m903

About the m903

The Grace Design m903 is a high-end stereo reference headphone amplifier and monitoring controller housed in a sleek 1U half-rack enclosure. It features balanced and unbalanced analog inputs, multiple digital inputs including AES3, S/PDIF, TOSlink, and USB with asynchronous transfer mode for bit-perfect playback up to 24-bit/192kHz. The amplifier uses a high-current transimpedance output stage capable of driving low impedance headphones effortlessly. It offers precision level control with 0.5dB steps over a 99.5dB range and channel matching accuracy of 0.05dB. The m903 includes features such as mono mode, crossfeed circuitry to simulate loudspeaker listening, and s-Lock phase lock loop for ultra-low jitter digital stability. The unit has balanced and unbalanced variable level analog line outputs, sealed gold contact relays for signal switching, and an internal linear power supply with a custom toroidal transformer. It supports driverless operation on Mac and Windows up to 96kHz/24bit and requires drivers for 192kHz operation on Windows. The front panel provides intuitive input selection and volume control, with a large white LED display. An optional infrared remote control is available. The m903 is designed for audiophile-quality sound and professional monitoring applications.