Grace Design m905 Users Manual
Digital and Analog Versions
Owner’s Manual Revision D
ACU Firmware v1.13
RCU Firmware v1.13
XMOS Firmware v1.13
1 Welcome
Welcome and thanks for purchasing the Grace Design m905 reference monitor controller. We build all
of our products to be completely reliable and straightforward to use, so you can concentrate on doing
great work. While you will nd the m905 is fairly straightforward to use, it is a very powerful unit and a
great deal of user conguration is possible, so we recommend that you spend some time reading this
manual to help avoid any common user diculties.
In the event that you do encounter any technical diculties with this or any of our products, feel free to
call us at 303-823-8100. Our oce hours are 9:00 to 5:00, Monday through Friday, MST, or you may email any technical questions to: info@gracedesign.com. Also, please check out our website for complete
product information, owner’s manuals and technical documents http://www.gracedesign.com
Grace Design has been building audiophile quality products for the recording industry for over 20 years.
The technology in the m905 is the result of extensive research, listening, testing and careful renement.
Your m905 represents a combination of absolutely pristine audio performance, robust mechanical
construction and complete reliability. We sincerely hope it helps you achieve a new level of excellence
in your work!
Contents
1 WELCOME 2
2 IMPORTANT SAFETY INFORMATION 3
3 SAFETY MARKING SYMBOLS 3
4 SERVICE INFORMATION 3
5 M905 FEATURES 4
m905 Audio Control Unit Rear Panel 5
Audio Control Unit Front Panel 6
Remote Control Unit (RCU) 6
m905 Graphical User Interface 7
7 UNPACKING AND INSTALLING 8
Your m905 Box Will Contain 8
Open and Inspect the Box 8
Register Your Unit 8
8 CONNECTING THE M905 8
Power Connections 8
Power-Up Sequence 8
System Connections 9
9 NORMAL OPERATION MODE 11
Input Selection 11
Volume Control, Preset & Headphone Mute 11
Speaker Output Selection 12
Monitoring Option Controls 12
Display 14
Save / Recall of User Configuration 15
Optional IR (infrared) Remote Control Operation 15
Analog Only Option 17
10 SETUP MODE 17
Entering and Exiting Setup Mode 17
Input Setup 18
Speaker Setup 20
Dim Setup 21
SUB / DAC / METER setup 21
CUE Output Setup 22
Headphone Setup 23
Talkback Setup 24
Mute / (solo) 24
11 GENERAL SETUP 25
Display Setup 25
IR (infrared) Remote Setup 25
DIGI LOOP Setup 26
Digital Input Setup 26
System Setup 27
SPL Meter Setup 27
12 ABOUT CROSS-FEED 28
13 COMMUNICATION ERROR HANDLING 29
14 COMPUTER AUDIO SETUP 29
Asynchronous USB Audio 29
USB Up Channel Setup 30
Computer Audio Requirements 31
Using the m905 for DAW playback 32
15 UPDATING FIRMWARE 32
Updating RCU Firmware 33
Updating ACU Firmware 34
Updating XMOS Firmware 35
16 SPECIFICATIONS 37
17 BLOCK DIAGRAM 39
18 PCB JUMPER LOCATIONS 40
19 WIRING DIAGRAMS 41
20 CLEANING AND MAINTENANCE 42
21 WARRANTY INFORMATION 42
22 MANUAL REVISIONS 43
2
2 Important Safety Information
• Indoor use only
• Ordinary Protection: This equipment should not be exposed to dripping or splashing
• Avoid placing objects filled with liquids, such as vases or glasses, on this equipment
• Class I Equipment (grounded type)
• Electrical rating: 100-240V~ 50-60Hz 60W
• Mains supply voltage fluctuations are not to exceed ±10% of the nominal supply voltage
• Pollution Degree 2
• Installation (Overvoltage) Category II for transient overvoltages
• Maximum Relative Humidity: <80%
• Operation temperature range: 10 °C to 40 °C
• Storage and transportation temperature range –40 °C to 70 °C
• Maximum altitude: 3000m (9843 ft)
• Equipment suitable for continuous operation
• Weight: ACU 7.8lbs, RCU 2.2lbs
3 Safety Marking Symbols
CAUTION: READ ACCOMPANYING DOCUMENTS This symbol, located on the equipment and
in this manual, refers to important instructions. Read this manual thoroughly before
operating this equipment.
