GRACE DESIGN M908 Monitor Controller Instruction Manual

: June 1, 2024
: GRACE DESIGN

Table of Contents

M908 Monitor Controller
ACU
RCU
Signal processing functions
PSU
Signal Processing Specifications
Electrical Specifications
Mechanical Specifications
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m908 Monitor Controller
System Specifications
m908 System Specifications Rev. G
Revision G November, 2023

M908 Monitor Controller

The Grace Design m908 Monitor Controller is designed for monitoring in 7.1, 5.1, stereo, and mono as well as higher channel count playback systems such as Dolby Atmos, Auro-3D, and DTS-X. Up to 24 channel speaker systems can be controlled. The system consists of an Audio Control Unit (ACU), Remote Control Unit (RCU), and Power Supply Unit (PSU). The RCU communicates with the ACU via RS-485 serial connection. The PSU contains dual redundant universal input power supplies which provide the ACU/RCU with DC power for analog and digital circuits.
The m908 standard features include a total of 68 digital input channels, 16 analog output channels, and 24 digital output channels. Up to 16 channels of analog inputs are available with the addition of optional 8 channel ADC modules. The Option I/O module slot provides up to 32 additional digital inputs and outputs. Up to 24 input channels can be received simultaneously and routed to the 24 channel processor. The processor has 24 output channels. The m908 supports sample rates of up to 192kHz at 24bits. Following is an outline of the m908 I/O connections.

ACU

1.1 Input Connector configuration
1.1.1 Analog

(2) 8 Channel balanced: DB25 (optional)
(1) 2 Channel balanced: XLR (optional)
(1) 2 Channel unbalanced: RCA Phono (optional)
(1) 2 Channel unbalanced RIAA phonograph preamp: RCA Phono (optional)
(1) 1 Channel balanced Talkback microphone input w/ 48V mic power: XLR
(1) 1 Channel balanced Talkback input: DB15 (from RCU)

1.1.2 Digital

(3) 8 Channel AES3: DB25
(2) 8 Channel ADAT: Optical
(2) 2 Channel TOSLINK (Uses ADAT connectors): Optical
(1) 2 Channel AES3: XLR
(1) 2 Channel SPDIF: RCA Coaxial
(1) 24 Channel USB 2.0: USB-B (asynchronous mode)
(1) 32 Channel IO Option Module

1.2 Output connector configuration
1.2.1 Analog

(2) 8 Channel CR Speaker balanced: DB25
(1) 8 Channel CR Speaker/4 x 2ch Cue: DB25
(1) 2 Channel CR Speaker balanced: XLR
(1) 1 Channel Talkback balanced: XLR
(2) 2 Channel Headphone: 1/4”TRS (one on RCU)

1.2.2 Digital

(3) 8 Channel AES3 x 4: DB25
(1) 32 Channel IO Option Module Slot

1.3 Other connectors
1.3.1 Option I/O Slot

Dante Option
- 32 Ch In/32 Ch Out 44.1-48kHz
- 32 Ch In/32 Ch Out 88.2-96kHz
- 16ch In/16 Ch Out 176.4-192kHz
Ravenna/AES67 (Merging ZMAN)
- 32 Ch In/32 Ch Out 44.1-192kHz
Digilink Option
- 32 Ch In/32 Ch Out 44.1-192kHz

1.3.2 Clocking

Connectors
- (1) Word Clock in: BNC
- (1) Word Clock through/out: BNC
The m908 can synchronize to a variety of clock sources listed below.
- External Word Clock Input
- Internal Fixed Oscillators
- AES3 Inputs
- SPDIF Input
- ADAT Inputs
- TOSLINK Inputs
- Option I/O Module

1.3.3 Control/Computer IO

Ethernet: RJ45 for web UI control.
RCU: DB15 RS485/GPIO/Headphones
USB Host: USB-A
(3) GPIO on Pin 25 of AES3: DB25
(1) GPIO on Pin 5 of RCU: DB15
External Talkback switch with tally: 1/4″ TRS

