Glad you have narrowed down the problem DL.
I did mention your issue to a friend and he mentioned it might be a 'cold joint'. He didn't have time to explain to me what that was so I've no idea if that makes any sense or not. Something to do with solder. You will doubtless know what he means.
I've had no issues so far- just sweet sound. Today I'm using the power combo 6BL7/6SN7 with Brimar 6N7GT's as drivers -and the richness of detail and weight of the sound is something I've not experienced before from headphones. Very room speaker-like sound. I know it's always possible to cause damage by injudicious use of tubes but it's so hard to imagine that could be happening when Elise is producing such lovely, effortless sound. I know it can though.
On another point I'm quite concerned about the time it's taking for FA to respond to you.
I emailed about the same time as you with a technical question about Expressivo and have had no acknowledgement. Usually they response very quickly.
I do hope all is well with FA. Maybe an email/ internet glitch over in Poland.
Great, can you send a photo of that setup and how would you describe its' sonic attributes? thanks