Arturia MiniFuse 4 vs SSL 2 Plus MkII

Short answer

More power: the SSL 2 Plus MkII, with 374 mW into 32 Ω; the Arturia MiniFuse 4 has 139 mW. The SSL 2 Plus MkII drives 3 headphones to 100 dB that the Arturia MiniFuse 4 cannot (Moondrop COSMO, Symphonium Crimson, Symphonium Helios).
Hiss with sensitive IEMs: cannot be compared — neither maker publishes a noise figure.
Output impedance: 495 headphones are left alone by the SSL 2 Plus MkII under the one-eighth rule but coloured by the Arturia MiniFuse 4 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 492 more).
Price: the same, $299.

Both are audio interfaces, both at $299.

The SSL 2 Plus MkII reaches 100 dB on 565 of the 567 models here, the Arturia MiniFuse 4 on 562.

Every published figure, next to each other

Specification	Arturia MiniFuse 4	SSL 2 Plus MkII
Power into 32Ω	139 mW	374 mW
Power into 150Ω	45 mW	80 mW
Power into 300Ω	24 mW	40 mW
Power into 600Ω	12 mW	20 mW
Output impedance	10 Ω	1 Ω
Output noise	not published	not published
Price	$299	$299
Headphones it reaches 100 dB on out of 567	562	565

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

Where each power figure comes from

Load	Arturia MiniFuse 4	SSL 2 Plus MkII
32 Ω	Derived	Upper bound
150 Ω	Derived	Upper bound
300 Ω	Derived	Upper bound
600 Ω	Derived	Upper bound

Neither column is a power rating, and the two are not even weak in the same way. The SSL 2 Plus MkII figures are ceilings worked out from a maximum output voltage, on the assumption that the amplifier holds it into the load. The Arturia MiniFuse 4 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 SSL 2 Plus MkII is the one to doubt.

What the labels mean.

The headphones that tell them apart

3 headphones reach 100 dB on the SSL 2 Plus MkII but not on the Arturia MiniFuse 4 — Moondrop COSMO, Symphonium Crimson, Symphonium Helios.

495 headphones are left alone by the SSL 2 Plus MkII under the one-eighth rule but coloured by the Arturia MiniFuse 4 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 492 more).

562 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 HiFiMAN HE400se: SSL 2 Plus MkII has +16 dB of headroom there against +11 dB. 4 dB is about 2.7 times the power, which matters for peaks rather than for how loud the music sits.

The hiss columns are empty for Arturia MiniFuse 4 and SSL 2 Plus MkII because neither maker publishes no output noise figure.

Headphone	Impedance	Needs	Arturia MiniFuse 4 headroom	SSL 2 Plus MkII headroom	Arturia MiniFuse 4 hiss	SSL 2 Plus MkII hiss
Shure SE846	9 Ω	0.04 mW	+30 dB damping	+34 dB	not published	not published
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+10 dB damping	+14 dB	not published	not published
Audeze LCD-2 Classic	70 Ω	0.79 mW	+20 dB damping	+23 dB	not published	not published
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+17 dB	+19 dB	not published	not published
HiFiMAN HE400se	25 Ω	7.9 mW	+11 dB damping	+16 dB	not published	not published
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+10 dB	+12 dB	not published	not published
Sennheiser HD 600	300 Ω	6.6 mW	+6 dB	+8 dB	not published	not published
HiFiMAN Susvara	60 Ω	50 mW	+2 dB damping	+6 dB	not published	not published

The gap in dollars, against the gap in numbers

These two cost the same, $299, so price settles nothing. Out of the 567 models here, the SSL 2 Plus MkII drives 3 models to 100 dB and leaves 495 alone under the one-eighth rule — and on the other side there is no such advantage at all.

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