After running-in my new cables for UM IEM 12 drivers, i made some comparisons on my 901S (re-cased)
1. the modded 901S has the wordings "Upgraded from HM901" on the display glass.
2. the high low switch is retained where the new 901S does not have the high low switch.
3. tested with 1. RE600, 2: UM 12 drivers, 3. Audeze LCD 3
4. compared with the 901S, AK 240 Gold and Old 901
1. Sound: 901S vs 901
First impression is different soundeing
All headsets tested.
a. RE600, 901S is brighter in the 6k-8Khz. Bass has lesser punch. Maybe because of the brighter sound, the detailing is better.
the bad side for my personal preference, i feel tired after listening to 901S after an hour.
b. Audeze LCD3 The ambience is missing, the 3 dimensional sound from original sound is missing. Listening to Overture 1812, the bass, drums and Canons lacks punch. Detailing is good.
c. UM12, clarity, bass is strong, smooth in both 901 - like the clarity. After listening to female vocals, Cai Qin, Celine Dion and other vocals, they are sweet...male vocals sounded weak.
Overall, i prefer the older sounding 901.
versus AK240:
1. Ak240 has this signature sound of right up in your face with nice imagining. seems like the new 901S is missing that although the detailing is better than the old 901. i am not sure why.
2. 901S amp: Power to drive the LCD 3 is adequate compared to the AK240. Both in Balanced mode.
3. Imaging, AK sounded better marginally.
i have to say, the 901S sounded very nice in the RE600. The Audeze and UM on 901 is better than on the 901S.
Overall feel of the 901S design is still crappy. you need to remove two screws before you can change the battery and the amplifier card.
the look is like some form of poorly design aluminium sheet metal.
Although more modern look now, it is still very retro and feel huge in the palm.
More details if i have the time to listen more music before posting.