m201
microphone preamplifier
optional A/D converter module
owner’s manual
manual Rev D
all contents ©2007 Grace Design/ Lunatec LLC
Important Safety Information
GENERAL
•Indoor use only
•Ordinary Protection: This equipment should not be exposed to dripping or splasing.
•Avoid placing objects filled with liquids, such as vases or glasses, on this equipment.
•Class I Equipment (grounded type)
•Electrical rating: 100-120/220/230-240V~ 50-60Hz 30W
•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: preamplifier - 7.5kg (16.5lbs)
SAFETY MARKING SYMBOLS
CAUTION: READ ACCOMPANYING DOCUMENTS
This symbol, located on the equipment and in this manual, refers to impor-
tant instructions. Read this manual thoroughly before operating this equip-
ment.
WARNING: ELECTRICAL SHOCK HAZARD
This symbol, located on the equipment and in this manual, indicates the
potential for electrical shock hazard.
SERVICE INFORMATION
The Grace Design m201 contains no user serviceable components. Contact Grace Design
for repair and upgrade information. In the event that your Grace Design m201 needs to be
returned to the factory, contact us for a return authorization number.
grace design m201
owner’s manual
3
Front Panel Controls
A
C
B
1
2
40
40
50m
50s
m201microphone preamplifier
48V
ribbon
48V
ribbon
30
50
30
50
(
)
(
)
+10dB
+10dB
HI-Z
HI-Z
130V
130V
70m
30s
30m
70s
20
60
20
60
INPUT MODE
INPUT MODE
100m
M+S WIDTH
+48V
- 20dB
HI-Z
+48V
- 20dB
HI-Z
GRACE DESIGN USA
H
D
F
G
I
E
of the music signal at the input of the preamplifier.
The switch illuminates green and provides power for
a sealed gold contact relay located on the preamplifier
circuit board. This eliminates signal wiring to the front
panel and switch contact performance problems. The
polarity reverse function is active for all input connec-
tors.
A
switch
24 position gold contact gain
Each gain control has 24 positions and adjusts the volt-
age gain from 18dB to 64dB in 2dB steps. In ribbon
mode the gain range is 28dB to 74dB in 2dB steps.
B
bi-color LED peak indicator
The LED peak indicator, which monitors the output sig-
nal level, turns green at -14dB and switches to red at
+16dB (12dB before clipping). The threshold level for
peak indication is adjustable on each channel (see the
calibration section of this manual).
F
-20dB pad switch
The 20dB attenuator switch attenuates the input signal
20dB. The switch illuminates amber when engaged.
Like the phase reverse switch, this switch controls a
sealed gold contact relay on the preamplifier circuit
board. With the -20 switch engaged, the effective gain
range becomes -2dB to 44dB. The 20dB attenuator is
active for 48V Phantom, ribbon and (optional) DPA in-
puts. It does not affect the HI-Z inputs.
C
input mode switch
The input mode switch is used to select between the
various types of inputs available with the m201, includ-
ing standard 48V, ribbon mic mode, HI-Z, or the optional
130V DPA™ inputs. Refer to the m201 block diagram at
the end of this manual for signal routing details.
G
HI-Z input
This 1/4 inch TRS input is active when the input mode
switch is in the HI-Z position. Suitable for any high
impedance source such as: bass guitar, acoustic guitar,
electric guitar, keyboards, etc... This input is can be used
balanced with a TRS connector or unbalanced with a TS
connector.
D
48V phantom power switch
The phantom power switch (labeled +48V) connects
the +48V power supply to pins 2 and 3 on the XLR in-
put connector. This switch illuminates red. It should be
noted that the LED in this switch actually monitors the
phantom power voltage at the input. With no micro-
phone connected, the LED will continue to illuminate
for approximately 10 seconds after the phantom power
is turned off as the filter capacitors discharge. As well,
even if the phantom power is switched off, the LED will
illuminate if voltage is being fed from an external source.
(i.e. when using a direct split in a remote recording ap-
plication.) Also, the +48V switch is used to activate the
+130V DPA™ mic power if this option is installed.