WARNING: ELECTRICAL SHOCK HAZARD This symbol, located on the equipment and in this
manual, indicates the potential for electrical shock hazard.
4 Service Information
The Grace Design m905 contains no user serviceable components. Contact Grace Design for repair and
upgrade information. In the event that your Grace Design m905 needs to be returned to the factory, contact
us for a return authorization number.
3
5 m905 features
• Analog inputs - unbalanced, balanced (2nd pair balanced available on m905 Analog) , CUE, talkback mic
• Digital inputs - 2x AES3, 1 S/PDIF, 1 TOSLINK, ADAT (selectable in 4 pairs, or 2 pairs in S/MUX), USB, AES3
Dual Wire mode. AES and S/PDIF connectors support DSD64 or DSD128 via DoP Version 1.1
• Audio circuitry designed for completely transparent and musical playback performance
• Asynchronous Class 2 USB playback supports up to 24bit /196kHz and DSD64 or DSD128 via DoP Version
1.1, configured for two channels down from computer and 10 channels up to computer
• 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, volume displayed in absolute or custom
reference level
• 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
• Optional IR (infrared) remote control via Grace Design Remote, Apple Remote or iOS and Andriod with the
Logitech Harmony Hub Remote
• 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
• Five year transferrable warranty
4
M905 AUDIO CONTROL UNIT REAR PANEL
1
2
3
4
5
7
6
8
9
10
11
12
13
100-240 VAC / 50-60Hz
60 Watts Max
GRACE DESIGN
LYONS, CO USA
Pb
RoHS
COMPLIANT
UPGRADE
1M
75
WORDCLOCK
REMOTE
14 15
OUT
IN
TALKBACK SWITCH
16 17 18 19
DIGITAL IN
AES 2AES 1 S/PDIF TOSLINK
L
R
24
100-240 VAC / 50-60Hz
60 Watts Max
GRACE DESIGN
LYONS, CO USA
Pb
RoHS
COMPLIANT
REMOTE
L
BALANCED IN 2
TALKBACK SWITCH
R
L
R
1 AC mains input universal 100-240 VAC, 50-60Hz, 60
Watts max. This connects m905 (with the supplied AC
power) cable to AC power source.
2 Word Clock termination switch used to properly ter-
minate a connection from an external clock reference
source to the m905 Word Clock input.
3 Word Clock input for incoming word clock signals from
a master clock or other equipment passing a master
clock signal.
4 Word Clock output for sending or passing word clock
signals from the m905 to other equipment.
5 Two AES3 input XLR connectors used to receive stereo
AES3, Dual Wire AES3, and DSD64 or DSD128 via DoP
V1.1
6 */PDIF INPUT RCA jack input accepts a S/PDIF format
digital stereo signal or DSD64 or DSD128 via DoP V1.1
7 TOSLINK INPUT Optical connector accepts a TOSLINK
format digital stereo signal.
8 ADAT INPUT LIGHTPIPE™ connector provides a 2 chan-
nel input selectable in 4 pairs (or 2 pair S/MUX) of an
ADAT format digital source.
9 USB Class 2 interface provides an asynchronous mode
computer interface PCM up to 24bit/196kHz and
DSD64 and DSD128 via DoP V1.1. Configured for two
channels down from computer and 10 channels up to
computer.
10 Digital out provides a buffered digital loop-through of
a selected source via AES or S/PDIF.
SUB/
DAC OUT
L
R
CUE INSPEAKER 1 BALANCED IN
20 21 23
SUB/
DAC OUT
L
L
R
CUE INSPEAKER 1 BALANCED IN
CUE OUT
L
R
L
R
L
R
R
UNBAL IN
22
CUE OUT
L
R
L
R
L
R
R
ADAT USB 2
L
SPEAKER 2 SPEAKER 3
L
L
R
L
R
DIGITAL OUT
S/PDIF AES3
L
R
R
11 Multi-mode SUB / DAC / Meter output can be used as
either a subwoofer output (mono or stereo), a fixed
level DAC output, or a dedicated meter output. Configurable in the setup menu.
