LampizatOr Amber (original version)

Just got a used Amber from original owner, built May 2014, mostly out of curiosity. Listened to it most of the day yesterday for the first time feeding it with a Bluesound Node2 streamer. Sounds wonderful playing jazz, vocals and string/horn instruments are very fleshed out and present with great detail.  Its a hefty full size chassis unit and seems very well built. It has a Sabre DAC chip but is tube rectified (6x5 tube) and has two triode tubes in the output/buffer stage; Ecc81 and Ecc82. 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 tubes, etc., etc. Same titles played back from my other 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. Has anyone else with an Amber noticed this MQA behavior? Not really a big deal for me but interesting behavior nonetheless. 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, general care, etc. Looking at the posts in Audiocircle it looks like most folks go for their higher end models. All in all a great sounding DAC especially given the reasonable used price(s).

P.S. Sent a couple of emails with questions via their website and received responses within minutes. They seem to have a decent customer service. 

There is an "MQA external DAC" toggle switch in the audio settings on the Bluesound - might be worth checking to make sure it's off.
congrats on a great DAC choice :-) like all things tube, rolling can be rewarded for sure. I would start with the  output, Andy at Vintage tube is my go to guy and he has incredible test gear- this DAC also benefits from HRS or other isolation feet and a damper on the sheet metal cover. I would also try to run this on a separate circuit from your preamp/amp as I do with anything digital.
Thank you guys. I don’t see the MQA toggle in Bluesound app but I did try it in Tidal and it made no difference. Not a big deal for me. As for tubes and damper sheet, it has RCA rectifier tube and Brimar output tubes which I think are aftermarket but it already has damper sheets applied under the top cover and bottom chassis plate, apparently OEM according to some pictures I’ve seen. The more I listen to it the more I notice the subtle nuances it’s bringing out, like more decay in vocals and instruments and less metallic glare in cymbals. Nice piece of gear.