H
M-S width control
This knob controls the ratio between the Mid and Side
signals in an M-S recording setup. Please see the ‘pre-
amplifier operation’ section of this manual for complete
information regarding this feature.
I
standby switch
Connects the mains voltage and turns on the m201
When depressed the pushbutton will illuminate green
and the preamplifier will be on. When released the pre-
amplifier will be in standby mode.
E
polarity reversal switch
The polarity reverse switch reverses the absolute phase
grace design m201
owner’s manual
4
Rear Panel Connections
E
WORD/LOOP CLOCK
PUSH
PUSH
MIC IN
130V
2
1
PUSH
PUSH
m201microphone preamplifier
IN
4
1
4
1
S/PDIF
2
3
2
3
TOSLINK
LINE IN
OUT
AES3 OUT
LEAD FREE
M+S OUT
2
1
PUSH
PUSH
Pb
RoHS
COMPLIENT
GRACE DESIGN USA
RIGHT
LEFT
OUT
OUT
MIC IN
OUT
OUT
MIC IN
A
C
D
B
A
XLR mic input connectors
Input connections are made via female XLR connectors
with pin 2 positive, pin 3 negative and pin 1 ground.
48V phantom power is supplied on pins 2 and 3.
B
XLR output connectors
Parallel XLR outputs are provided for sending line sig-
nals to two seperate recording devices or mixers. Out-
put connections are made via male XLR connectors
with pin 2 positive, pin 3 negative and pin 1 ground.
C
M-S XLR output connectors
XLR outputs are provided for sending M-S signals in-
dependently of the standard line outputs. Output con-
nections are made via male XLR connectors with pin 2
positive, pin 3 negative and pin 1 ground.
D
IEC AC power input
Accomodates the included 3 prong AC cable. Connect
to grounded outlet only.
E
130V DPA microphone inputs (op-
tional)
Accomodates 130V DPA© microphones via 4 pin XLR
connectors.
F
Optional A/D Converter module
Optional A/D converter module for the m201 includes
seperate balanced analog A/D line inputs, 2x AES3 out-
puts (single and dual wire), word clock/ loop sync in
and out, S/PDIF out and TOSLINK optical out.
grace design m201
owner’s manual
5
Audio Connections
Microphone input connections are made via female XLR connectors with pin 2 posi-
tive, pin 3 negative and pin 1 ground. 48V phantom power is supplied on pins 2 and
3. Output connections are made via male XLR connectors with pin 2 positive, pin 3
negative and pin 1 ground. If the output is to be used unbalanced, pin 1 should be
connected to signal ground and pin 2 to signal hot. Due to the nature of the balanced
output stage, pin 3 should be left open for unbalanced operation. See <figure 1> below.
Note: This will provide a signal of positive absolute polarity when the preamplifier is being
used with a microphone which produces a positive voltage on pin 2 with positive air pres-
sure on the front of the diaphragm. While a vast majority of microphones conform to this
standard a few do not. Use the phase reverse switch to compensate if necessary.
HOT
1
GND
2
SHIELD
3
(open)
<figure 1> - Unbalanced output cable termination
To connect to the front panel HI-Z input, the input mode selector switch must be
positioned in the “HI-Z” location, which changes the preamplifier input source from
the mic input connector to the front panel TRS jack. The input impedance of the in-
strument input is 2M Ohm (balanced) and 1M Ohm (unbalanced), which is ideal for
inserting high impedance sources such as guitars with passive pickups as well as any
instrument with a high level output. Wiring of the HI-Z jack is Tip positive, Ring nega-
tive, and Sleeve ground. Please note that the gain range of the preamplifier when us-
ing the instrument input is –2dB to +48dB in 2dB steps.
Power Connections
A standard three prong AC power cable is included with the m201. For
safety, the power supply cord must be connected to a grounded outlet.
