Actually what I said was, "I gave it 250 hours of un-monitored burn-in, but it sounded fine right out of the box." I didn't say it was better than D2 out of the box, but it didn't sound bad before burn-in. Unfortunately because I just played music 24/7 for over 10 days without listening, I can't say what changed with burn-in or how long it needs, sorry.
And I wrote, "The T3 is not overly bright, nor too forward/too recessed, nor bass-lite - it doesn't seem to do anything wrong, to the point that I may actually prefer the amp section over the iBasso D2 Boa. I'd say it's probably closer to the sound quality of the iBasso D3 or Meier Headsix which is a step up from the D2 Boa. The T3 drops to 2nd tier based on it's detail and transparency vs the top tier amps like Pico, etc, but not based on colorations or frequency response issues." There I said may and probably because I sold the D2 Boa about 1 week before I got the T3, although I had recent memory of the D2 sound and notes about the sound in my big DAC/amp review, and the D3 was sold once I got the D10 long ago.
The D2 Boa had a nice warm sounding lower mids, but it sounded a little thinner in the upper mids, which made it seem a little tipped up in the bass and treble vs the mids. The T3 is a little more level in it's frequency response, so I was able to enjoy it with Grado RS-1 or HD600, despite their different sound signatures. I do feel the T3 has a more intimate soundstage than some other amps, and the D2 Boa's frequency response characteristics help contribute to it's deeper or more distant soundstage. To me, soundstage is not always the most important thing I look for, as I also look at frequency balance, and transparency/detail. The D2/D3 may be more detailed than the T3 (the D4 certainly is) but I don't have them to compare anymore.
I would give it at least 100 hours, but many of the amps I have reviewed didn't fully open up till 250-300 hours, some even longer.
Thank you very much for your quick and in-depth response! I was just a little confused when I read your review. I wanted to know if I should expect changes during the amps break in stage. I will report back once I have 50+ burn in time.