but also between outer metallic cases). Also, what would be the exact audio source and power amp you're using?
