Grace M201 User Manual 2

m201

microphone preamplifier

optional A/D converter module

manual Rev D

owner’s manual

all contents ©2007 Grace Design/ Lunatec LLC

Welcome

Thank you for purchasing the Grace Design m201 microphone preamplifier. With the
combination of unmatched sonic performance, powerful features, and solid reliability,
the m201 is a powerful recording tool designed to help you make the best recordings
of your career.

We have designed the m201 to be as easy and intuitive to use as possible. However,
we strongly recommend that you read this product manual thoroughly to familiarize
yourself with the unique features and capabilities of the m201.

Also, please do not hesitate to contact us directly if you have any questions, comments,
or concerns with your new m201 microphone preamplifier. Thanks for reading and
happy recording!!

-The Grace Design Team

Contents

Welcome 2

Important Safety Information 3

Front Panel Controls 4

Rear Panel Connections 5

Audio Connections 6

Power Connections 6

Preamplifier Operation 7

Ribbon Mic Mode 8

M-S recording with the m201 9

The Optional A/D Converter Features 9

Operating The A/D Converter Module 10

A/D Converter Sensitivity 11

Maintenance 14

Cleaning 15

Specifications 17

Signal Flow Diagram 18

Warranty Information 19

Manual Revisions 20

grace design m201

2

owner’s manual

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 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.

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

M+S WIDTH

100m

70m
30s

30m

70s

50m
50s

GRACE DESIGN USA

m201microphone preamplifier

HI-Z

1

48V

HI-Z

130V

ribbon

(

+10dB

)

20

30

40

50

60

INPUT MODE

+48V - 20dB

HI-Z

2

48V

HI-Z

130V

ribbon

(

+10dB

)

20

30

40

50

60

INPUT MODE

+48V - 20dB

Front Panel Controls

A

D

E

A

switch

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).

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.

D

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.

E

polarity reversal switch

The polarity reverse switch reverses the absolute phase

grace design m201

4

owner’s manual

C

B

GF

24 position gold contact gain

48V phantom power switch

H

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.

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.

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.

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.

I

120Vac

PUSH

PUSH

PUSH

1

3

2

4

PUSH

1

3

2

4

PUSH

PUSH

WORD/LOOP CLOCK

S/PDIF

LINE IN

TOSLINK

AES3 OUT

OUT

IN

RIGHT

LEFT

M+S O UT

130V

MIC IN

1

2

MIC IN

OUTOUT

MIC IN

OUTO UT

GRACE DESIGN USA

m 012

microphone preamplifier

1

2

Pb

LEAD FREE

RoHS

COMPLIENT

Rear Panel Connections

E

D

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

D

IEC AC power input

Accomodates the included 3 prong AC cable. Connect

to grounded outlet only.

ground.

C

B

A

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

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owner’s manual

Audio Connections

1

2

3

SHIELD

HOT

GND

(open)

Microphone 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. 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

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 pres­sure 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.

<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 preamplier input source from
the mic input connector to the front panel TRS jack. The input impedance of the in­strument 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 nega­tive, 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.

<figure 1> below.

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

6

owner’s manual

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

delay fuse with a 250V rating.

CAM SETTING LINE VOLTAGE FUSE VALUE

100V~ 100V~ 250V~ T 500mA L
120V~ 120V~ 250V~ T 500mA L

220V~ 220V~ 250V~ T 315mA L

240V~ 230V~ 250V~ T 315mA L
240V~ 240V~ 250V~T 315mA L

<figure 2 - fuse value table>

<figure 2> below. Be sure to use a time

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er 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 amplied 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
preamplier 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 xed input levels,

simply increase the gain until the optimum recording level is reached. If the peak in­dicator ashes red excessively with the gain control in the fully counterclockwise posi­tion, 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 ashing red, then

reduce the gain until the red stops flashing. Since red indicates a peak level which is

12dB before preamplier clipping (6dB in unbalanced mode), it is OK for it to come on
periodically during recording. If peak indicator ashes 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 pow­er 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 pow­er 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

