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Mono MoDe

This feature sums the left and right channels on every set of outputs. Quite useful for checking for phase and balance issues in 

mixing and mastering. Or listening to Beatles records as they were originally mixed. To activate mono mode:

Push and hold the rotary encoder to enter the setup menu. Then rotate the encoder until you reach the mono mode screen, 
as indicated by the [ ] symbol.

Push and release the encoder to activate mono, which will be indicated by the illuminated decimal points [.].

Once you have activated (or deactivated) mono mode, either rotate the encoder to advance to the next setup menu item, or 
push and hold the encoder to exit the setup menu.

CroSSfeeD MoDe (x-feeD)

Please refer to the detailed description of this feature earlier in this manual. Crossfeed is only applied to the headphone outputs. 

This feature is toggled on and off in the setup menu, and its current status is preserved whenever the m903 is power cycled. To 

activate:

Push and hold the rotary encoder to enter the setup menu. Then rotate the encoder until you reach the crossfeed mode 
screen, as indicated by the letters CF.

Push and release the encoder to activate crossfeed, which will be indicated by the illuminated the decimal points C.F.

Once you have activated (or deactivated) crossfeed, either rotate the encoder to advance to the next setup menu item, or 
push and hold the encoder to exit the setup menu.

line oUtPUt MoDe

The rotary encoder is used to select and adjust the volume of the three available sets of outputs (headphones, line 1 and line 2). 

Depending of the output mode selected here, the two line outputs can either be selected and controlled independently of each 

other, or they can be grouped together and controlled in parallel. These options depend on how your m903 is installed – you may 

want to send the identical, parallel line outputs to two different input destinations (power amp, powered monitors, headphone 

distribution etc..). Or you may want independent control of two different sets of monitors (mains and nearfields). 
One interesting possibility for having the two line outputs grouped is a simple 2.1 monitoring setup - send one set to your moni-

tors and the other to a subwoofer. Use the level offset feature to trim either set of outputs accordingly.
To select between the two line output modes:

Push and hold the rotary encoder to enter the setup menu. Then rotate the encoder until you reach the two line output 
mode options, as indicated by the letters L1 or L2.

Push and release the encoder to toggle between either mode, which again we be indicated by the letters L1 or L2.  L1 is 
what refer to as ‘grouped’ operation, where both line outputs are selected and adjusted together in unison. L2 is what we call 
‘round robin, where each line output is selected and adjusted independently of each other.

Once you have selected the mode you require, either rotate the encoder to advance to the next setup menu item, or push 
and hold the encoder to exit the setup menu.

exClUSiVe oUtPUt MoDe

This mode allows you to toggle between all three outputs and mute the output not selected. The exclusive output mode can be 

very useful when referencing between the line outputs (controlling your speakers) and your headphones. Instead of having to 

manually mute or turn down the volume when toggling between outputs, this mode handles it automatically. Once enabled, 

selecting either line output turns that output on at its set volume and mutes the headphone outputs. Selecting the headphone 

output turns this output on at the set volume and mutes the line outputs. Note: the exclusive output mode is saved anytime the 

m903 is power cycled. To activate exclusive output mode:

Push and hold the rotary encoder to enter the setup menu. Then rotate the encoder until you reach the exclusive output 
mode option, as indicated by the letters EO.

Push and release the encoder to toggle on, which will be indicated by the illuminated the decimal points E.O. (push and 
release again to toggle off )

Once you have selected the output mode you require, either rotate the encoder to advance to the next setup menu item, or 
push and hold the encoder to exit the setup menu.

Summary of Contents for m903

Page 1: ...Owner s Manual Rev A all contents Grace Design Lunatec LLC 2434 30th Street Boulder CO 80301 USA www gracedesign com 303 443 7454 m903 reference headphone amplifier DAC monitor controller ...

Page 2: ...r website www gracedesign com for the latest Grace Design product information owner s manuals and technical documents Grace Design has been building audiophile quality products since 1995 The technology developed for the m903 has evolved through a process of extensive listening field testing and careful refinement Regardless of what type of moni toring you do your m903 will faithfully serve as an ...

Page 3: ...e and transportation temperature range 40 C to 70 C Maximum altitude 3000m 9843 ft Equipment suitable for continuous operation Weight 2 3kg 5lbs Safety Marking Symbols CAUTION READ ACCOMPANYING DOCUMENTS This symbol located on the equipment and in this manual refers to important instructions Read this manual thor oughly before operating this equipment WARNING ELECTRICAL SHOCK HAZARD This symbol lo...

