: Users can tailor the sound to their specific headphones by swapping internal cards. Common cards include: Balanced Card : Best for spacious, 3D soundstages.

: Utilizes two ES9018 chips (one per channel) to achieve high detail separation and a wider soundstage.

: Later versions like the HM-901S upgraded from the original's plastic casing to a more durable CNC aluminum alloy for better heat dissipation. Comparison: HM-901 vs. HM-901S CNC Aluminum Alloy ~3 seconds ("Instant On") DSD Support DSD Support Native Support Volume Control Stepped Attenuator Volume Control Improved Stepped Potentiometer

: Some retailers or direct listings might offer "New" or "Open Box" units of successors like the HM-901S for approximately $1,499 .

: Prices for used units often range from $850 to $885 , depending on the condition and included amplifier cards. Sites like eBay are primary sources for these listings.

: Designed specifically for sensitive in-ear monitors with lower noise floors.

: Features a full-size SD card slot supporting up to 256GB and uses the TAICHI UI with a physical scroll wheel for navigation.