12 Cue out stereo output includes sum of the CUE input
signal with talkback mic signal.
13 Talkback output mono output of talkback microphone
signal.
14 USB upgrade port for future ACU firmware revisions.
15 DB15 Remote connector connects the m905 ACU and
RCU with supplied 15 pin serial remote cable
16 Talkback switch input, momentary or latching opera-
tion, configured in the setup menu.Speaker 1 output
stereo balanced
17 Speaker 1 output stereo balanced
18 Speaker 2 output stereo balanced
19 Speaker 3 output stereo balanced
20 Cue input for studio headphone mixes, sums with
talkback mic signal for CUE output.
21 Analog Balanced Input via XLR connectors.
22 Analog Unbalanced input via RCA connectors.
23 External Talkback mic input, for any type of external
microphone, 7-70dB gain, 48V configurable in the
setup menu.
24 m905 Analog Rear panel - digital inputs are not avail-
able - a second set of balanced Analog inputs via XLR
is installed.
TALKBACK OUT
TALKBACK MIC IN
TALKBACK OUT
TALKBACK MIC INUNBAL INUPGRADE SPEAKER 2 SPEAKER 3
5
AUDIO CONTROL UNIT FRONT PANEL
REFERENCE MONITOR CONTROLLER
GRACE DESIGN USA
1
HEADPHONE OUTPUT standard TRS 1/4” jack for headphones. Wired in parallel with the jack on the RCU.
Connection to headphones should be made using
standard ¼” TRS stereo connectors.
REMOTE CONTROL UNIT (RCU)
1 2 3 4 5
10 11 12
SPEAKER 3
1
2
2 AC mains power standby switch Illuminates green
when m905 system is powered on. ALL SYSTEMS GO!
13 14 15
SUB MUTE
MUTE SETUP
solo
sub solo
16
MON > CU ESPEAKER 2
MONO
VOLUME
push for p hones
L - R
17
spl clear
TALKBAC K
18
6 7 8 9
19 20 21
SPEAKER 1
DIM
x-feed
Note: for all the dual function buttons on the RCU, the primary push release function illuminates solid, and the
push and hold function flashes.
1 Graphical user interface (GUI) This color LCD displays
all operating parameters and setup menus.
2 Analog input unbalanced selects input source con-
nected to the unbalanced RCA analog input.
3 Analog input balanced selects input source connected
to the balanced XLR analog input.
4 CUE input selects input source connected to the bal-
anced XLR CUE input.
5 TOSLINK input selects input source connected to the
TOSLINK optical input.
6 ADAT / AES DW INPUT When ADAT mode is active se-
lects ADAT format digital stereo signal. Once selected,
pushing the switch toggles through available input
pairs. When AES Dual Wire mode is active, AES DW
selects the Dual Wire source connected to the AES1
and AES2 inputs.
7 S/PDIF selects input source connected to the S/PDIF
RCA style connector
6
8 AES selects the last used AES source. Once selected,
pushing the switch toggles between AES1 and AES2.
9 USB selects computer input source connected to the
USB connector.
10 Speakers 1, 2, 3 illuminated switches select any one
pair of the three available speaker outputs.
11 Mute / solo switch mutes the speakers or press and
hold to toggle solo channel.
12 Dim / x-feed reduces the monitoring level by a
prescribed amount. Press and hold to toggle on / off
cross-feed in headphones.
13 Sub-mute / sub-solo button mutes the subwoofer.
Press and hold solos the subwoofer.
14 MONO sums to mono (L+R) the current signal being
monitored. Press and hold subtracts the right channel
from the left channel (L-R).
15 SETUP enters the setup menu.
m905 GRAPHICAL USER INTERFACE
1
16 MON>CUE routes currently selected monitor source to
the CUE output. Press and hold to clear SPL peak level.
