The Well-Tempered Computer, an introduction to computer audio

Wednesday, January 26, 2011

Grace Design M903

After launching the excellent M902 six years ago, Grace Design's M903 is its new reference headphone amplifier, DAC, and monitor controller.






  • 24bit/192kHz digital stereo inputs- AES, S/PDIF, TOSLINK and USB 
  • A new volume control provides higher headroom and lower distortion and noise
  • Precision level control with a 99.5dB range in 0.5 dB steps 
  • Ultra-low noise balanced I/V current to voltage converter 
  • Asynchronous high speed USB interface which is driverless USB Class 1 operation on Windows and Mac up to 24bit/96kHz and USB Class 2 audio for 24bit/192kHz operation on Windows and Mac (drivers needed for 192kHz operation under Windows)
  • Mono mode for checking mix phase issues (or listening to Pet Sounds)
  • s-Lock™ phase lock loop sample clock regeneration for ultra-low jitter 
  • High-current trans-impedance headphone amplifier circuitry built to effortlessly drive low impedance headphones
  • Balanced and unbalanced analog inputs
  • Balanced and unbalanced variable level analog line outputs (we only unbalanced?)
  • Improved power supply architecture isolates headphone power amplifiers, line amplifiers, DAC's and digital logic 
  • Channel level matching accuracy of 0.05dB
  • Improved x-feed circuit eliminates perceived loss of low frequency content
  • Optional infrared remote control available
  • Internal linear power supply with custom wound toroidal transformer
  • Sealed gold contact relays used for all signal switching
  • Five year transferable warranty on parts and labor