Grace Design m905 Monitor Controller

This is the world’s finest stereo monitor controller, with built in mastering quality Digital to Analog Converters, audiophile-grade headphone amplifier and unrivaled system configuration tools. For hardworking audio professionals and studios that demand the very best playback available.

Two new product options are now available:

m905 Analog* (analog inputs only)

Infrared wireless remote option**

The is our second generation stereo monitor controller, engineered from the ground up to provide unrivaled sonic purity with a comprehensive and powerful feature set.

The m905 represents a new benchmark for audio playback quality. DAC performance is on par with the finest esoteric mastering equipment available. Our redesigned s-Lock™ PLL ensures ultra-low jitter clock regeneration. An asynchronous USB class 2 interface allows the m905 to act as the master clock of the computer’s USB audio buss, effectively eliminating interface induced jitter for computer audio playback. And finally, meticulous analog circuitry measures with outstanding numbers in dynamic range, distortion and noise performance, ensuring bracingly open, detailed and musical playback of any input source.

All main audio and power supply circuitry is housed in a 2U rack mount mainframe, while system control is managed by a sleek, ergonomic remote control unit. This new RCU is a combination of dedicated hardware and a color graphical LCD display. All primary monitoring features are accessed via hardware switches and a rotary encoder, while all system information is presented by the graphic LCD and illuminated switches. This hybrid design allows for the solid feel and function of traditional hardware with the added power and functionality of a graphical user interface.

Now supported is DSD 128x (5.6448MHz) via DoP v1.1 (DSD over PCM frames). DSD audio can be sourced from the AES3, S/PDIF or USB digital inputs. While still a niche playback format, DSD has held its ground over the years, and now more and more content is available via download. And playback is now supported by a number of players. DSD sounds stunningly natural, especially rendered through the rest of the playback circuitry of the m905. So If you’re the type to seek out this kind of fidelity, we can’t recommend it enough.

The GUI is designed so that any engineer unfamiliar with the m905 can use the system immediately and confidently. Then with a minimal time investment, advanced functions can be accessed and controlled with ease. Additional features include: naming individual inputs and speaker outputs, calibrating level offsets of any input and output, setting preset levels, and much more. The setup menus only ever drill down one level, so the main operating screen is always one button away. And when returning to any previously visited setup menu, its previous edit status is remembered, keeping redundant navigation and editing to a minimum.

The m905 offers the ability to transfer up to 10 channels of digital audio (8-channels of ADAT and two of AES3, or S/PDIF or TOSLINK) over USB to a computer, making the m905 capable of operating as a standalone USB audio interface. This is an advanced feature as there are clock issues to be aware of, but it works and is documented in the owners manual.

With stunning sonic performance and timeless design, the m905 is a mark of genuine progress in the pursuit of high quality audio production. Intuitive, reliable and beautiful, it is the perfect studio centerpiece – home base for your ears, eyes and hands.

*the m905 Analog is now available without the built in DAC. This system is offered for users who already have an investment in DACs, whether stand-alone or built into their interface. System configuration is exactly the same, with all the same great monitoring features, except no digital input and an second pair of balanced analog inputs. The m905 Analog brings this world class performance into reach of almost any engineer or recording studio. Also, users can always upgrade their m905 Analog to the Digital version at anytime.

**Also now availabble is the m905 IR Remote Option, which is available on new or existing units (Digital and Analog). This feature allows wireless infrared remote control of a select set of monitoring controls via the Grace Design Remote, a standard Apple Remote, or with iOS and Android via the Logitec® Harmony Remote.