17 Volume adjusts speaker and headphone levels. Push
to toggle between either level. On speaker, press and
hold recalls volume preset. On headphones if level is
0.0, push and hold recalls headphone preset. If headphones are on, press and hold toggles headphone
mute.
18 Talkback activates the talkback microphone, either
built in or external.
19 DB15 serial connector connects RCU to ACU with sup-
plied 15 pin serial cable.
20 1/4” TRS headphone jack wired in parallel to head-
phone jack on frontpanel of ACU. Note: this output is
not connected on standard m905 Analog units unless
RCU cable upgrade is purchased
21 USB upgrade port for future RCU firmware revisions.
6
4
2
3
5
1
1 Input buttons - these 2 rows at the top and the bottom
of the screen represent the available system inputs.
Each button directly corresponds to its particular
input select switch and its corresponding input source.
Custom labeling is available via the setup menu. Active
input button is a friendly shade of blue.
2 Main speaker level and speaker set - this area shows
the current speaker set selected and the current
monitoring level in 0.5dB steps. When the standard
level display mode is active (configured in SETUP) the
range is 0-100. When reference level display mode
is configured the display range is user defined. See
Speaker SETUP for more information. Level numbers
highlight green when selected and are adjustable via
the volume encoder.
3 SPL meter - this area shows the current SPL level, me-
tering mode, and peak level. Setup menu allows user
to select between A and C weighting, fast and slow
mode. Resetting peak level is done by pushing and
holding the ‘MON>CUE’ hardware switch.
6
4 Headphone level and x-feed status - this area shows
the current headphone monitoring level (0-100dB in
.5dB steps) and cross feed status (push and hold ‘DIM’
hardware switch to activate / deactivate crosssfeed).
Level numbers highlight green when selected and are
adjustable via the volume encoder.
5 DAC clock status - this area displays the main clock-
ing functions and status of the m905’s DAC. Top row
displays the selected digital input source, S/MUX
(if enabled) and de-emphasis (if enabled). Second
row displays the DAC’s operating sampling rate and
s-Lock status if active. Third row displays the selected
clocksource and selected clocksource lock status.
Fourth row displays the bitstream status: pro/cons (for
TOSLINK, S/PDIF AND AES), S/MUX (for ADAT) and deemphasis (for TOSLINK, S/PDIF AND AES).
6 m905 Analog screen showing digital inputs are not
available. Available analog inputs are automatically
shifted the the bottom row.
7
7 Unpacking and Installing
YOUR m905 BOX WILL CONTAIN
• The Audio Control Unit (ACU)
• The Remote Control Unit (RCU)
• The RCU tilt base and accompanying hardware, premounted to the RCU
• 25’ serial cable to connect the RCU and ACU
• m905 Analog comes with an ethernet cable and 2 serial adapter jacks . For RCU headphone operation a
RCU cable ugrade is required. This is available from youe dealer or from the Grace Design factory)
• 6’ AC power cable which connects to the ACU’s universal power supply
• A bag with rubber feet and rack screws
• The owner’s manual and warranty registration
OPEN AND INSPECT THE BOX
Please take care when removing the m905 from its OEM packaging. Our packaging is designed with
‘Korrvu©’ suspension inserts, which provide the best protection from the dubious underworld of freight
handling – so save your packaging material. Inner boxes will contain all the items listed above. If you
think you are missing anything, give your dealer or us a call and we’ll get you taken care of right away.
REGISTER YOUR UNIT
Also, we strongly urge you to ll out your warranty registration card. We provide a 5 year transferable
warranty on all of our products, but without your registration it’s hard for us to help you if and when
help becomes necessary. So please take a few minutes to complete and send in the enclosed card, or
simply ll out the warranty registration form on our website. We always keep your information private.
Thank you!
