Quick comparison of P90SD and HA300.
P90SD-
Perceived balance: Very slightly warm, yet still unforgiving of bright headphones or bad recordings because it is just brutally detailed. Black background and low impedance.
Bass: Very slight mid bass hump, but as tight as it gets, great impact, sub bass loses to mid bass for ear time as a result.
Mids: Slightly warm, smoother, not as in your face, kinda honeyed yet detailed, mids are in line with treble.
Treble: Slightly warm, excellent timbre, cymbals sound spot on.
Sound stage: Small, but extremely dense texture and timbre, and no artificial walls to the sound, most larger sound stage daps sound thin and lacking body and realism in comparison (Cayin N6...).
HA300-
Perceived balance: Very slightly cold, perceived detail is higher as a result of the slight coldness. Brutally detailed +1. Black background and low impedance.
Bass: Essentially perfectly balanced between sub bass and mid bass, very neutral, sub bass is easier heard due to the neutral balance.
Mids: Slightly cold tonality, aka slight upper mid emphasis, mids as a result seem more upfront, increasing perceived sound stage size, mids are in line with treble.
Treble: Slightly cold tonality, increases sound stage size.
Sound stage: Medium, not as dense in textures, but bigger sound stage in return, no artificial walls to the sound, does not suffer from lacking body.
Bottom line: I can't pick one as the winner, they both sound excellent and I honestly like both equally. For each category of bass mids and treble I found that I prefer presentation of some songs on the P90SD and other songs on the HA300. The differences I'm talking about are small differences, I classify both as very neutral daps that are extremely detailed. For example, I might be describing P90SD as slightly warm (which is what I hear) but I'm a veteran of neutral sound, I guarantee any person on the street would find it bright or bass light, but it's just very detailed and neutral with the perceived tonality that I described above, same for HA300, I descibe it as slightly cold, but it's just extremely detailed and neutral with the perceived tonality described above. I'm very happy to have both daps as its nice to have two slightly different takes that retain balance and detaile. Both daps excel in timing and pacing of the music compared to all other dap's I've heard, and also have blacker backgrounds. It's Interesting to hear what a change in two pairs of opamps for LPF and Voltage Follower did to the sound between the daps. Very cool.
Cheers
/