RCU

2.1 I/O Connections

Talkback/SPL Microphone, Built in
USB Type A Host connector. User preset backup/restore via USB Mass Storage Class.
RS485 communications and headphone signal from ACU on DB15
Headphone Jack 1/4″ TRS

2.2 Sound Pressure Level Meter

Sound Pressure Level with A weighting, C weighting, or no weighting.
Peak Hold with Fast or Slow averaging

2.3 User interface

480×272 QVGA display, LED dimable back light with adjustable dim levels and dim timer.
24 detent encoder with integrated push-button for level control and parameter configuration
8 user defined input buttons
3 user defined illuminated control room speaker output buttons
3 x 3 speaker Solo/Mute dual color push-button array
3 user defined multi-function dual color push-buttons
Illuminated talkback push button
Illuminated DIM push-button, push-hold for headphone crossfeed on/off
Illuminated MONO push-button, push-hold for L-R function
Illuminated MUTE push-button
Illuminated MON>CUE push-button
Illuminated Setup push-button

Signal processing functions

3.1 Volume Control
3.2 Headphone cross feed
3.3 Bass Management

Crossovers for up to 22.2 speaker systems
Bypass available on High Pass filters
Independent High/Low Pass filter slope settings:
Adjustable crossover frequency.
Adjustable LPF output trim.

3.4 Supported speaker formats

Custom user defined formats up to 24 channels
Atmos up to 14.2.6
Auro-3D up to 13.1
DTS-X up to 14.2.6
Standard surround formats (ie: 5.1, 7.1 9.1)
LCRS
2.1
Stereo 2.0
Mono

3.5 Downmix Formats

7.1 > 5.1
7.1 > 5.1 (Dolby PLII)
7.1 > LCRS
7.1 > LCRS2
7.1 > Lt/Rt
7.1 > Lt/Rt (Dolby PLII)
7.1 > Lo/Ro
5.1 > LCRS
5.1 > LCRS2
5.1 > Lt/Rt
5.1 > Lt/Rt (Dolby PLII)
5.1 > Lo/Ro
LCRS > L/R
LCRS2 > L/R

3.6 Meter Output Routing
3.7 Other

All inputs can be routed to any available output for metering.
Meter feed can be pre or post Input Level cal.
Meter feed can can follow monitoring source or be fixed to a single input.

3.7.1 Inputs

Source summing
- Up to 3 inputs can be summed together
Sync Delay
Level offset
De-emphasis control
System Clock source override

3.7.2 Speakers:

Volume control
MUTE/DIM
MONO and Left minus Right
User assignable MUTE/SOLO control
Global level offset
Channel level offset
Channel Delay
Bass management

3.7.3 Room Correction EQ

12 band parametric EQ per channel for Sub channels
12 band parametric EQ per channel for Speaker channels

3.7.4 CUE Outputs

Up to 8 stereo cue paths
Independent stereo level control on each cue
Assignable talkback routing
Source can be configured for CUE input, Control Room L/R, or downmix

3.7.5 Talkback System

Talkback mic amp gain control for RCU and ACU talkback mics

PSU

Talkback trigger sources:
- RCU Talkback switch
- ACU External Talkback switch
- A, B, or C User definable buttons on RCU
- GPIO 1-4 on ACU
Each talkback trigger source can be assigned to enable a specific talkback mic (ACU and/or RCU) and route it to any or all CUE sends.
Adjustable Talkback DIM for control room monitors
Adjustable Talkback DIM for CUE sends

4.1 Model A140 redundant power supply

2 x 40W SMPS modules.

4.2 AC power input: IEC C14
4.3 DC output to ACU: CPC-8.

Signal Processing Specifications

SIGNAL PROCESSING

SIGNAL PROCESSING

Signal Processing – Room Correction EQ

Monitor Control

Attenuation Range| -inf, -99.5dB to 0dB, 0.5dB steps
DIM Attenuation| -30.0dB to 0.0dB, 0.5dB steps
MONO Sum Law| -9.0dB to 0dB, 0.5dB steps

Speaker System Latency AD in to DA out

Cue System Latency AD in to DA out

Electrical Specifications

DA CONVERTER CONTROL ROOM OUTPUTS Fs=48kHz unless otherwise noted.