8 Connecting the m905
Okay, let’s get started in making the necessary connections to get your m905 up and running. First
thing to do is mount the m905 in a rack. If you’re not rack mounting the unit, you should attach the
supplied rubber feet on each corner of the bottom cover so you won’t scratch it or the surface you
place it on. If you are installing the ACU in a rack, use the supplied rack screws and nylon washers which
prevent the rack ears from getting marred. The ACU will not run terribly hot, so it can be mounted with
other gear directly above or below. However, you should avoid mounting equipment that can radiate
noise near the m905 (ie power amp, power conditioners, etc).
POWER CONNECTIONS
The m905 ACU has a built-in universal power supply which accepts line voltages of 100 to
240VAC. We include power cable specied for the country where it was ordered, so it
should be supplied correctly. If not, please contact your dealer or distributor for help. For
safety, it is recommended that the AC power cable be connected to a grounded outlet.
POWER-UP SEQUENCE
8
Before powering up your m905, make sure your monitor speakers or power amps connected to your
monitors are turned OFF. Once the m905 and the rest of your audio system are powered up, turn on the
power to your speakers. When powering down, we recommend that you rst power o your speaker
system and then power down the m905.
SYSTEM CONNECTIONS
The m905 input, output and interface connections are detailed here. Pinout diagrams for various connectors are located in the cable and connector wiring diagrams (page 41) section of this manual. If you
have an m905 Analog system, all digital inputs, digital loop thru outputs and wordclock will be unavailable.
UNBALANCED ANALOG INPUT This stereo input is for interfacing with consumer level (-10dBv) unbalanced
analog sources. Connections are made using standard RCA cables.
BALANCED ANALOG INPUT The balanced stereo analog input is via female XLR. Connections are made us-
ing standard balanced XLR cables, wired to the pin 1 shield, pin 2 positive, pin 3 negative.
CUE ANALOG INPUT The balanced stereo analog CUE input is via female XLR. Connections are made using
standard balanced XLR cables, wired pin 1 shield, pin 2 positive, pin 3 negative.
TALKBACK MIC INPUT A standard microphone input which can be used with dynamic or condenser mi-
crophones. Phantom power (+48V) is available (see Setup Mode). Wired pin 1 shield, pin 2 positive, pin 3
negative.
AES3 DIGITAL INPUTS 1 & 2 Two stereo AES3 inputs are provided via female XLR connectors. Each of these
conforms to the AES3 standard. In AES Dual Wire mode, the AES1 input is used for the left channel and
the AES2 input is used for the right channel. Note that AES Dual Wire mode requires moving a jumper on
the m905 digital PCBA inside the unit. See AES DW Setup in section 9 of this manual for details. Use of a
high quality 110 Ohm balanced cable is recommended.
S/PDIF COAXIAL INPUT Standard coaxial stereo digital input. The input impedance is 75 Ohms. Use of a
high quality 75 Ohm cable is recommended.
TOSLINK INPUT Standard stereo optical input connector for use with consumer devices. Use a standard
TOSLINK optical cable for connections to this input.
ADAT INPUT This input accepts a standard 8 channel ADAT optical input. 44.1kHz - 192kHz sample rates
are supported (S/MUX for 96kHz-192kHz). The user can select any of the four channel pairs for monitoring.
Use a standard optical / LIGHTPIPE cable for connections to this input.
USB CLASS 2 AUDIO INTEFACE. USB input for streaming audio to and from a host computer. Use a standard
USB type A -to- type B cable (included with your m905). The type A connector is to be plugged in to the
HOST computer and the type B connector to the m905 input. PCM 44.1kHz – 192kHz/24 bit and DSD (64x
2.8224MHz via DoP V1.1) are supported. Please refer to ‘computer audio setup’ for further details about
using this input.
