Band: opinion spread · Dot: weighted average
A clear strength. Reviewers drove 300 Ω Sennheisers, HiFiMAN planars and even notoriously demanding headphones to loud levels from the 4.4 mm balanced output on high gain, and independent measurements show it slightly exceeds FiiO's ratings. The caveats are consistent: the 3.5 mm output has roughly a third of the balanced power, the low and medium gain settings limit output sharply, and the very hardest loads are beyond it. One owner found the 3.5 mm jack weak next to an older player.
“I found the balanced output to be excellent and on high gain I was able to drive my current hardest to drive headphones, the Modhouse Tungsten to deafening levels.”
Pragmatic Audio
“Once you go above 300-350Ω, even high gain will not be enough to properly drive headphones of that ilk.”
Lynn, Headfonics
“With the same headphones, I need to turn the volume up twice as high on the JM21 as on the Hiby R3 Pro 2019!”
hvalle, Head-Fi (owner review, 3.5 mm output)
Measured
Ankramutt Audio measured, on high gain before clipping, 272 mW into 32 Ω from the 3.5 mm output and 766 mW into 32 Ω, 990 mW into 16 Ω and 93 mW into about 300 Ω from the 4.4 mm output — a little above FiiO's ratings of 245 mW and 700 mW into 32 Ω. On low gain the same bench found only about 17 mW (3.5 mm) and 34 mW (4.4 mm) into 32 Ω. AREGINA Tech Review measured output impedance at 1.5 Ω from the 3.5 mm jack and 4.4 Ω from the 4.4 mm jack, against FiiO's stated ceilings of 1 Ω and 1.5 Ω.
vs. listeners — The 'weak 3.5 mm jack' report fits the measurements rather than contradicting them: the single-ended output has about a third of the balanced power, and anything below high gain cuts it much further. Reviewers also disagree on the hardest loads — Pragmatic Audio drove a Modhouse Tungsten loudly, while eCoustics says not to expect it to get the best from one. The measured 4.4 Ω balanced output impedance is higher than FiiO's figure and can change the sound of low-impedance multi-driver IEMs.