Grace Design m903 specifications

Brand : Grace

Reference headphone amplifier, AS converter and preamplifier The m903 is a stereo headphone amplifier, D/A converter incl. USB interface and preamplifier in a 1U housing with half 19" rack width. The m903 enables professional and excellent sounding headphones and stereo monitoring for music, post production and mastering, whether from analog or digital stereo sources, as well as directly from the Mac/PC. However, it can also serve as an excellent reference D / A converter and system preamp in the audiophile / HiFi sector, as well as an excellent headphone amplifier.

General

Connections The m903 offers balanced and unbalanced analog inputs in stereo via XLR and RCA jacks on the back, for both +4dBu and -10dBV analog sources. Two headphones can be operated simultaneously on the front-side parallel-wired 6.3mm stereo jack sockets. In addition, the m903 has two stereo line outputs on the back (balanced & unbalanced) which allow the m903 to be used as a high-end monitor controller. These two line-out pairs are separately adjustable in level. The Grace Design typical "high-current, transimpedance output amplifiers" are optimized to perfectly control even headphones with the lowest impedances. The precise volume controller controls both headphone outputs and line out levels in exact 0.5dB steps within a 95dB range.

Digital sources are connected on the back as AES 3, S/PDIF or Optical inputs via XLR , RCA and Toslink. An ingenious additional feature is the USB input, which ensures a high-quality direct connection to the computer as a digital input source. A front rotary switch selects between analog, digital and USB sources, a 4-LED display shows the detected sample rate of digital sources between 44.1 and 192kHz. A current, high-quality 24bit DAC, with Grace Design 's own s-Lock(™) dual stage PLL (Phase Lock Loop) performs the D/A conversion with amazing tonal results and extremely low jitter.

Special features The m903 also includes the crossfeed circuit, or x-feed, known from its predecessor, which simulates the natural acoustic environment of speaker listening and the effect of the HRTF (Head Related Transfer Functions). This circuit, designed by Dr. Jan Meier, improves stereo imaging and reduces fatigue when listening through headphones.

Compared to the predecessor model m902, some significant tonal improvements have been realized in the m903, these include, among others:

On the Audio Import product page (see link below) you will find the test reports from STEREO (April 2011) as well as HiFi DIGITAL (March 2011) for download.

Manufacturer:Grace Design
Model: m903
Years of construction: from 2011 (predecessor model m902)
Manufactured in: USA
Color: Stainless steel (natural and black)
Weight: 2.2 kg
Original price approx.: € 1900,-

A new USB interface with asynchronous transfer mode for bit-transparent playback without additional jitter due to the interface - driverless operation on Mac up to 24bit/192kHz (Windows computers need drivers for 192kHz operation).

A D/A converter of the very latest generation with a revised analog signal path achieves an even more musical representation, with a dynamic range improved by 10dB.