The Disconnect Device for the m201 is the Mains plug or the Appliance
Coupler on the power supply cord. The Disconnect Device must remain
accessible and operable
AC input voltage settings can be adjusted for 100V, 120V, 220V and 240V operation at
50-60Hz. If your line Voltage is 230VAC then use the 240V setting. From the rear of the
m201, open the trap door next to the IEC power inlet with a small screwdriver. Care-
fully pull the voltage select cam straight out and then insert with the desired voltage
grace design m201
owner’s manual
6
showing. Do not try to rotate the cam while it is in the power input module. Replace
the fuses with the proper value selected from <figure 2> below. Be sure to use a time
delay fuse with a 250V rating.
CAM SETTING
100V~
120V~
LINE VOLTAGE
100V~
120V~
FUSE VALUE
250V~ T 500mA L
250V~ T 500mA L
250V~ T 315mA L
250V~ T 315mA L
250V~T 315mA L
220V~
240V~
240V~
220V~
230V~
240V~
<figure 2 - fuse value table>
CHECK LINE VOLTAGE SETTINGS
Your m201 has been set from the factory to operate at the voltage required for your
part of the world. However, it’s important to double-check this in order to ensure no
damage will come to the unit if power is applied while the setting is incorrect.
Preamplifier Operation
TURNING THE POWER ON
The power switch is located on the m201 front panel. Pushing the power switch in
turns the mains power on (switch illuminates green). Pushing the power switch again
turns the mains power off.
USING THE INPUT MODE SELECTOR SWITCH
The input mode switch to the right of the gain control provides a convenient way for
the user to select between the various types of inputs the m201 can accommodate.
The following in an overview of the four settings:
48V This setting should be selected for all general recording applications with most
microphone types. In this position, the main XLR mic inputs are feeding the preampli-
fier and the dual XLR outputs are active. Proceed with the ‘setting the gain’ discussion
below.
HI-Z This setting is used to select the front panel mounted 1/4” instrument DI inputs.
These inputs can accommodate a wide variety of high impedance input sources, in-
cluding bass guitar, keyboards, electric guitars etc... In this mode, the rear panel XLR
inputs are not active, while the dual balanced XLR outputs carry the amplified signal
from the DI inputs. There is no 48V phantom available on this input. The phase reverse
switch is active, and the gain range of this input is -2dB to +44dB (20dB less than the
48V input), so therefor the -20dB pad is not available. This connector is balanced with
the Tip positive, Ring negative and Sleeve ground.
grace design m201
owner’s manual
7
ribbon This setting puts the m201 into ‘ribbon mic mode’, which is described in detail
below. Use this input for ribbon microphones or any application where an additional
10dB of gain may be required. In this position, the main XLR mic inputs are feeding the
preamplifier and the dual XLR outputs are active.
130V This setting activates the optional 130V input module for DPA microphones. If
the 130V input option is present, this selection will deactivate the standard XLR inputs
and enable the dedicated 4 pin 130V XLR inputs. In this mode, the 48V pushbutton
switch will turn on the 130V power supply. Phase reverse and -20dB pad are available
in this mode. The dual balanced XLR outputs carry the output signal.
SETTING THE GAIN
First, turn the gain control fully counter-clockwise and check that the 48V phantom
power is off. Connect a microphone and then turn on the phantom power if required.
When sending a signal to a recorder, converter or interface that has fixed input levels,
simply increase the gain until the optimum recording level is reached. If the peak in-
dicator flashes red excessively with the gain control in the fully counterclockwise posi-
tion, engage the -20dB attenuator.
When sending a signal to a tape recorder with an input attenuator (i.e. the record level
control on a DAT or CDR recorder) use the following procedure: With the sound source
present, turn the gain control clockwise until the peak LED begins flashing red, then
reduce the gain until the red stops flashing. Since red indicates a peak level which is
12dB before preamplifier clipping (6dB in unbalanced mode), it is OK for it to come on
periodically during recording. If peak indicator flashes red excessively with the gain
control in the fully counterclockwise position, engage the -20dB attenuator. Now ad-
just the recorder input control for the optimum recording level.
Ribbon Mic Mode
Selecting the ribbon mic position on the input mode switch optimizes the channel for
ribbon microphones by boosting the gain by 10dB while disabling 48V phantom pow-
er and optimizing the mic input impedance. Before activating ribbon mic mode, make
sure the channel’s gain is fully down (counter-clockwise) and 48V phantom power is
off. Now simply select ‘ribbon’ input mode and turn the gain control upwards until the
proper recording level is achieved.
