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Grace Design m900 Portable DAC and Preamp  From Grace

The m900 is a compact, portable headphone amp with an incredibly clear DAC

Grace Design


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Manufacturer's Description from Grace

The m900 is a portable, desktop-friendly headphone amplifier / DAC / preamp combo designed to give audio professionals and enthusiasts musical and transparent audio playback from USB, S/PDIF or TOSLINK sources. For small DAW studio setups, portable laptop editing or mixing rigs, or just pure playback enjoyment, the m900 provides the same analog and DAC quality as our large monitor controllers, but in a rugged, portable and surprisingly affordable unit.

The m900 DAC uses the latest generation AKM 4490 chip, which features 32-bit processing and supports sample rates up to 384kHz PCM or 256x DSD. The USB interface operates in an asynchronous mode allowing the m900 to be the clock master which makes the system immune to USB bus jitter. S/PDIF and Toslink inputs allow the m900 to enhance any DAW interface with true reference quality D/A conversion, headphone monitoring, and stereo speaker control.

An intelligent power supply design allows for two power operation modes - LOW and HIGH. LOW power mode is from USB connector #1, which provides bus power along with data, allowing the m900 to operate from a single connection to your computer. HIGH power mode is available by connecting the included 2A USB DC power supply to the USB connector #2, which provides additional power for harder to drive headphones.

Transimpedance amplifier topology coupled to a zero ohm output impedance driver provides headphone performance that is incredibly spacious and transparent with a tight, enveloping low end. Our latest generation crossfeed circuit rounds out the design by simulating an acoustic listening environment in the headphones. Familiar tracks become new again with surprise details, while audio production tasks like tracking, mixing and editing happen faster and easier.

After many years of honing our DAC and headphone amplifier designs, the m900 distills the best of what we've learned in a compact, rugged and simple unit. Whether in the studio, on your desk or on the road, the m900 will bring you closer to the music you love.

• USB, S/PDIF, and Toslink digital inputs support up to 192kHz (Toslink up to 96kHz)

• Asynchronous USB interface for jitter-free computer audio playback supports up to 384kHz PCM and 256x DSD

• Dual zero ohm output impedance headphone outputs

• Unbalanced level controlled outputs via RCA for connecting to a stereo monitor system

• Compact, portable chassis perfect for travel, desktop or studio

• Low power mode via USB Bus power

• High power mode via included USB 2A power supply

• 4 different DAC filter settings to tailor playback performance to personal preference

• Simple user setup menu for setup and calibration

• 7 segment LED display displays level and setup menu information

• A large rotary encoder for volume control and setup menu navigation

• Made in Lyons, CO USA

• 5-year transferable Warranty

Grace Design

About Manufacturer

Audio engineer/designer Michael Grace originally began building single order custom audio products for a small, devout following of recording engineers and artists is 1990. Before long, the word had spread about Michael's custom microphone preamplifier designs, which were said to outperform anything else that was commercially available. Based on an increasing demand for his mic preamp design, in 1994 Grace Design was founded and began production of the original 801 mic preamp. Not only did the 801 provide a new level of audio performance and functionality, it helped to establish outboard microphone preamplifiers and direct-to-tape recording as a new standard in professional audio production. Over the years, Grace Design has maintained a steady, methodical pace to developing new products and technologies. Our product line has evolved into a definitive collection of microphone preamplifier configurations and other unique professional audio products. While the professional audio industry is inundated with products seemingly designed for obsolescence, we pride ourselves on providing audio professionals with the finest tools imaginable. Located in Boulder, Colorado, Grace Design continues its mission into the new millennium. As our company grows, we continually strive to improve our production methods to make sure theya re exact, efficient and environmentally sound. Their employees are treated like family and they strive to improve our production mehods to make sure they are exact, efficient and environmentally sound. Our employees are treated like our family and we strive to maintain our business relationships as friendships. And above all, we remain driven by the original passion that founded the company- the love of music.


• HD+N 1kHz, 22Hz-22kHz BW

@1.0V out, no load <0.002%

@1.0V out, 32 Ohm load <0.010%

• Intermodulation Distortion SMTPE/DIN 4:1 50Hz, 7kHz

@1.0V out, no load <0.008%

@1.0V out, 32 Ohm load <0.009%

• Frequency Response +/-3dB

Fs=96kHz 0.5-45.9kHz

• Dynamic Range

20-22kHz bandwidth 112dB

20-22kHz bandwidth and A weighting filter 115dB

• Output Noise

20-22kHz, volume=0-90 -106dBV

A weighting filter, volume = 0-90 -109dBV

20-22kHz, volume=90.5-99.5 -96dBV

A weighting filter, volume = 90.5-99.5 -98dBV

• Crosstalk

100Hz <107dB

1kHz <98dB

20kHz <72dB

• Attenuation Range

0 to -99dB, 0.5dB steps 

• Channel Tracking Accuracy


• Maximum Output Level, No load

Low Power Mode+14.1dBV (5.1V)

High Power Mode+15.5dBV (6.0V)

• Impedances

Headphone Output0.08 Ohms

Line Output        47.5 Ohms

• Input Lock Range            Sample Rate         Lock Rnage

S/PDIF                              44.1kHz           43870-45420Hz
                                        48kHz              46590-49220Hz
                                        88.2kHz           87760-90830Hz
                                        96kHz              93520-98430Hz
                                        176.4kHz         175700-181640Hz
                                        192kHz            187050-196380Hz
                                        44.1kHz           43900-45410Hz
                                        48kHz              46590-49190Hz
                                        88.2kHz           87840-90830Hz
                                        96kHz              93520-97530Hz

USB supported sample rates44.1, 48, 88.2, 96, 176.4, 192, 352.8, 384kHz

• Power Consumption

Max, High Power mode8.0W

Max, Low Power mode2.5W

• Dimensions

4" x 5.25" x 1.8"

Load Resistance Ohms 1 Channel Driven 2 Channels Driven
4 80 22
8 140 45
16 310 90
20 350 100
32 600 175
50 560 280
300 83 83
600 40 40
Headphone Output Power / High Power Mode Output Power mW  
Load Resistance Ohms 1 Channel Driven 2 Channels Driven
4 925 240
8 1800 490
16 1900 940
20 1575 1030
32 1020 950
50 680 650
300 115 115
600 57 57