FiiO M21sourcefeedsAudio-Technica ATH-R50xheadphones
Used together in 1 real system
Works, with caveats
FiiO M21 + Audio-Technica ATH-R50x works, with a couple of tradeoffs worth knowing before you commit.
What the compatibility check found
Headphone Impedance Matching
Caveat⚠ Poor impedance match (damping factor: 1.6)
Use a headphone amplifier with lower output impedance (typically <1Ω for low-impedance headphones, <10Ω for high-impedance headphones)
Physical Connectivity
Couldn't verifyConnector matching does not apply to this pairing