m900 Headphone Amp / DAC / Preamp Owner’s Manual Revision B 04/27/2018 Grace Design / Lunatec LLC 4689 Ute Highway, Longmont, CO 80503 info@gracedesign.com www.gracedesign.com 1.303.823.
Contents 1 Welcome 2 Connections and Controls 1 2 2.1 REAR PANEL 2.2 FRONT PANEL 2.3 TOP PANEL 2 3 4 3 Operation 4 Using the Setup Menu 5 Specifications 6 Cleaning and Maintenance 7 Warranty Information 4 12 16 17 17 1 Welcome The m900 represents a new level of performance for compact, personal audio playback devices. With zero Ohm output impedance headphone outputs and a remarkable USB power supply design, the m900 delivers incredible playback performance with compact, stylish ergonomics.
2 Connections and Controls 2.1 REAR PANEL 1 2 3 4 5 1 - Line Outputs Unbalanced, level controlled line outputs via a pair of gold plated RCA phono jacks. These outputs are designed to connect to a power amp, powered speakers, preamps, or headphone amps. When headphones are connected to the right hand front panel jack, the line output signal is muted. 2 - S/PDIF Input Accepts up to 192kHz, 24 bit PCM digital audio signal. Automatic de-emphasis equalization.
5 - USB Connector #1 - Data / Signal / Bus Power Input Asynchronous USB 2 interface for bit perfect, zero interface induced jitter DAC operation. Accommodates 44.1kHz to 384kHz PCM and 64X - 256X DSD. Driverless operation with MAC OS. USB Class 2 operation with Windows up to 384kHz with free driver download from Grace Design. When nothing is connected to the USB connector #2, the m900 is bus powered through this interface and operates in Low Power mode. 2.
2.3 TOP PANEL 1 1 - Volume Control The top mounted rotary encoder provides precise, stepped level control. Its push-button feature is used to mute all signals (single push and release) or access the setup menu (push and hold). 3 Operation Unpacking Your m900 The m900 arrives in simple but protective Korrvu™ packaging. We recommend that you save this box in the event you wish to store or ship your unit in the future.
Headphone jacks are on the front and inputs and line outs are on the back, so your cabling can remain clean and simple. Powering Up Your m900 There is no power switch. Power is automatically applied when either of the USB jacks are connected. If you wish to power off the m900, simply disconnect the USB connection. The m900 can be powered from the your computer’s USB Bus in Low Power mode via the #1 USB connector. In this mode the internal supplies operate at lower voltage to conserve power.
Connecting Headphones There are 2 ¼” headphone output jacks on the front, which are wired in parallel. The second jack on the right is a switched type. If you have the line outputs connected to a power amp or powered monitors, connecting headphones to this jack will automatically mute the line outputs, allowing you to effectively ‘toggle’ between the headphone and speaker outputs. IMPORTANT NOTE: The m900 has very low output impedance, measuring around 0.08 Ohms.
Volume and Mute Control A high quality, light action stepped rotary encoder is used for volume and mute functions. Turn the knob clockwise to increase volume, counterclockwise to decrease the volume. A single push and release will mute all outputs. When the unit is muted, the 7 segment LED will dim and pulsate to indicate mute is active. Another single push and release de-activates mute. The m900 attenuator is a hybrid design.
Computer Configuration The m900 computer audio connection is an asynchronous USB interface. With asynchronous mode USB operation, the m900 USB DAC becomes the clock master to which the computer’s USB bus is synced. The computer is synced to a crystal-based audio clock signal and the system works with dramatically lower jitter. No phase-lock loop or sample rate conversion is necessary, which means bit-perfect playback from a computer with effectively zero interface induced jitter.
Installing the Windows USB driver To download the Windows driver, visit our support page- http://www.gracedesign.com/ support/support.htm. Under m900, locate and save the driver file titled ‘XMOS Stereo USB Audio Class2 Driver’. Begin with your m900 disconnected from your computer. Double click on the driver file to run and follow the instructions in the installation dialog: 1. Open install dialog. 2. Accept terms and click next.
3. Choose default location and install. 4. Installation Complete. 5. Connect your m900. 6.
Once you have successfully installed your driver, you will have the option to operate your m900 in USB 1 mode or USB 2 mode, which are selected in the m900 setup menu (see ‘using the setup’ menu below). These modes will show up in the OS playback settings differently: In USB 1 mode, the m900 will show up in the OS playback device dialog as ‘m900’.
4 Using the Setup Menu Navigating the Setup Menu The m900 provides several setup and calibration options, which are adjusted in the setup menu. The setup menu is accessed by the top panel volume encoder. To enter the setup menu, simply push and hold the volume encoder for 2 seconds. The 7 segment LED screen will change from the current level readout to the current setup menu item.
= Right to both channels = Left channel only = Right channel only INPUT SOURCE SELECT Toggles between the 3 available audio inputs - USB, TOSLINK or S/ PDIF. In the Setup Menu, push and release the encoder to select input source. = USB input = TOSLINK input = S/PDIF input DISPLAY DIMMER MODE Turns off the 7 segment display after 5 seconds of inactivity. Turning or pushing encoder re-illuminates the display. Push and release the encoder to toggle the setting.
pressed, and with lots of treble. Will contain substantial ringing before and after transients (pre-echo and post-echo). Note that the ringing occurs at the Nyquist frequency (½ of the sample rate), so it is not directly audible. However, it can cause intermodulation distortion in downstream components. = slow roll off, linear phase For linear phase response and time coherency. Best for acoustic music without compression and artificially high levels of treble.
Because the m900’s display is only 2 characters, the higher sample rates are abbreviated as the following: = (176kHz) = (192kHz) = (354kHz) = (384kHz) DSD rates are shown as: = (DSD64) = (DSD128) = (DSD256) PAGE 15
5 Specifications THD+N 1kHz, 22Hz-22kHz BW @1.0V out, no load @1.0V out, 32 Ohm load Intermodulation Distortion SMTPE/DIN 4:1 50Hz, 7kHz @1.0V out, no load @1.0V out, 32 Ohm load Frequency Response +/-3dB Fs=96kHz Dynamic Range 20-22kHz bandwidth 20-22kHz bandwidth and A weighting filter Output Noise 20-22kHz, volume=0-90 A weighting filter, volume = 0-90 20-22kHz, volume=90.5-99.5 A weighting filter, volume = 90.5-99.5 Crosstalk 100Hz 1kHz 20kHz Attenuation Range 0 to -99dB, 0.
6 Cleaning and Maintenance Your m900 chassis is constructed out of high quality anodized aluminum and steel. Under normal circumstances, very little maintenance is required to keep it looking good. However, if you find it getting more dirty or dusty than you like, here are some cleaning tips: We recommend using a little shot of Windex™, applied to a clean, dry, lint free cloth. Gently wipe all surfaces, taking care not to allow the cleaning product to build up around or under the knob or chassis seams.