If you press the 48V phantom switch while the ribbon switch is engaged, the mic pow-
er will not turn on. However, if the 48V phamtom switch remains depressed and the
input mode switch becomes inadvertently changed to ‘48V’, 48V phantom will conse-
quently be activated, which can potentially harm a ribbon your microphone if it is still
connected to the input. If the 48V phantom power switch is turned of and then the
ribbon mode is selected, the preamplifier will wait until the phantom power voltage
grace design m201
owner’s manual
8
has completely discharged and then the ribbon mode will activate automatically.
An additional benefit of the ribbon mic mode is that the input DC blocking capacitors
are relay bypassed to further simplify the m201’s signal path. Incidentally, the ribbon
mode works very well with many lower output dynamic microphones as well as ribbon
types.
M-S recording with the m201
In M-S mode the m201 accepts the Mid signal in channel 1 and the Side signal in chan-
nel 2. The LEFT channel output connector provides the “sum” of the inputs and the
RIGHT channel output connector provides the “difference” of the inputs. In M-S mode,
the M-S width control adjust the ratio of Mid signal to Side signal in the dedicated M-S
outputs. The LEFT and RIGHT M-S outputs are always active which allows the user to
record the discreet Mid and Side signals from the preamplifier Channel 1 and 2 out-
puts while also recording (or monitoring) the stereo composite from the M-S LEFT and
RIGHT outputs.
Note: For more information on M-S recording we would highly recommend the AES
paper written by Wes Dooley and Don Streicher called “M-S Stereo: A Powerful Tech-
nique for Working in Stereo”. This paper (No. 1792) is available from the Audio Engi-
neering Society web page (www.aes.org).
The Optional A/D Converter Features
A
C
B
FS SELECT
CLOCK SOURCE
ADC MODE
44 48 88 96 176 192
OFF
INT WORD LOOP
PRO 2WIRE CONS
sLOCK
OVER
0
1
J
I
-60 -50 -40 -32 -28 -24 -20 -18 -16 -14 -12 -10 -8 -6 -5 -4 -3 -2 -1
D
2
14 16 18 20
HEADROOM dB
-0.4 -0.3 -0.2 -0.1
0
0.1 0.2 0.3 0.4
<
>
OVER
(
)
CAL
LEVEL
CH1-2 MS LINE
A
B
/ MODE
(hold)
PEAKRESET
INPUT SENS
ADC SOURCE
H
G
F
E
grace design m201
owner’s manual
9
A
FS SELECT this switch is used to toggle through the available ADC sampling rates
CLOCK SOURCE this switch is used to select the ADC clock source
B
C
ADC MODE this switch is used to select single or dual wire AES,
and switch between either professional or consumer fomat
D
OVER lights illuminate when the ADC has been overload-
ed, and remain lit until the PEAK RESET swich is pushed
E
PEAK RESET / MODE This switch is used to clear peaks on the 20 seg-
ment led meter and to select how the meters display peak information.
F
INPUT SENSITIVITY CALIBRATION SCALE
G
INPUT SENS selects between the two program-
mable ADC input sensitivity settings.
H
I
ADC SOURCE selects the input source which feeds the ADC module
ADC headroom indicator
J
20 segment LED level meter
Operating The A/D Converter Module
If you have purchased the optional A/D (analog to digital) converter module for
your m201, the following section will help you become familiar with its features and
its operation. The m201 A/D card is available installed on new m201’s from the fac-
tory, or as an upgrade to your existing m201. If you need more information about up-
grading your m201 with the A/D module, please feel free to call us at 303.443.7454.
INPUT SOURCE SELECT The m201 A/D can receive signals from 3 different in-
puts: channels 1&2 from the mic preamplifier section, the M-S matrix outputs, or the
external balanced line inputs (located on the back panel of the A/D module). The A/D
source select switch (lower left) is used to toggle between the three input source op-
tions, which are illuminated green directly above in the bezel. Simply push the button
to select the input source you require.
