Overview

The Solid State Logic SSL 2+ MKII is a 2-in/4-out, 32-bit/192 kHz USB-C audio interface aimed at home and project studios. MKII brings measurable updates over MKI—most notably 120 dB A-wtd dynamic range on the balanced line outputs and lower THD+N—while the 2+ variant retains SSL’s optional Legacy 4K enhancement and, critically, provides two headphone outputs with independent mixes. [1][2][3]

Scientific Validity

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Manufacturer data for MKII specify balanced outputs: 120 dB A-wtd DR, THD+N −108 dB (<0.0004%); mic preamps: 116.5 dB DR, EIN −130.5 dBu; and tight frequency response (≤±0.03–0.05 dB). [1] The 2+ model additionally offers independent headphone mixes without sacrificing those output specs. [2][3] As comprehensive third-party lab measurements for MKII are still limited, we discount for confidence and set 0.7.

Technology Level

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MKII moves to 32-bit/192 kHz conversion with across-the-board spec gains (e.g., outputs 112→120 dB DR vs. MKI) and keeps the user-switchable Legacy 4K circuit for optional coloration. [1][3] The 2+ variant’s dual independent headphone mixes and MIDI I/O align with modern small-studio workflows. [2][3]

Cost-Performance

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Street price (US): 299.99 USD. [4]

To be strictly equivalent, a comparator must simultaneously match the SSL 2+ MKII’s functions—4 analog line outputs, MIDI I/O, and two independent headphone mixes (without consuming the line outputs)—and meet its measured neutrality (≈120 dB-class line-output DR with low THD+N). [1][2][3]

• MOTU M4: has MIDI I/O and 120 dB DR on main outs, but only one headphone output; creating a second independent HP mix requires using outputs 3/4, which then leaves just 2 line outputs available—not simultaneously equivalent to SSL’s 4 line outs + dual HP mixes. [6]

• Cheaper “feature-match” units (e.g., Steinberg UR44C with 6 TRS outs, 2 headphones, MIDI) do not hit 120 dB-class output performance in published figures/retailer specs. [8]

The lowest-cost model we can verify that meets or exceeds both the function set (≥4 line outs and 2 HP outs and MIDI) and offers ≥120 dB-class conversion is Focusrite Scarlett 18i20 (4th Gen) (two independent HP outs, MIDI I/O, 122 dB DR), at 699.99 USD. [9][10] Since no cheaper configuration achieves full equivalence as of 2025-08-16, the SSL 2+ MKII is the cheapest equivalent, so CP = 1.0.

Reliability & Support

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SSL has established distribution, drivers, and documentation; nothing in MKII suggests unusual risk. Model-specific long-term field data remain limited, so we keep this slightly above average.

Rationality of Design Philosophy

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MKII’s revisions emphasize verifiable performance while leaving “4K” as an optional creative effect. The 2+ model’s 4 line outputs, MIDI I/O, and two independent headphone mixes are practical for cueing and external gear without compromising baseline transparency. [1][2][3]

Advice

If you need 4 line outs, MIDI I/O, and two independent headphone mixes in a compact interface—and you care about transparent measurements—the SSL 2+ MKII is a balanced choice with no cheaper fully equivalent alternative right now. If you don’t need dual HP mixes or MIDI, many 2×2 interfaces cost less; but once you add boxes to replicate SSL’s function set and maintain 4 line outs, the total typically exceeds the 2+ MKII.

References

1. SSL Support — “SSL 2/2+ MKII Audio Performance Specifications Compared to MKI” — https://support.solidstatelogic.com/hc/en-gb/articles/21551651147677-SSL-2-2-MKII-Audio-Performance-Specifications-Compared-to-MKI
2. SSL Support — “What’s new with SSL 2+ MKII compared to MK I?” — independent headphone mixes — https://support.solidstatelogic.com/hc/en-gb/articles/22545649456541-What-s-new-with-SSL-2-MKII-compared-to-MK-I
3. SSL Press — “SSL 2 MKII / 2+ MKII Launch” — 120 dB outputs, product overview — https://solidstatelogic.com/media/solid-state-logic-launches-ssl-2-mkii-and-ssl-2-mkii-audio-interfaces
4. Sweetwater — “Solid State Logic SSL 2+ MKII” — 299.99 USD — https://www.sweetwater.com/store/detail/SSL2Pmk2–solid-state-logic-ssl-2-mkii-2-by-4-usb-c-audio-interface
5. 価格.com — “SSL 2+ MKII” — 国内最安例（円）— https://kakaku.com/item/K0001663541/
6. B&H — “MOTU M4 USB-C Audio-MIDI Interface” — specs: 1 headphone out, MIDI I/O, 4×4, DR figures — https://www.bhphotovideo.com/c/product/1514483-REG/motu_3140_m4_4x4_usb_c_audio.html
7. SECONCEPT — “Native Instruments Komplete Audio 6 Mk2” — DR ≈ 105 dB, THD+N ≈ 0.006% — https://seconcept.com/products/komplete-audio-6-mk11
8. Sweetwater — “Steinberg UR44C” — 6 TRS outs, 2× HP, MIDI I/O (function cross-check) — https://www.sweetwater.com/store/detail/UR44C–steinberg-ur44c-usb-audio-interface
9. Focusrite User Guides — “Scarlett 18i20 Specifications (4th Gen)” — two HP outs, extensive line outs — https://userguides.focusrite.com/hc/en-gb/articles/21616107507218-Scarlett-18i20-Specifications
10. B&H — “Focusrite Scarlett 18i20 (4th Gen)” — 122 dB dynamic range, MIDI I/O — https://www.bhphotovideo.com/c/product/1847364-REG/focusrite_scarlett_18i20_4g_scarlett_16i20_usb_c_audio_midi.html

(2025.8.16)