For AM3D，Engineer designed 2 sets of THX AAA-78 amplifier modules for balanced circuit.Thank you for the prompt reply @Kean FiiO! The fact it's built on the AM3B rather than the AM3A is great news since the AM3B seems to have meaningfully more power than the AM3A. Like I said, I will probably end up getting the AM3D anyway at some point, but more power is good news for me since I'll primarily be using this to drive MrSpeakers planars.
Speaking of the AM3D THX module, is there any chance you have room to add a 2.5mm balanced connector in addition to the 4.4mm balanced connector (so it would end up having 3.5mm, 2.5mm, and 4.4mm - just like the AM3E)? I know FiiO offers the BL44 adapter to use 2.5mm headphones with a 4.4mm jack, but having the 2.5mm jack built in would be nice for when I'm using IEMs. If it's not physically possible I'll just buy the BL44 - but I figured it was worth asking since we were already talking about connectors
So， it is very difficult to add 2.5mm jack inside.
BTW, 4.4mm become more and more popular than 2.5mm？