FS SELECT The m201 A/D converter can operate at sampling rates of 44.1, 48,88.2,
96, 176.4, and192kHz. Whether operating on the internal crystal or an external clock
source, you must select the appropriate sampling rate you wish to record at. The
top left switch above the A/D bezel labeled FS SELECT is used to toggle between
grace design m201
owner’s manual
10
all the available sampling rates. Simply push the button to select the sampling
rate you require. The selected rate will be illuminated green below. Selecting “OFF”
puts the A/D converter circuitry in low power standby mode with all oscillators off.
CLOCK SOURCE The m201 A/D can be run from the internal crystal, an external word
clock source, or from DigidesignTM loopsync*. The top middle switch, labeled CLOCK
SOURCE, is used to select between these options. The selected clock source will be il-
luminated green below the switch.
A/D MODE The m201 A/D is capable of transmitting AES/EBU digital audio in sin-
gle or dual wire modes, and in either professional or consumer format. The upper left
switch selects between these various formats. The selected format will be illuminated
green below the switch.
PEAK RESET / MODE High resolution 20 segment metering is included with the
m201 A/D option. When A/D input signals hit or exceed absolute zero (0dBfs), the over
indicator lights (‘over’ placed above and below ‘0’ on the meter) will illuminate red and
remain lit until the peak reset switch is pushed.
Peak signal levels are indicated by the highest level LED remaining lit. The peak in-
dicators can programmed to remain lit indefinitely until the reset switch is pressed
(infinite); stay lit for 4 seconds (delay); or not stay lit at all (off). These three modes are
selected by simply pressing and holding the PEAK RESET / MODE switch for approxi-
mately 3 seconds, which toggles through the three available modes.
A/D Converter Sensitivity
The m201 A/D converter features two independent A/D sensitivity configurations. The
front panel interface allows the user to easily switch between these two calibrated set-
tings. Each of the two input sensitivity ranges (A) and (B) can be configured for one of
four standard A/D sensitivities.The following sections detail the operation and calibra-
tion of this feature.
SELECTING THE A/D SENSITIVITY From the m201 front panel interface, pressing
and releasing the INPUT SENS push button toggles the selected A/D input sensitivity.
The currently selected range (A) or (B) is illuminated.
CALIBRATING THE A/D SENSITIVITY The m201 ships with the following two de-
fault sensitivity calibrations: (A)+22dBu = 0dBFS (18dB Headroom) (B)+18dBu =
0dBFS (14dB Headroom). Internal trim controls allow you to reconfigure either (or
both) of the sensitivity levels. Four standard sensitivities are supported in the m201
A/D converter: +18dBu = 0dBFS (14dB Headroom) +20dBu = 0dBFS (16dB Headroom)
+22dBu = 0dBFS (18dB Headroom) +24dBu = 0dBFS (20dB Headroom).
grace design m201
owner’s manual
11
The front panel interface features a calibration mode that allows precise adjustment of
the A/D sensitivity. To recalibrate one or both of the input sensitivity configurations,
simply do the following:
1) Disconnect AC power from the m201.
2) Remove the 8 top cover screws using a #2 Phillips screwdriver. Lift the top cover
off the unit and set it aside.
3) Reconnect AC power to the m201 and turn it on.
4) Connect a signal generator to the A/D LINE inputs. Set the signal generator output
to +4dBu @ 1kHz (1.29V rms).
5) Turn on the m201 A/D converter and select LINE as the A/D input source.
6) To enter CAL mode, press and hold the INPUT SENS button for approximately 3
seconds. The normal operation displays will extinguish and the CAL indicator will
begin flashing indicating CAL mode is active. The current input sensitivity range
(A) or (B) will be illuminated along with that range’s current sensitivity calibration
(shown as “dB Headroom” in the bottom left of the meter display).
7) Press and release the INPUT SENS button to select the range (A) or (B) that you
wish to calibrate.
8) Press and release the A/D SOURCE button to scroll through the 4 available sensi-
tivities until the desired setting is illuminated.