Features

• Analog inputs – unbalanced, balanced, CUE, talkback mic (additional balanced input available on the m905 Analog)
• Digital inputs – 2x AES3 (Single or dual-wire), 1 S/PDIF, 1 TOSLINK, ADAT (selectable in 4 pairs, or 2 pairs in S/MUX), USB, DSD128 (5.6448MHz)
• Audio circuitry designed for completely transparent and musical playback performance
• Asynchronous Class 2 USB playback supports up to 24 bit/192kHz
• Mastering quality DAC circuitry with configurable de-emphasis filtering
• s-lock dual-stage Phase Lock Loop for ultra low jitter clock regeneration
• Hybrid RCU with hardware switches, large level encoder and graphical LCD
• LCD display shows input, level, output, SPL and DAC status plus a full calibration menu
• RCU includes built in microphone for talkback and onboard SPL meter
• SPL meter features include level, peak, fast and slow modes, A & C weighting
• Precision .5 dB step level control for speakers and headphones
• Reference headphone amplifier circuitry, with outputs on both the RCU and ACU
• Dedicated mono, dim, mute and sub mute switches
• Mono mode can be set to L+R summed, L only in both channels, or R only in both channels
• L solo, R solo, L-R and sub solo modes are available
• 3 available stereo speaker outputs, with two assignable mono sub outputs (or single stereo sub output)
• Multi-mode SUB/ DAC/ METER out
• SUB out mode for stereo or multiple mono subwoofer outputs
• DAC out mode for a fixed DAC output fed by the selected digital input
• METER out mode fed by selected input signal (digital or analog), configurable with a fixed level or to follow the monitor level
• Detachable RCU tilt base

Specifications

ANALOG I/O
THD+N at Maximum Volume, 1kHz, 22Hz-22kHz BW
+20dBu out	<0.0008%
+10dBu out	<0.0008%
0dBu out	<0.002%
Intermodulation Distortion SMTPE/DIN 4:1 50Hz, 7kHz
@+20dBu out	<0.002%
@ 0dBu out	<0.0015%
Frequency Response
Balanced Inputs +/-3dB	3Hz to 1.25MHz
Unbalanced Input +/-3dB	3Hz to 275kHz
Dynamic Range
20-22kHz bandwidth	118dB
20-22kHz bandwidth and A weighting filter	121dB
Output Noise
20-22kHz bandwidth, at -20dB gain	-99dBu
20-22kHz bandwidth and A weighting filter, at -20dB Gain	-102dBu
Phase Deviation
20Hz to 20kHz	<10 degrees
10Hz to 100kHz	< 19 degrees
Crosstalk any channel
100Hz	<104dB
1kHz	<100dB
20kHz	<79dB
Balanced Input CMRR
60Hz	>90dB
1kHz	>85dB
10kHz	>70dB
Gain Range	-104dB to +13dB
Channel Tracking Accuracy
Any channel	+/-0.1dB
Maximum Output Level	+26dBu
Maximum Input Level
Balanced inputs	+29dBu
Unbalanced inputs	+21dBu
Impedances
Balanced inputs	88k Ohms
Unbalanced inputs	53k Ohms
Balanced outputs	300 Ohms
Minimum load impedance	300 Ohms
External Talkback Mic Preamp Gain	+7dB to +70dB in 1dB steps
DIGITAL TO ANALOG CONVERTER FIXED OUTPUTS
Output Levels
User selectable (0dBFS)	-76dBu to +24dBu in 0.5dB steps
Fixed output trim range (0.5dB steps)
THD+N
1kHz, -1dBFS, (0dBFS = +20dBu), 20-22kHz bandwidth	0.0006%
Dynamic Range
20-22kHz bandwidth, 0dBFS = +20dBu (AES17 filter)	117dB
20-22kHz bandwidth, 0dBFS = +20dBu (A-weighted)	119dB
Input Lock Range
AES3/SPDIF	44.1kHz +/-400Hz 48kHz +/-700Hz 88.2kHz +/-1200Hz 96kHz +/-1300Hz 176.4kHz +/-2000Hz 192kHz +/-2000Hz
TOSLINK	44.1kHz +/-400Hz 48kHz +/-700Hz 88.2kHz +/-1200Hz 96kHz +/-1300Hz
ADAT LIGHTPIPE™ 8 Channels at 44.1kHz and 48kHz 4 Channels at 88.2kHz and 96kHz (s/mux)	44.1kHz +/-50Hz 48kHz +/-70Hz 88.2kHz +/-50Hz 96kHz +/-70Hz
USB Supported Sample Rates	44.1, 48, 88.2, 96, 176.4, 192kHz, DSD64 2.8224MHz, DSD128 5.6448MHz
s-Lock™ Capture Range
44.1kHz	+/- 6Hz
48kHz	+/- 7Hz
88.2kHz	+/- 14Hz
96kHz	+/- 20Hz
176.4kHz	+/- 24Hz
192kHz	+/- 30Hz
Word Clock / Superclock Input
Impedance (switchable)	75 ohm / 1Meg ohm
Minimum Voltage	3V peak to peak
Maximum Voltage	5V peak to peak
Word clock frequencies supported	44.1, 48, 88.2, 96, 176.4, 192kHz
Superclock frequencies supported	N/A
POWER SUPPLY / GENERAL
Power consumption	60W
Input Voltage 50-60Hz	100VAC – 240VAC
Dimensions
Main chassis IEC 2U	3.5″ x 10.5″ x 17″
Remote control unit	8.9″ x 5.1″ x 2.2″
Weight
Main chassis	7.8lbs
Remote control unit	2.2lbs

