Audient iD24 vs MOTU UltraLite-mk5

Short answer

More power: the MOTU UltraLite-mk5, with 471 mW into 32 Ω; the Audient iD24 has 119 mW. The MOTU UltraLite-mk5 drives 5 headphones to 100 dB that the Audient iD24 cannot (Moondrop COSMO, Moondrop PARA, Symphonium Crimson, 2 more).
Hiss with sensitive IEMs: cannot be compared — neither maker publishes a noise figure.
Output impedance: 546 headphones are left alone by the MOTU UltraLite-mk5 under the one-eighth rule but coloured by the Audient iD24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 543 more).
Price: the MOTU UltraLite-mk5 costs $100 more; what that buys on these numbers is set out further down, under What the price difference buys.

Both are audio interfaces, $599 against $699.

The MOTU UltraLite-mk5 reaches 100 dB on 566 of the 567 models here, the Audient iD24 on 561.

Every published figure, next to each other

Specification	Audient iD24	MOTU UltraLite-mk5
Power into 32Ω	119 mW	471 mW
Power into 150Ω	80 mW	100 mW
Power into 300Ω	58 mW	50 mW
Power into 600Ω	52 mW	25 mW
Output impedance	50 Ω	1 Ω
Output noise	not published	not published
Price	$599	$699
Headphones it reaches 100 dB on out of 567	561	566

Not published means the maker leaves it out, so that axis cannot be compared.

Where each power figure comes from

Load	Audient iD24	MOTU UltraLite-mk5
32 Ω	Derived	Upper bound
150 Ω	Derived	Upper bound
300 Ω	Derived	Upper bound
600 Ω	Recomputed	Upper bound

Neither column is a power rating, and the two are not even weak in the same way. The MOTU UltraLite-mk5 figures are ceilings worked out from a maximum output voltage, on the assumption that the amplifier holds it into the load. The Audient iD24 figures are worked out from figures its maker did publish — power at other loads, or the voltage printed beside it. The second method understates; the first flatters. That is the wrong way round for reading the table straight across, so a gap in favour of the MOTU UltraLite-mk5 is the one to doubt.

What the labels mean.

The headphones that tell them apart

5 headphones reach 100 dB on the MOTU UltraLite-mk5 but not on the Audient iD24 — Moondrop COSMO, Moondrop PARA, Symphonium Crimson, 2 more.

546 headphones are left alone by the MOTU UltraLite-mk5 under the one-eighth rule but coloured by the Audient iD24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 543 more).

561 of the 567 models here reach 100 dB on both.

Headroom and hiss on 8 models, both sources

Headroom is at a 100 dB SPL peak.

The widest gap on the list is the Campfire Audio Andromeda 2020: MOTU UltraLite-mk5 has +15 dB of headroom there against +9 dB. 6 dB is about 3.8 times the power, which matters for peaks rather than for how loud the music sits.

The hiss columns are empty for Audient iD24 and MOTU UltraLite-mk5 because neither maker publishes no output noise figure.

Headphone	Impedance	Needs	Audient iD24 headroom	MOTU UltraLite-mk5 headroom	Audient iD24 hiss	MOTU UltraLite-mk5 hiss
Shure SE846	9 Ω	0.04 mW	+29 dB damping	+35 dB	not published	not published
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+9 dB damping	+15 dB	not published	not published
Audeze LCD-2 Classic	70 Ω	0.79 mW	+22 dB damping	+24 dB	not published	not published
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+20 dB damping	+20 dB	not published	not published
HiFiMAN HE400se	25 Ω	7.9 mW	+11 dB damping	+17 dB	not published	not published
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+15 dB	+13 dB	not published	not published
Sennheiser HD 600	300 Ω	6.6 mW	+9 dB damping	+9 dB	not published	not published
HiFiMAN Susvara	60 Ω	50 mW	+5 dB damping	+7 dB	not published	not published

The gap in dollars, against the gap in numbers

The MOTU UltraLite-mk5 costs $100 more than the Audient iD24. Out of the 567 models here, that difference buys 5 more models driven to 100 dB and 546 more models left alone under the one-eighth rule.

Nothing runs the other way: there is no axis here on which the cheaper of the two does better.

Only published figures count here; blank axes are counted separately.