In calibration mode, the digital audio meter is configured such that the “0” position is
the target sensitivity level. The meter then indicates the current signal level versus this
target sensitivity. The meter will display a window centered around the target sensitiv-
ity with a +/- 0.4dB width (in 0.1dB increments). When the sensitivity adjustment on
the A/D converter is calibrated for the selected setting, only the “0” LED will be illumi-
nated. If the signal level is high, the 0 indicator will be illuminated along with the error
(in 0.1dB increments) to the right of 0. If the signal level is low, the 0 indicator will be
illuminated along with the error (in -0.1dB increments) to the left of 0.
On the m201 A/D module, trim pots are used to adjust the (A) and (B) ranges for each
channel. Each of these are labeled on the A/D module circuit board <figure 3>.
9) Locate the appropriate trimmer for the channel you wish to adjust. If the current
signal level is high, you need to decrease the A/D sensitivity. Using a non conduc-
tive tool, turn the appropriate trim pot counter-clockwise to reduce the level until
only the “0” is illuminated on the m201 meter. If the current signal level is low, you
need to increase the A/D sensitivity by turning the appropriate trim pot clockwise
to increase the level until only the “0” is illuminated on the LED level meter.
grace design m201
owner’s manual
12
10) Once all desired calibration adjustments have been made, press and hold the
INPUT SENS button for approximately 3 seconds. This will exit CAL mode and re-
turn the A/D to normal operation. The new settings are now stored until future
changes are made.
11) Power down the unit, disconnect the AC power and reinstall the top cover.
C27
U3
P6
C4
P2
C6
R11
R39
R12
K6
R32
R23
R26
C14
C36
C17 C32
Q3
D6
D5
K5
K4
K3
K2
K1
C15
C25
C11
D7
C41
R22
CH2 (B): VR4
CH1 (B): VR1
D4
1
3
3
1
3
3362
3362
B VR4
A VR3
VR1 B
VR2 A
R38
1
2
1
1
3
3362
3362
D3
CH2 (A): VR3
CH1 (A): VR2
Q2
R13
R19
K7
R31
R29
R10
D2
U9
U5
D1
R16
C40
C21 C31
Q1
C10
TP1 TP2
+15VA
TP3 TP4 TP5 TP6
+18V
R9
J2
-18V -15VA +6.5V +3.3V
C46
P4
J4
U4
P1
C20
P5
C13
C29
U11
P3
C42
FD1
J5
FRONT PANEL
<figure 3 - A/D sensitivity trim pot locations>
grace design m201
owner’s manual
13
Maintenance
The model m201 was designed to be maintenance free for many years. It is highly
unlikely that your unit will require service. However, there are two adjustments that
may need to be made from time to time. These procedures should be made only by a
qualified service technician or at the Grace Design factory.
PEAK LED ADJUSTMENT PROCEDURE
The peak LED threshold levels may be adjusted to a user defined operating level. This
circuit is set at the factory with the green threshold at -14dBu and the red threshold
at +16dBu. The relationship between the two thresholds is fixed. The procedure for
adjusting the greed / red threshold follows:
EQUIPMENT NEEDED
• Sine wave audio signal generator or oscillator output from a mixing console.
• Audio level meter or an RMS Volt meter with dBu or dBm scales
• Plastic alignment tool or small screwdriver
• Appropriate interconnect cables
• #2 phillips head screwdriver
PROCEDURE
1) With the power off, remove the eight phillips head screws from the top cover and
remove it from the m201
2) Set all of the gain controls to the 30dB position
3) Connect the audio generator to the input of channel 1
4) Set the generator output level to approximately -20dBu @1KHz.
5) If the generator has an unbalanced output, refer to figure 2 below for termination
information
6) Connect the level meter to the output of channel 1.
7) If the level meter has an unbalanced input, refer to <figure 1> for unbalanced
output termination information.
8) Apply power to the generator, preamplifier, then the level meter.
9) Adjust the generator output level so that the preamplifier output level is at the
desired red threshold. If the proper level can’t be reached, adjust the preamplifier
gain control.