Computer Setup

Asynchronous Audio

The asynchronous mode USB converter in the m905 represents significant improvement over any previous type of USB DAC. Previously, a USB DAC worked under standard adaptive mode USB audio, which means the DAC’s clock would have to sync to the non-audio related computer USB buss master clock. As you can imagine, the computer has a lot else to do, so the incoming clock signal to which the DAC’s clock would have to sync was not ideal and would result in unwanted jitter.

With asynchronous mode USB, the m905’s USB DAC becomes the master to which the computer’s USB buss gets synced. So the computer is now synced to a crystal-based audio clock signal and the systems works with dramatically lower jitter. No phase-lock loop or sample rate conversion necessary, which means bit-perfect playback from a computer with zero interface-induced jitter.

Computer Audio Requirements

Regardless of the type of computer you will use to playback audio from, it must have at least one available USB port. The m905 ships with a standard USB type A to type B cable. The type A connector plugs in to the computer and the type B connector to the USB m905 input.

The m905’s asynchronous mode USB DAC supports standard driverless operation on MAC to 192kHz and on PC to 96kHz. For sampling rates above 96kHz, PC users will need to download and install a free driver on their computer. This driver can be found on our website – https://www.gracedesign.com/support/support.htm Driverless operation basically means ‘plug and play’. The m905 will automatically show up in your computer’s list of supported audio devices as ‘Grace Audio Device’. In most cases, simply choose that as your audio playback device and the system will work.

Different operating systems may pose their own set of complications in setting up the m905 as the audio playback device. In the event that ‘plug and play’ operation does not occur, you will need to look at some specific setup variables for your OS. In this case, we will direct you to a very well written and comprehensive docu­ment by our friend and colleague Charlie Hanson from Ayre Acoustics. https://www.ayre.com/USB.htm. This is an invaluable resource for computer/USB audio setup information for most all current operating systems, and we strongly urge you to familiarize yourself with the information pertaining to your specific OS.

Another excellent resource is Wavelength Audio’s website: https://www.USBdacs.com In the event that you have any setup issues which aren’t addressed by these resources, feel from to contact us directly at 303.443.7454 Monday through Friday 9 – 5, MST.

Using the m905 for DAW playback

With the extremely high quality audio playback achieved with this USB interface, the m905 can be great option as an stereo output device directly from your digital audio workstation. For playback only, this will work very well. However, using it in conjunction with other USB audio devices connected to your workstation computer’s USB will require some adjustments to your computers audio settings and for best results, some external clock routing between audio devices. For Mac OS X, this is achieved by setting up the m905 in an ‘aggregate audio device’ setup, with the m905 as the output device. For Win 98 – Win 7, you must use ‘asio4all’ drivers- https://www.asio4all.com/. There is currently no support yet for windows 8.

With both of these setups, if you are using multiple I/O devices, you will need to pay careful attention to clocking. In Mac / Core audio aggregate setups, you are able to set which device is the clock master. However, this means that other devices will be sample rate converted, which we do not recommend.