SPEAKER OUT 1 / 2 / 3 Balanced stereo analog speaker outputs are provided via male XLR connectors,
which connect to your stereo monitor systems (power amps or powered speakers). Connections are
made with standard balanced XLR cables. These inputs are wired to the pin 1 shield, pin 2 positive pin 3
negative. Note: See the unbalanced termination wiring diagram for connecting any of these outputs to
unbalanced equipment. (p.37)
CUE OUTPUT A balanced stereo CUE output is provided via male XLR connectors. Normally, this output is
fed by the CUE input signal and would typically be wired to your studio’s headphone cue system. Connections are made with standard balanced XLR cables. These inputs are wired pin 1 shield, pin 2 positive pin 3
negative. Note: See the unbalanced termination wiring diagram for connecting these outputs to unbal-
9
anced equipment. (p.37)
SUB / DAC / METER OUTPUT Meter OUTPUT – Can be congured as either two mono balanced subwoofer
outputs, one stereo subwoofer output, a stereo balanced xed DAC output, or a stereo balanced congurable meter output.. These output options are congurable in the setup menu. Subwoofer outputs
settings are congured with each speaker output. As a DAC out, the last selected digital input is converted
and sent to this output at all times. Typically this output is used to utilize the high performance m905 DAC
when connected to an analog mastering deck or other analog outboard gear. The meter output can be
congured at a xed level or to follow the speaker monitoring level. Connections are made with standard
balanced XLR cables. Connectors are wired pin 1 shield, pin 2 positive pin 3 negative.
STEREO HEADPHONE OUTPUTS HEADPHONE outputs are provided via ¼” TRS (Tip, Ring, Sleeve) jacks, one
on the frontpanel of the ACU and the other on the RCU (RCU cable upgrade required for m905 Analog units).
These outputs are wired in parallel. The headphone output amplier is capable of delivering very high currents to the headphones and can drive loads down to 25 Ohms.
DIGITAL OUTPUTS AES3, S/PDIF Two stereo digital (loop-thru) outputs are provided via AES3 XLR and S/
PDIF RCA connectors. These provide a buered output of a user selectable digital input. Use of high quality 110 Ohm balanced cable for the AES3 out 75 Ohm cable for the S/PDIF out is highly recommended.
WORDCLOCK IN The m905 can accept a Word Clock signal from an external clock generating unit via this
BNC connector. This might be a stand-alone clock source or via, for example, the Word Clock output from
your digital audio workstation. It should be noted that referencing the m905 from an external Word Clock
is not necessary for the unit to function properly as the m905 will also function very well by stripping
embedded clock data from a connected digital audio source. However, you may have your entire digital
audio system referenced from a single master clock, hence the ability for the m905 to receive and lock
itself to this clock.
WORDCLOCK OUT The Word Clock output allows the user to synchronize other digital audio equipment to
the m905. It functions in two modes: When monitoring a digital input with the clock source set to “word
clock” the word clock output will be a buered copy of the word clock input. If the input being monitored
is not set to have word clock as the clock source then the word clock output will be the clock recovered
from the the incoming digital audio data stream. In the case of USB the word clock output will be derived
from the m905 internal clock. The output is buered and is designed to drive a 75 Ohm line.
WORD CLOCK LOAD SWITCH The switch labeled 1M Ohm/75 Ohm is used to terminate the Word Clock
input. If the Word Clock signal in your studio is being daisy-chained from unit to unit (including the m905),
you’ll want to set the switch to 1M Ohm, which is essentially an unloaded setting. If the m905 is the only
device being clock referenced (or the last unit in a daisy-chain of other high impedance units), you’ll want
to select the 75 Ohm load position for proper termination. NOTE: Selecting the 75 Ohm load position when
there is already another device on the line that has a 75 Ohm load will create a total load of 37 Ohms, which
will attenuate the signal to a point where the m905 may not lock.
REMOTE CONNECTOR The m905 RCU handles all system control. Connection to the m905 RCU is via this
DB15 connector, which carries RS422 serial data, DC power and headphone signals. The m905 ships with
a high quality 25’ cable. While the serial data can travel over 1000 feet we do not recommend cables
longer than 50’ for headphone use. Be sure to use the supplied DB15 cable. If you need a longer, cable
contact your Grace Design dealer or us directly. Do not use an o the shelf DB15 cable as the pinout will
be incompatable. Important Note: The m905 Analog ships with a standard ethernet cable for connecting
the RCU. This cable does not carry the headphone signal to the RCU, so the headphone jack on the RCU will be
deactivated and a small jack plug will be installed. If you wish to use the headphone jack on the RCU, a cable
upgrade is available for purchase from your Grace Design Dealer or directly from the Grace Design Factory.