8

owner’s manual

< >

14 16 18 20 0 0.1 0.2 0.3 0.4-0.3 -0.2 -0.1-0.4

LEVELHEADROOM (dB

)

1

2

-60 -50 -40 -32 -28 -24 -20 -18 -16 -14 -12 -10 -8 -6 -5 -4 -3 -2 -1 0

CAL

INT WORD LOOP

sLOCK

OFF

PRO

2WIRE

44

48 88 96 176 192

MSCH1-2

LINE

CONS

OVER

OVER

BA

FS SELECT CLOCK SOURCE ADC MODE

INPUT SENS

PEAK RESET

ADC SOURCE

/ MODE

(hold)

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 Tech­nique for Working in Stereo”. This paper (No. 1792) is available from the Audio Engi­neering Society web page (www.aes.org).

The Optional A/D Converter Features

A

J

I

H

G

B

F

C

D

E

grace design m201

9

owner’s manual

A

FS SELECT this switch is used to toggle through the available ADC sampling rates

B

CLOCK SOURCE this switch is used to select the ADC clock source

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

ADC SOURCE selects the input source which feeds the ADC module

I

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 fac­tory, or as an upgrade to your existing m201. If you need more information about up­grading 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

10

owner’s manual

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 il­luminated 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 in­dicators can programmed to remain lit indefinitely until the reset switch is pressed

(innite); 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 congured for one of

four standard A/D sensitivities. The following sections detail the operation and calibra­tion 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 recongure 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 congured 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

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 conduc­tive 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.

<figure 3>.

grace design m201

12

owner’s manual

84C

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TP2

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B VR4

VR2 A

VR1 B

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1 3

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1 3

3362

1 3

3362

1 3

FRONT PANEL

CH1 (A): VR2

10) Once all desired calibration adjustments have been made, press and hold the

11) Power down the unit, disconnect the AC power and reinstall the top cover.

CH1 (B): VR1

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.

CH2 (B): VR4

CH2 (A): VR3

<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 dened 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 xed. 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 gure 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

output termination information.

8) Apply power to the generator, preamplier, then the level meter.

9) Adjust the generator output level so that the preamplier output level is at the

desired red threshold. If the proper level can’t be reached, adjust the preamplier

gain control.

10) Locate VR2A (VR2B for channel 2) (
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 specic 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.

see <figure 3>) on the channel 1 audio circuit

<figure 1> for unbalanced

grace design m201

14

owner’s manual

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 instan­taneous 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 preamplier gain controls to maximum.

3) Turn on the m201 preamplier 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

next page)

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.

. Place the Volt meter probes into these holes.

(see figure 4

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 prod­uct to build up around the panel switches or knobs.

