|Grace Design - m903 - Reference Headphone Amplifier / DAC
Refined and Rich Sounding
Ten years ago, Grace Design launched the model 901 headphone amplifier and followed it four years later with the popular m902. How could Grace possibly top the m902? The company's new m903 is a refined and rich-sounding headphone amp with an onboard 24-bit, 192 kHz DAC. A full complement of connections adds to the impressive features list.
"The Grace Design m903 continues the tradition set by its predecessors by being 'a great, high-resolution DAC on a very cost-effective package' that offers remarkable clarity, continuity, and roundness of tone, and is better in almost every way than the m902," notes John Marks in the December 2011 issue of Stereophile magazine.
New Design Ups the Ante
The Grace m903 retains everything that was great about its predecessors, adds some useful new features, and ups the ante with even better audio performance. A new volume control provides higher headroom and lower distortion and noise. New generation DACs and an ultra-low noise, balanced current-to-voltage converter yield even more musical performance compared to the m902. The improved s-lock PLL circuitry delivers lower phase noise and jitter. An improved power supply isolates headphone amplifiers, line amplifiers, DACs, and digital logic, resulting in lower noise and distortion.
All New-High Speed USB Interface
Perhaps the most exciting improvement is the all new high speed USB interface. This cutting edge technology provides a completely asynchronous data transfer mode, which allows for bit-perfect USB playback with zero interface-induced jitter. This new interface affords standard driverless USB 'Class 1' operation on Windows and Mac up to 24-bit, 96 kHz and USB 'Class 2' audio for 24-bit, 192 kHz operation on Windows and Mac (drivers are needed for 192 kHz operation under Windows). This is computer-based audiophile playback that will satisfy the most diehard purist.
New crossfeed circuitry is even more useful and includes a gentle compensation to eliminate the perceived loss of low frequency content. Both balanced and unbalanced line outputs are now standard, with individual volume controls for each. Grace Design has even included a mono mode for checking a mix for phase issues or simply monitoring in mono (or listening to Pet Sounds). These improvements cement the m903 as the perfect compact, audiophile-grade monitor controller, even for larger scale production environments with more than one set on monitors.
A Full Complement of Connections
Oodles of connectivity extend the capability of this superb component. A full complement of analog and digital inputs are provided: balanced, unbalanced, AES3, S/PDIF, Toslink, and USB. They are user-selectable via a precision rotary front panel switch. Grace also offers an updated optional infrared remote control, which provides essential control for anyone working 'out of reach' of the m903.
- Balanced and unbalanced analog inputs
- 24-bit, 192 kHz digital stereo inputs- AES3, S/PDIF, Toslink, and USB
- High-speed USB interface with completely asynchronous transfer mode
- Driverless operation on Windows & Mac up to 96 kHz, 24-bit
- Supports USB 'Class 2 audio' specification for 192 kHz, 24-bit operation on Windows and Mac (drivers needed for 192kHz operation under Windows)
- New generation DAC's and ultra low noise balanced current to voltage converter
- Mono mode for checking mix phase issues (or listening to Pet Sounds)
- s-Lock phase lock loop sample clock regeneration for ultra-low jitter and rock solid digital stability
- High-current transimpedance headphone amplifier circuitry built to effortlessly drive low impedance headphones
- Balanced and unbalanced variable level analog line outputs
- Improved power supply architecture isolates headphone power amplifiers, line amplifiers, DAC's, and digital logic
- Precision level control with a 99.5 dB range in 0.5 dB steps
- Channel level matching accuracy of 0.05 dB
- 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 manufacturer's warranty on parts and labor
- Gain: Headphone output, volume at max, trim at +9.5
+15 dB; Balanced Line output, volume at max, trim at +9.5
+14 dB; Unbalanced Line output, volume at max, trim at +9.5 +11 dB
- Frequency Response: @ 0 dBu out +/- .25 dB, 22 Hz 120 kHz; @ 0 dBu out +/- .5 dB, 12 Hz 260 kHz; @ 0 dBu out +/-3 dB, 4Hz 600 kHz
- Maximum Input Level: Balanced Input, +22 dBu; Unbalanced Input, +22 dBu
- Maximum Output Level, Unbalanced output @1 kHz, 100k Ohm, +22.5 dBu; Balanced output @1kHz, 100 k Ohm,
+27 dBu; Headphone output @1kHz, 50 Ohm load, 20.4dBu
- Impedance: Balanced Input, 106K Ohms; Unbalanced Input, 53K Ohms; Balanced Output, 95 Ohms; Unbalanced Output, 47.5 Ohms; Headphone Output, 1.2 Ohm
- Dynamic Range: @ 0 dB gain, TBD; @ -10 dB gain, TBD
THD+N; Headphone +10 dBu out, 50 Ohm load, SMPTE 4:1
<0.01%; Headphone +10 dBu out, 50 Ohm load <0.008%;
Unbalanced Line Out, +10 dBu out, TBA; Balanced Line Out, +10 dBu out, <0.002% Attenuator
- Channel matching: <0.05 dB
- Attenuator Range : 99.5 dB
- Input Sample Rate: 32, 44.1, 48, 88.2, 96, 176.4, 192kHz
- THD+N: 44.1 kHz, 24-bit, 1kHz, +20 dBu out, <0.002%
- Noise Floor: 0 dB gain, 22-22 kHz -94 dBu; 0 dB gain, A-weighted, -97 dBu
- Output level: Unbalanced Output @ 0 dBFS, TBD;
Balanced Output @ 0d BFS, TBD
- Power Requirements: 120 VAC, .16A; 230 VAC
- Dimensions: 8.5" wide, 1.7" high, 8.25" deep
- Weight: 5 lbs
"The Grace Design m903 continues the tradition set by its predecessors by being 'a great, high-resolution DAC on a very cost-effective package' that offers remarkable clarity, continuity, and roundness of tone, and is better in almost every way than the m902."
- John Marks, Stereophile magazine, December 2011