Just got a used Amber from original owner, built May 2014. Listened to it most of the day yesterday feeding it with a Bluesound Node2 streamer. Sounds wonderful playing jazz, vocals and string/horn instruments are very fleshed out and present. Had a bit of a panic last night when I switched to some titles and it went completely silent. All sort of thoughts went through my head ranging from buying a (known) defective unit to bad tube, etc., etc. Same titles played back from other my DAC were just fine. This morning it played perfect but again as soon as I switched to another album, no sound. It all of a sudden hit me that maybe it has to do with albums that are MQA processed. More experimentation confirmed that it basically blocks playback of MQA contents. I knew its not an MQA enabled DAC but apparently for some reason it does not even playback MQA contents. My other non-MQA DAC has no trouble playing MQA material fed from the Node2. I'm also a bit surprised with the absence of any ventilation given the three tubes inside the chassis. Has anyone else with an Amber noticed this MQA behavior? Of course, folks using the DAC for CD playback will not run into this issue. Any general input and wisdom from Amber owners would be appreciated, especially diy upgrades, tube choices, etc.