Pros: Luscious sound, UI that's easy to use, sensible price
Cons: Tiny internal storage, UI features primitive graphics, troublesome headphone jack
I've been listening to my iBasso DX90 for several weeks and I'm extremely impressed by its sound, its ease of use and its firmware updates that are more than just cosmetic improvements. While I was deciding whether or not to purchase the iBasso DX90, I spent quite some time comparing it to the FiiO X5 and the wallet-busting Astrell & Kern AK240. In another life, when I return as a billionaire playboy, I will purchase the AK240 or its upgrade so the choice was effectively between the DX90 and the X5. My comparison eventually centered on the iBasso DX90's use of dual Sabre ES9018K2M DACs. I was also swayed by the DX90's apparently superior handling of micro SD cards in comparison to the FiiO DAP, which some reviews of the X5 have criticized as being problematic when using cards larger than 32GB.
The DX90's sound can only be described as luscious and rich. The dual Sabre DACs produce a fullness and an elegance to music that makes lengthy listening sessions a pleasure if not an addiction. Owners of Sennheiser's audiophile grade HD650 headphones will recognize this comparison: the sound of the DX90 is the DAP equivalent of listening to music through a pair of 650s. There is a similar rich sound quality.
Using the UI is simple and intuitive with just enough menu choices to make finding music easy and fast, though the display graphics are antiquated and primitive. One UI attribute I've found particularly helpful is the "directory" menu selection. which calls up all of the nested music choices in an easy to manipulate manner, breaking them down logically rather than in the hodge-podge mess you usually get. If you transfer a lot of music files from a box set, you will appreciate this feature's logical and intelligent presentation. The latest firmware update added several menu choices, The addition of a charge-only USB selection, added to the previous Storage and DAC choices, keeps all of the DX90's operations nicely compartmentalized. Gapless playback really is gapless, Play Modes are simple to manipulate. Music information is easy to call-up and fairly exhaustive.
High resolution playback of up to 24/192 has been error-free except for one album which proved troublesome, causing the DAP to hang after a selection was played. I have reason to believe that the error lays in the album's hi-res encoding and not the player. I haven't been able to reproduce the problem with any other hi-res files. The DX90 plays FLAC, APE, MP3 and WAV files with equal facility. I've found no difference in performance. I haven't tried DSD or DSF files yet, though the twin Sabre DACs appear capable of playing them. However, DSD files are not listed as playable so failure won't be unexpected.
One slightly annoying hardware problem that's cropped up is the headphone jack's selectivity when choosing which 3.5mm audio plug to accept and which to reject as being ever-so-slightly too wide. It becomes necessary to force the plug into the jack when this happens, something that makes me very uncomfortable. A couple of my portable headphones produce only a watered-down mono sound as a result of their rejection by the DX90. Since I own several pairs of portable headphones this is not a serious problem at the moment.
Charging the DX90 takes about three hours when using an AC converter, six hours in a powered USB slot. The DX90 is a bit of a battery hog, with around 7-8 hours of usage at standard resolution and volume, 6-7 hours while playing high-resolution files at higher volume. There is a rudimentary EQ included which lowers the volume when in use so compensation will be required. I tend to avoid using EQ unless absolutely necessary. There are several other features, all of which I found simple and intuitive to use. I've been using 128GB microSD cards, which are necessary since the DX90 only has about 5GB of internal storage. This was an obvious trade-off to keep the price down.
The DX90 is a superb sounding DAC, a great value at its sensible price point and quite easy to use. If you're searching for a reasonably priced DAP capable of playing high resolution music I think the DX90 is an excellent choice.