10) Locate VR2A (VR2B for channel 2) (see <figure 3>) on the channel 1 audio circuit
board and adjust until the peak LED is between green and red. The color should
appear amber when the setting is correct. Repeat this procedure for channel 2.
11) If it is desired to calibrate the peak indicator to a specific converter/recorder
input level, simply connect the output of the preamplifer to the converter/re-
corder. Adjust the signal generator so that the desired peak level is indicated on
the recorder and then adjust VR1 until the peak LED is between green and red.
grace design m201
owner’s manual
14
INPUT OFFSET ADJUSTMENT
The input amplifiers in the m201 are ultra-precision laser trimmed devices which have
a very low input offset. However, even the smallest differential offset at the input can
result in an audible “click” when the gain control is turned. It should be noted that this
type of click will be audible when no signal is present. With no signal present there is
no signal amplitude to be changed unless input offset is present. This procedure nulls
the input offset and minimizes the clicking sound with no signal present. In contrast,
there will almost always be an audible click if turning the gain control while a signal is
present. This is because the gain control, being a stepped control, will make an instan-
taneous change in amplitude when turned, which creates a transient signal.
EQUIPMENT NEEDED
• DC Volt meter with at least 1mV sensitivity
• Plastic alignment tool or a small screwdriver
• #2 phillips head screwdriver
PROCEDURE
1) Remove the 8 phillips head screws from the top lid but leave the lid in place.
2) Set all of the preamplifier gain controls to maximum.
3) Turn on the m201 preamplifier and allow to warm up for at least 45 minutes. (go
get a nice cup of coffee and do some stretches)
4) Remove the top lid and locate the DC offset test points TP1A and TP2A (see figure 4
next page). Place the Volt meter probes into these holes.
5) Locate DC offset potentiometer VR1A (VR1B for channel 2) and rotate it for a read-
ing of 0.000VDC +/- 0.003V.
6) The input offset does drift with temperature and having the lid off will allow the
circuitry to cool. It is advisable to replace the lid and let the preamplifier warm up
again (about 20 minutes) and then re-check your adjustments.
Cleaning
Your m201 preamplifier chassis is constructed out of high quality stainless steel. Under
normal circumstances, virtually no maintenance is required to keep the unit looking
shiny and new. However, if your unit becomes smudged or dirty, here are some clean-
ing tips: We recommend using either Pledge furniture polish or Zep brand stainless
steel cleaner (available at the hardware store). Apply cleaner to a clean, dry, lint free
cloth and gently wipe all stainless surfaces, taking care not to allow the cleaning prod-
uct to build up around the panel switches or knobs.
grace design m201
owner’s manual
15
D
1
A
D
4
A
D
1
B
D
4
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5
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<figure 4 - offset test point and peak LED adjust trim pots>
grace design m201
owner’s manual
16
Specifications
preamplifier specifications (without A/D converter)
Frequency Response
@ 40dB gain ± 0.2dB (50Ω source)
@ 40dB gain ± 3dB (50Ω source)
THD+N
18Hz-65kHz
4.5Hz-350kHz
@ 20dB gain +25dBu out, 1kHz
@ 40dB gain +25dBu out, 1kHz
@ 60dB gain +25dBu out, 1kHz
Intermodulation Distortion
@ 40dB gain +25dBu out
SMPTE/DIN 1:1 (50Hz, 7kHz)
SMPTE/DIN 4:1 (50Hz, 7kHz)
Noise - Referred to Input
@ 60dB gain 50Ω source
@ 60dB gain 150Ω source
@ 60dB gain 600Ω source
Phase Deviation
100Hz-20kHz @40dB gain
Crosstalk
Any Channel @ 40dB gain 1kHz
Any Channel @ 40dB gain 10kHz
CMRR
<.0008%
<.0009%
<.0070%
<.0020%
<.0030%
-130dB
-127dB
