Interesting. I bought my Lyr used and never experienced the low level hum. I emailed Jason to see if it had the relay and it did not. Off to Schiit to get the relay installed as I like to have the phones plugged in all the time. When I got it back, no difference really.
Anyway, really enjoying the Bifrost/Lyr HD700 combo.
On another note, just picked up the Audinst HUD-MX2. It's surprisingly good with the HD700 and beats any other entry level combo I've had. Going back and forth between the Schiit stack and Audinst, I'm consistently impressed at how well it drives the HD700 and how good it sounds. Very smooth treble with a little roll off, good soundstage and drive. It's not the Schiit stack but I'm really pleased with it. It also works quite well with my iPad Mini (with the a/c adaptor plugged in). If anyone is looking for a second setup on the cheap, I'd highly recommend it.