grace design m201

owner’s manual

15

C17

TP5

TP6

C51

C12

R40A

C36A

C53

R40B

C36B

J4B

P1

CHANNEL 1

P7

R17BR18B

CHANNEL 2

C13B

R62A

R14B

C52

R20B

R21B

D14A

R51A

R52A

R60A

R61A

R2B

R1B

C42A

C4B

R6B

C1B

C43A

R7B

D13A

C35A

R53A

D16A

D17A

R8B

C10B

J3B

U1B

R37B
D10B

R38B

C22B

R15B

C23B

R16B

RED WIRE

U5B

R25B

R26B

R27B

C27B

R28B

R29B

D14B

R51B

R52B

R60B

R61B

C42B

C35B
D13B

C43B

R53B

D16B

D17B

D8B

C24B

D7B

R71

C25B

R32B

R39B

R46B

R45B

R30B

D9B

R33B

U13

R34B

J7B

Q2B

Q3B

R31B

U6B

U7B

R62B

C44B

R63B

C45B

VR2B

U10B

R67B

R69B

R59B

C39B

R54B

R63A

C44A

C50

C45A

VR2A

U10A

R67A

R59A

R69A

J1B

C39A

R54A

R70

R3B

R4B

U12

-15

+15

RED W IRE

J3A

C14

R1A

R2A

C1A

R6A

C4A

R7AR8A

C10A

C13A

J4A

R37A

R38A

R14A

C22A

R15A

R16A

C23A

R17A

R25A

R26A

R27A

U1A

C27A

R18A

R28A

R29A

D10A

U5A

D8A

D7A

C24A

C25A

R32A

R19

R39A

R20A

R46A

U2

U4

+15

TP4

R21A

R31A

R30A

D9A

R33A

R34A

J7A

Q2A

Q3A

R45A

U6A

U7A

R9

R3A

R4A

C8

J1A

-15

TP3

U8A

P4

VR1A

K3A

C5A

OFFSET

C6A

TP1A

TP2A

R11A

U3A

D2A

C19A

C20A

R47A

R41A

R48A

C15A

D12A

R22A

R49A

P2

Q4A

D3A

D4A

K5A

C29A

C30A

R5AQ1A

K1A

D1A

K3B

D3B

C5B

C6B

R50A

R55A

C46A

TP1B

R56A

D15A

R6
4A

OFFSET

TP2B

VR1B

R11B

C19B

U3B

C20B

R41B

R47B

R48B

D2B

C15B

R22B

P5

D12B

R49B

U8B

R50B

R55B

C46B

Q4B

R56B

R64B

D15B

P8

K5B

C29B

C30B

C37B

C38B

R5B

C37A

Q1B

C38A

D1B

K1B

D4B

OFFSET TEST POINTS:
CH1> TP1A-TP2A
CH2> TP1B-TP2B

OFFSET TRIM POTS:
CH1> VR1A
CH2> VR1B

PEAK LED CAL POTS:
CH1> VR2A
CH2> VR2B

FRONT PANEL

<figure 4 - offset test point and peak LED adjust trim pots>

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owner’s manual

Specifications

preamplifier specifications (without A/D converter)

@ 40dB gain ± 0.2dB (50Ω source) 18Hz-65kHz
@ 40dB gain ± 3dB (50Ω source) 4.5Hz-350kHz

@ 20dB gain +25dBu out, 1kHz <.0008%
@ 40dB gain +25dBu out, 1kHz <.0009%
@ 60dB gain +25dBu out, 1kHz <.0070%

@ 40dB gain +25dBu out

SMPTE/DIN 1:1 (50Hz, 7kHz) <.0020%
SMPTE/DIN 4:1 (50Hz, 7kHz) <.0030%

@ 60dB gain 50Ω source -130dB
@ 60dB gain 150Ω source -127dB
@ 60dB gain 600Ω source -123dB

100Hz-20kHz @40dB gain <3°

Any Channel @ 40dB gain 1kHz -125dB
Any Channel @ 40dB gain 10kHz -115dB

@ 60dB gain, 3.5Vcm, 1kHz >70dB
@ 60dB gain, 3.5Vcm, 10kHz >70dB

1kHz, 100KΩ load +28dBu

Input 8100Ω
Input, ribbon mode 20kΩ
Output 190Ω

Green threshold -14dBu
Red threshold +16dBu

dimensions 2U, 19” rack mount x 10” deep
weight 16.5lbs (7.5kg)

100/120/230/240V~ 50-60Hz 20 Watts Max

Frequency Response

THD+N

Intermodulation Distortion

Noise - Referred to Input

Phase Deviation

Crosstalk

CMRR

Maximum Output Level

Impedance

Peak Led Meter

Weight and Dimensions

Power Consumption

A/D module specifications (line input)

20Hz-20kHz >115dB
“A” weighting >117dB

1kHz, -1dBFS, 20Hz-22kHz < 0.00026% (-112dB)