-123dB
<3°
-125dB
-115dB
@ 60dB gain, 3.5Vcm, 1kHz
@ 60dB gain, 3.5Vcm, 10kHz
Maximum Output Level
1kHz, 100KΩ load
>70dB
>70dB
+28dBu
Impedance
Input
Input, ribbon mode
Output
8100Ω
20kΩ
190Ω
Peak Led Meter
Green threshold
Red threshold
-14dBu
+16dBu
Weight and Dimensions
dimensions
weight
2U, 19”rack mount x 10” deep
16.5lbs (7.5kg)
Power Consumption
100/120/230/240V~ 50-60Hz
20 Watts Max
A/D module specifications (line input)
Dynamic range
20Hz-20kHz
“A” weighting
>115dB
>117dB
THD+N
1kHz, -1dBFS, 20Hz-22kHz
Frequency response
< 0.00026% (-112dB)
-3dB
+/-0.2dB
44.1kHz Fs
48kHz Fs
5Hz-21kHz
5Hz-23kHz
5Hz-41kHz
5Hz-45kHz
5Hz-54kHz
5Hz-59kHz
22kHz
24kHz
44kHz
48kHz
72.5kHz
79kHz
88.2kHz Fs
96kHz Fs
176.4kHz Fs
192kHz Fs
Full scale input level
+16dB or +24dB (+/-2dB trim)
CMRR
60Hz
1kHz
>65dB
>80dB
>60dB
10kHz
IMD SMPTE 4:1 60Hz, 7kHz, -3dBFS
Interchannel crosstalk
<100dB (0.0008%)
<120dB
Group delay
44.1-48kHz
Sample rates, internal crystal (kHz)
13/Fs
44.1, 48, 88.2, 96, 176.4, 192
External Clock Lock Range
Wide lock mode
s-Lock™ mode
40.1kHz-207kHz (+/-8% at each sample rate)
+/-250ppm (+350, -400ppm typical)
Intrinsic Jitter, 200Hz-20kHz BW
Jitter Rejection Corner Frequency
A/D sensitivity
Wide lock mode
s-Lock™ mode
< 60ps RMS
< 40ps RMS
Wide lock mode, -3dB, 12dB/octave
s-Lock™ mode, -3dB, 12dB/octave
800Hz
10Hz
Range A
Range B
+22dBu = 0dBFS (18dB headroom*)
+18dBu = 0dBFS (14dB headroom*)
*can be calibrated for any setting between +18dBu = 0dBFS and +24dBu = 0dBFS
grace design m201
owner’s manual
17
Signal Flow Diagram
grace design m201
owner’s manual
18
Warranty Information
Grace Design warrants all of our products to be free of defective parts and work-
manship for a period of five years.This warranty period begins at the original date
of purchase and is transferable to any person who may subsequently purchase the
product during this time.
This warranty excludes the following conditions: normal wear and tear, misuse,
customer negligence, accidental damage, unauthorized repair or modification,
cosmetic damage and damage incurred during shipment.
During the time of this warranty, Grace Design will repair or replace, 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 original
factory serial number.
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 the original date of purchase.You may also register
your product directly with Grace Design by telephone (303-443-7454 Monday-
Friday 9:00am to 5:00pm MST), or you can register your product online at www.
gracedesign.com.
This warranty is in lieu of all other warranties whether written, expressed, or
implied, INCLUDING ANY WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
In no event will Grace Design be liable for lost profits or any other incidental,
consequential or Exemplary damages, even if Grace Design is aware of the
possibility of such damages. In no event will Grace Design’s liability exceed the
purchase price of the product
This warranty gives the customer specific legal rights.The customer may also have
other rights, which vary from state to state. Some states do not allow limitations
on implied warranties or consequential damages, so some of the limitations of the
above may not apply to a particular customer.
grace design m201
owner’s manual
19
Manual Revisions
Revision Page Change
Date
Initials
mbg
A
B
B
B
Initial release
04/25/2007
04/26/2007
04/26/2007
04/26/2007
3
4
6
Changed voltage range and power specifications
Power switch description changed to standby switch.
Added power mains disconnect information
mbg
mbg
mbg
B
C
D
13
9-12
7
Added signal flow diagram
04/26/2007
11/08/07
4/24/08
edg
edg
edg
Added A/D module infirmation
changed fuse values for 220V-250V from 250 to 315mA
grace design m201
owner’s manual
20
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