TALKBACK SWITCH The talkback switch input allows the connection of an external switch, such as a
footswitch, for remotely activating the talkback mic input, or the built in talkback mic on the RCU. The
input is a TRS jack and is used with a “normally open” switching device. Note that when using this jack the
10
talkback function can be activated at both the RCU and the remote switch. See the remote talkback cable
diagram at the end of this manual for connection details.
9 Normal Operation Mode
m905 operation is categorized in two dierent modes: normal operation mode and setup mode. Once
the RCU and ACU are connected and power is turned on, the system boots up into normal operation
mode.
In normal operation mode, all of the ACU controls are active and the LCD display shows the main operating screen with input, level, SPL and DAC status. Setup mode is entered by pushing the ‘setup’ button,
which switches the LCD display to the setup menu. Upon entering setup mode, current monitoring
function is preserved, but the display and controls will be dedicated to setup menu navigation and
input.
The m905 is a closed loop control system to ensure that the status reported on the RCU matches the actual hardware setting in the ACU. Any changes made to the conguration of the system are transmitted
to the ACU where they are processed and reported back to the RCU for conrmation. In the following
sections all of the controls and features of the normal operation mode are detailed.
INPUT SELECTION
The RCU features 8 dedicated input select buttons, in 2 rows of 4, above and below the LCD display. The
m905 Analog has 4 dedicated input select buttons along the bottom of the LCD display. Pressing any
of these buttons will select the associated input source and connect it to the main monitor path. The
currently selected input source is indicated by the blue input icon on the LCD, while inactive inputs
are indicated by the gray input icons. NOTE: The displayed name is user congurable in setup mode. The
names used here are the defaults.
UNBALANCED Selects the unbalanced analog input for the monitoring path.
BALANCED Selects the balanced analog input for the monitoring path.
BALANCED 2 (m905 Analog only) Selects the second balanced analog input for the monitoring path.
CUE Selects the balanced cue analog input for the monitoring path.
TOSLINK Selects the TOSLINK digital input for the monitoring and DAC path.
ADAT / AES DW When ADAT mode is active - Selects the ADAT digital input for the monitoring and DAC
path. Once selected, pressing the ADAT input button again increments sequentially through the channel
pairs (1-2, 3-4. 5-6, 7-8 for regular ADAT and 1-2, 3-4 for S/MUX ADAT ). When AES Dual Wire mode is active
(congured in SETUP), selects the AES Dual Wire input for monitoring and DAC path. Note that AES Dual
Wire mode requires moving a jumper on the m905 digital PCBA inside the unit. See AES DW Setup in section 9 of this manual for details.
S/PDIF Selects the S/PDIF digital input for the monitoring and DAC path.
AES1 / AES2 Selects the AES1 or AES2 digital input for the monitoring and DAC path. Once selected,
pressing the AES input button again toggles the AES1 or AES2 selection. The system remembers the last
AES input that was selected (as indicated by the input icon display).
USB Selects the USB digital input for the monitoring and DAC path.
VOLUME CONTROL, PRESET & HEADPHONE MUTE
11
The m905 utilizes a single rotary pushbutton encoder for control of the speaker and headphone volume
levels, level preset recall and headphone mute. Switching between speaker level and headphone
level control is done by pushing and releasing the volume control knob. The current volume levels are
indicated on the display with the active control being green and the inactive control in light gray. The
volume control is speed sensitive, so the turning the knob at a higher velocity results in faster volume
changes.
<figure - Level display>
WITH SPEAKER CONTROL ACTIVE:
• Clockwise rotation of knob increases volume in 0.5dB increments (max level = 100 in standard display
mode and is user configurable in reference level display mode).
• Counter-clockwise rotation of knob: Decreases the volume in 0.5dB increments (min level = 0).
• Press + hold knob: Recalls global speaker output preset level (configured in SETUP).
WITH HEADPHONE CONTROL ACTIVE:
• Clockwise rotation of knob: Increases volume in 0.5dB increments (max level = 100).