Page 4: ...no electrolytic capacitors in the signal path Sealed gold contact relays are used for all signal switching Infrared remote control for level control left right balance mute and more when using the optional remote control unit 5 Year transferable warranty on parts and labor m903 Frontpanel Controls Features 1 ILLUMINATED POWER SWITCH illuminates green when unit is powered on 2 ROTARY INPUT SELECTOR...

Page 5: ...ng contact your grace design dealer and they will make sure you re taken care of Save your box We strongly encourage you to save the box and shipping materials supplied with your m903 They are specially designed to properly protect these valuable components and in the unlikely event that you need to return them for service only these OEM shipping materials can ensure their safe return to our facto...

Page 6: ... carrier with the proper line voltage showing through the small window Note that time delay or slow blow fuses are required Voltage and Fuse information CAM SETTING LINEVOLTAGE FUSEVALUE 110V 100 120V 250V T 250mA L 220V 220 240V 250V T 125mA L AC power cord Connect the supplied AC cord to the iec power entry module on the rear panel of the m903 For safety it is recommended that the cable be conne...

Page 7: ...Sleeve jacks These outputs are wired in parallel Connection to headphones should be made using standard TRS stereo connectors UNBALANCED LINE OUTPUTS A stereo pair of unbalanced line level outputs are provided via two RCA jacks These outputs should be connected to powered speakers or power amplifiers using standard unbalanced RCA cables BALANCED LINE OUTPUTS A stereo pair of balanced line level ou...

Page 8: ... 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 m903 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...

Page 9: ...time delay compared to the right ear As well the right speaker sound that reaches the left ear does not have a flat frequency response as the sound waves have traveled around the shape of your head before reaching your left ear The brain uses delay level and frequency response characteristics to process the location of a sound and hence create an aural image When listening through headphones each ...

Page 10: ... settings in non volatile memory and recalls these upon each power up Power Up Level This feature allows the user to save specific level settings for each output as the default power up level While default levels are set to 0 at the factory you may want to have the unit always power up at a specified level other than the default To program power up level settings 1 Push and hold the rotary encoder...

Page 11: ...ng off 3 Rotate the encoder to navigate to other setup menu items or push and hold to exit the setup menu Display dimmer mode The m903 features bright user interface designed to give you clear operational information However situations may exist when you want to turn off this display while keeping your unit running This is possible with the display dimmer mode With the display dimmer enabled all t...

Page 12: ...ontrol of two different sets of monitors mains and nearfields One interesting possibility for having the two line outputs grouped is a simple 2 1 monitoring setup send one set to your moni tors and the other to a subwoofer Use the level offset feature to trim either set of outputs accordingly To select between the two line output modes 1 Push and hold the rotary encoder to enter the setup menu The...

Page 13: ...ere you can control the setup menu in the same way as from the front panel volume encoder only with the volume up volume down buttons used to scroll and a single push of the PHONES LINE button serving as the enter switch Please refer back to the previous chapter ac cessing and using the setup menu for detailed information on how to navigate the setup menu Pushing and holding the PHONES LINE button...

Page 14: ... RX S PDIF INPUT TOSLINK INPUT s Lock PLL CLOCK AUDIO 24 bit 192kHz USB module INPUT SELECT INPUT SELECT CROSSFEED LINE OUTPUT LEVEL CONTROL HEADPHONE OUTPUT LEVEL CONTROL UNBALANCED ANALOG OUTPUT CROSSFEED ENABLE TRANSIMPEDANCE HEADPHONE AMPLIFIER Master clock MONO LINE OUTPUT LEVEL CONTROL 2 CHANNEL line 2 BALANCED LINE OUTPUT AMPLIFIER BALANCED ANALOG OUTPUT BALANCE LEVEL MUTE ANALOG INPUTS DIG...

Page 15: ...ne Out 116dB THD N Balanced Input Headphone Out 10dBu 50 Ohm load SMPTE 4 1 0 020 Headphone Out 10dBu 50 Ohm load 0 0060 Unbalanced Line Out 10dBu 100k Ohm load 0 00026 Balanced Line Out 20dBu 100k Ohm load 0 00036 Attenuator Channel matching 0 05dB Attenuator Range 97 5dB Output Noise Floor Balanced Input Balanced Output volume at maximum 22 22kHz 90dBu Balanced Output volume at minimum 22 22kHz ...

Page 16: ...ce at its option any defective parts or repair defective workmanship without charge provided the customer has appropriate proof of purchase and that the product has its origi nal factory serial number 4 In order for Grace Design to provide efficient and timely warranty service it is important that you mail the completed warranty registration card enclosed with all of our products within 10 days of...

Page 17: ...page 17 Manual Revisions Revision Page Change Date Initials A Initial release 12 20 2010 edg ...

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