SMSL M400chat_bubble_outlineFrom real comments

Sound quality impresses owners once burned in, offering a natural and spacious presentation. Multiple owners report the M400 sounds poor or small straight out of the box but transforms after days to weeks of burn-in, becoming detailed and open. One user preferred it over a Denafrips Ares II for its natural, uncompressed, spacious character with smooth treble and no sibilance, even using it without a preamp, calling it a potential endgame DAC for most buyers.

The RCA vs XLR frequency roll-off is a widely discussed design quirk. Several commenters note the RCA output rolls off treble around 3kHz while the XLR output stays flat, which one described as feeling like a design flaw rather than intentional voicing. SMSL reportedly confirmed the RCA signal is altered to sound livelier, though this isn't mentioned in the manual. Some mention a possible future capacitor fix kit, and others noted removal of the output buffer raised output impedance, complicating amp matching.

Frequently compared to the Topping D90, with mixed preference. Owners who have both units describe the D90 as more detailed, layered, and dynamic, with a handy auto-on/off feature the M400 lacks, while the M400 is called fuller, warmer, and more satisfying with a larger soundstage. Preference ultimately splits by taste: some choose the M400 for its musicality, others prefer the D90's transparency and convenience, and one user compared it unfavorably to a Chord Mojo.