DA CONVERTER CONTROL ROOM OUTPUTS Fs=48kHz unless otherwise noted.

A/D CONVERTER OPTION Fs=48kHz unless otherwise noted.

THD+N

A/D CONVERTER OPTION Fs=48kHz unless otherwise noted.

Interchannel crosstalk, 1kHz	-140dB
Interchannel crosstalk, 10kHz	-127dB

Input Impedance
Balanced Input (DB25 or XLR)| 20k Ω
Unbalanced Input| 10k Ω

TALKBACK MIC IN > TALKBACK MIC OUT (ANALOG)

Gain Range	+11, +19-74dB in 1dB steps

HEADPHONE AMPLIFIER

THD+N

RIAA PHONO AMPLIFIER OPTION

GAIN

| LOW GAIN| HIGH GAIN
Gain @1kHz| 40dB| 60dB
Noise
22Hz-22kHz| -90dBu| -71dBu
22-22kHz, A weighting filter| -96dBu| -76dBu
THD+N
1kHz, 5mV IN| <0.0080%|
1kHz, 1mV IN| | <0.040%
SMPTE/DIN Intermodulation Distortion
SMPTE/DIN 4:1 100/2kHz, 5mV IN| <0.004%|
SMPTE/DIN 4:1 100/2kHz, 1mV IN| | <0.03%
Max Input Level
0.1% THD+N| 110mV| 10mV
Sub Sonic Filter
-3dB| 12Hz| 12Hz
RIAA EQ
accuracy| ±0.10dB| ±0.10dB

GPIO

GPIO Inputs	+5V	+3.3V
Input High Voltage level	>3.3V	>2.0V
Input Low Voltage level	<1.5V	<0.8V
Max Input Voltage level	5.5V	3.8V
GPIO Outputs	+5V	+3.3V
Output High Voltage	5.0V	3.3V
Max Output Current	15mA	10mA

Note: GPIO outputs have 330Ω series output resistors.
External ACU Talkback switch input
Switch input pull-up voltage| 3.3V
Switch input pull-up resistance| 10KΩ
Tally output voltage| 5.0V
Tally output resistance| 330Ω

CLOCKING

Supported Sample Rates kHz	44.1, 48, 88.2, 96, 176.4, 192

GENERAL

| Weight|

Dimensions

---|---|---
Audio Control Unit| 6.8lbs (3.2kg)| 19″W x 3.5″ H x 10.9″ L
Remote Control Unit| 2.2lbs (1.0kg)| 10.5″ W x 2.5″ H x 5.1″ L
Power Supply Unit| 2.6lbs (1.2kg)| 8.5″ W x 1.7″ H x 8.2″ L
Power Consumption
90-250V~ 50-60Hz| 50W Max

Mechanical Specifications

7.1 Dimensions
7.1.1 [ACU dimensions drawing] GRACE DESIGN M908 Monitor Controller -
Dimensions 7.1.2 [RCU dimensions drawing]

GRACE DESIGN M908 Monitor Controller - Dimensions 1 7.1.3 [PSU dimensions drawing] GRACE DESIGN M908
Monitor Controller - Dimensions 2 7.2 Document Revisions

Rev.

| Description| Date|

Initials

---|---|---|---
A| Initial preliminary release| 05/20/19| MBG
B| Correct Ext. Talkback mic gain range Correct firmware version| 10/21/19| MBG
C| Correct ADC Input sensitivity| 10/24/19| MBG
D| Update Room EQ Q range
Update System and Cue Latency specifications| 10/28/19| MBG
E| Update power consumption specification| 11/13/19| MBG
F| Add Wordclock Polarity specification Updated specifications for 1.0.7 Firmware Removed Ross Bach Liberty option| 03/25/21| MBG
G| Updated Dante channel count for 64ch Brooklyn module. Updated number of EQ bands per channel to 12. Updated speaker delay increment to 0.01ms. Updated crossover frequency range. Added high and low shelf slope parameter and range.| 11/17/23| MBG