• Counter-clockwise rotation of knob: Decreases the volume in 0.5dB increments (min level = 0).
• Press + Hold knob: If the headphone level is 0.0, press and hold will recall the headphone preset level
(configured in SETUP).
• If the headphone level is greater than 0.0, press and hold will mute the headphone output. This state is
indicated by the headphone mute icon on the display.
SPEAKER OUTPUT SELECTION
The speaker output selection is accomplished using the three illuminated ‘speaker’ push button switch-
es. The active speaker output is indicated by its switch illuminated green, while inactive outputs are not
illuminated. The user dened name (congured in SETUP) is also visible on the display.
SPEAKER 1 Selects the speaker 1 output monitoring path, selects the speaker 1 sub (congured in SETUP)
and mutes speaker 2 and 3
SPEAKER 2 Selects the speaker 2 output monitoring path, selects the speaker 2 sub (congured in SETUP)
and mutes speaker 1 and 3
SPEAKER 3 Selects the speaker 3 output monitoring path, selects the speaker 3 sub (congured in SETUP)
and mutes speaker 1 and 2.
MONITORING OPTION CONTROLS
MUTE / SOLO The multi-function MUTE / (solo) button controls speaker MUTE and monitor path SOLO
features.
Speaker MUTE mutes the signal going to the selected speaker and sub (if assigned) output(s). When
the speaker MUTE is active, the switch is lit solid red and the speaker MUTE icon is shown on the speaker
status display.
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SOLO mode provides a means to monitor left or right channel program material exclusively. When SOLO
mode is active, the button ashes red. The active SOLO channel is indicated on the speaker and headphone status display. In left channel SOLO mode, the right channel is muted in the speaker and headphone outputs.* In right channel SOLO mode, the left channel is muted in the speaker and headphone
outputs.* (NOTE: Enabling MONO during SOLO mode routes the active solo channel to both left and
right outputs.
* The operation of the sub output in SOLO mode depends on the selected sub conguration. In L + R stereo
sub mode, the left and right solo feature is available and follows the speaker / headphone solo. For any other
sub conguration, the sub output mutes when SOLO is active.
PRESS AND RELEASE BUTTON:
• Toggles the speaker output mute on and off (if solo mode is off ).
• Disables speaker / headphone solo if solo mode was active.
PRESS AND HOLD BUTTON:
• Enables the solo mode if solo mode was inactive. The last used solo mode (left or right) is activated upon
entering solo mode.
• Toggles the left / right channel solo mode if solo mode is already active.
SUB MUTE / subsolo) - The multi-function SUB MUTE / (sub-solo) button controls the sub-mute and sub
-solo features. NOTE: These features are only available when the SUB/DAC/METER is congured for sub output
mode in SETUP.
SUB-MUTE mode mutes the signal going to the sub output (if assigned). When the SUB-MUTE is active,
the switch is lit solid red.
Sub-solo mode provides a means to monitor the sub output program material exclusively. In Sub-solo
mode, the speaker output is muted and only the sub output is on. When Sub-solo mode is active, the
button ashes red.
PRESS AND RELEASE BUTTON:
• Toggles the sub output mute on and off (if sub-solo is disabled).
• Disables sub-solo if sub-solo mode was active.
PRESS AND HOLD BUTTON:
• Toggles sub-solo mode on and off.
DIM / xfeed) - The multi-function DIM / (x-feed) button controls the speaker DIM and headphone x-feed
features.
Speaker DIM attenuates the speaker and sub (if assigned) by the preset attenuation level congured in
SETUP. When speaker dim is active, the switch is lit solid yellow.
Headphone x-feed engages the cross-feed circuit in the headphone output. When x-feed is active it is
indicated on the headphone status display. X-feed (cross-feed) simulates the acoustics of a loudspeaker
listening environment which can signicantly improve imaging while reducing listening fatigue when
using headphones. This feature employs carefully designed signal cross-feed, ltering and delay circuits
to simulate hrtf (head related transfer functions).
PRESS AND RELEASE BUTTON:
• Toggles the speaker DIM function on and off.
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