I've tested for a couple of hours a single QV2 in my system... Although I like to believe that I have bat ears, I couldn't hear anything different! Maybe it's my dedicated line, maybe it's the Sigmas or maybe I was really tired... I'll be trying again tomorrow.
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Amp: BAT VK-655SE
Pre-amp/Digital: exaSound e32 w UpTone JS-2 Power Supply; SOtM tX-USBultra w UpTone LPS1.2; Apple Mac Mini w UpTone DC Conversion Kit & UpTone JS-2 Power Supply; Squeezelite w Logitech Media Server 7.9.0
Speakers: Triangle Magellan Cello II
Cables: AudioQuest WEL XLR, AudioQuest Everest, AudioQuest Hurricane HC, AudioQuest NRG-1000, AudioQuest Diamond USB
Rack: Solid Tech Hybrid
Tweaks: Omicron Stabilizzatore Armonico & Gold Evolution SE; IsoTek Sigmas GII w Optimum EVO3; Furutech FT-SWS (R) AC Outlet; Synergistic Research Blue Quantum Fuse