FiiO K9 AKM

Sources split, and this is the canonical electronics argument in miniature. One camp reports the K9 AKM measures and reads as neutral — that the converter swap is a spec-sheet event, not a sonic one. The other hears a consistent, repeatable character next to the ESS-chipped K9: warmer, rounder, less etched, more forgiving of poor recordings. Notably the two camps agree on the direction of the claimed difference; they disagree only on whether it is real.

Sources split, but along a load boundary rather than a matter of taste. Through about 300 Ω everyone reports abundant headroom — HD 600/650, HD 660S2, FT3, Ananda Nano, HE1000 Stealth all come up as comfortably driven. The reviewers who find it short are all reaching past that: a 600 Ω AKG 240DF, an HE6se v2, a Susvara. That boundary is not a mystery — it is roughly where FiiO's own recommended load range stops.

The widest split in the set, and it is really a disagreement about what you are buying. Reviewers who weigh the whole package — chassis, linear supply, the I/O, Bluetooth, three headphone outputs — call it a lot of hardware for the money and rate it above its siblings. The measurement-minded reply that a far cheaper DAC will measure the same and that the built-in amp is redundant if you already own one. A returning owner adds a third angle: at this price the software polish should be better than a box costing a third as much.

The most consistent praise in the set. Reviewers using very sensitive IEMs report an inaudible floor, and the low output impedance keeps multi-driver IEMs from being tonally skewed. The only recorded caveat is narrow: one reviewer heard a faintly less-than-black background on high gain with a single planar IEM, and none below high gain.

“The background, similar to the K9, is pitch-black.”

Headfonia

“Background noise is inaudible even with very sensitive earphones such as the FiiO FX15.”

Ichos · Head-Fi

Mostly agreement, with a specific and repeated exception. The connector count is the headline — three headphone outputs, RCA and XLR line/pre-out, USB-B plus a side USB-C, coax, optical, and a 4.4 mm balanced line-in that is genuinely rare at the price — alongside Bluetooth 5.1 with LDAC, three gain settings and separate DAC, pre-out and headphone modes. The exception is the app: the parametric EQ works only on the Bluetooth input, and there is no remote and no volume control in the app, which several reviewers name as the one thing keeping it off the top of the class.

“Also, there is a 4.4mm input on the back, a rare feature in this price range.”

Headfonia

“Unfortunately the EQ is only effective in Bluetooth reception mode.”

Ichos · Head-Fi

Consistently praised. A 2.66 kg sandblasted CNC aluminium chassis with an internal linear transformer, gold-plated connectors, an included vertical stand, and a temperature that owners describe as warm rather than hot. The recorded negatives are minor and cosmetic — the matte finish shows fingerprints and the front-panel lettering is small in dim light — with one genuine outlier: an owner on the official thread reported the unit dropping to a red status ring and silence a few weeks in, and referred to other owners hitting the same fault.

“The build quality is exemplary. It is sturdy, durable, and meticulously assembled.”

Headfonia

“This piece has substantial weight, plus the finish quality is exceptional.”

Audio Pursuit

Split by layer rather than by opinion: reviewers like the metal and dislike the software. The volume knob draws some of the strongest praise in the set — 120 steps with no sudden jumps in level — and the switch-and-LED front panel is learned in minutes. Against that sit a set of recurring niggles: no volume readout in a dark room, no remote, a knob some wish were detented, occasional Bluetooth pairing struggles, and settings such as the LED ring that revert on every power cycle. It is a big, heavy unit that takes real desk space unless you stand it up.

“This is one of the smoothest operating volume knobs I have used.”

Headfonics

“Does not remember setting from the app to turn off the RGB. I have to turn it off after every single power cycle.”

u/ExxInferis · r/FiiO