Frequency response

44.1kHz Fs 5Hz-21kHz 22kHz
48kHz Fs 5Hz-23kHz 24kHz

88.2kHz Fs 5Hz-41kHz 44kHz
96kHz Fs 5Hz-45kHz 48kHz

176.4kHz Fs 5Hz-54kHz 72.5kHz
192kHz Fs 5Hz-59kHz 79kHz
Full scale input level +16dB or +24dB (+/-2dB trim)

60Hz >65dB
1kHz >80dB
10kHz >60dB

IMD SMPTE 4:1 60Hz, 7kHz, -3dBFS <100dB (0.0008%)

Interchannel crosstalk <120dB

44.1-48kHz 13/Fs

+/-0.2dB -3dB

Sample rates, internal crystal (kHz)

Wide lock mode 40.1kHz-207kHz (+/-8% at each sample rate)
s-Lock™ mode +/-250ppm (+350, -400ppm typical)

Intrinsic Jitter, 200Hz-20kHz BW

Wide lock mode < 60ps RMS
s-Lock™ mode < 40ps RMS

Jitter Rejection Corner Frequency

Wide lock mode, -3dB, 12dB/octave 800Hz
s-Lock™ mode, -3dB, 12dB/octave 10Hz

Range A +22dBu = 0dBFS (18dB headroom*)
Range B +18dBu = 0dBFS (14dB headroom*)

*can be calibrated for any setting between +18dBu = 0dBFS and +24dBu = 0dBFS

Dynamic range

THD+N

CMRR

Group delay

44.1, 48, 88.2, 96, 176.4, 192

External Clock Lock Range

A/D sensitivity

grace design m201

owner’s manual

17

AES3 1

INPUTS

OPTIONAL ANALOG TO DIGITAL CONVERTER MODULE

2-CH SPDIF

CH 1 OUT A

6-CHANNEL

ANALOG OUTPUTS

CH1 MIC

TOSLINK

LOOP SYNC IN

WORD CLOCK

CLOCK OUT

s-Lock PLL

6-CHANNEL

MICROPHONE AMPLIFIER

HI-Z INPUT AMP

OUTPUT DRIVERS

BALANCED

WIDE RANGE PLL

CH1 HI-Z

AES3 TX

AES3 TX

ADC

CH1 DPA

DPA INPUTS (OPTIONAL)

-20dB

-20dB

CH 1 OUT B

AMPLIFIER

M-S SUMMING

AMPLIFIER

M-S DIFFERENCE

LEFT OUT

RIGHT OUT

AES3 2

INTERNAL CLOCK

LINE IN LEFT

LINE IN RIGHT

FROM M-S OUTPUT

FROM PREAMP CH 1-2

ADC INPUT SELECTOR

CLOCK OUT SELECT

M-S OUTPUTS

CLOCK CONTROL

FS SELECT

+48V

+130V

MID

INPUTS

CH 2 OUT A

ANALOG OUTPUTS

CH2 MIC

MICROPHONE AMPLIFIER

OUTPUT DRIVERS

BALANCED

2-CHANNEL

CH2 HI-Z

CH2 DPA

DPA INPUTS (OPTIONAL)

CH 2 OUT B

SIDE

CLK SELECT

ADC INPUTS

DIGITAL OUTPUTS

RIBBON +10dB

+48 OFF

M-S WIDTH

HI-Z INPUT AMP

-20dB

-20dB

+48V

+130V

RIBBON +10dB

+48 OFF

GRACE DESIGN

m201 SIGNAL FLOW DIAGRAM

Signal Flow Diagram

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owner’s manual

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 [phone] Monday­Friday 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

A Initial release 04/25/2007 mbg

B 3 Changed voltage range and power specifications 04/26/2007 mbg

B 4 Power switch description changed to standby switch. 04/26/2007 mbg

B 6 Added power mains disconnect information 04/26/2007 mbg

B 13 Added signal flow diagram 04/26/2007 edg

C 9-12 Added A/D module infirmation 11/08/07 edg

D 7 changed fuse values for 220V-250V from 250 to 315mA 4/24/08 edg

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owner’s manual