Owner`s manual Rev B
m801
microphone preamplifier
Manual RevB
owner’s manual
all contents ©2006 Grace Design/ Lunatec LLC
Welcome
Thank you for purchasing the Grace Design m801 microphone preamplifier. With the
combination of unmatched sonic performance and total reliability, the m801 is the ultimate, state of the art microphone preamplifier solution.
We have designed the m801 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 m801.
Also, please do not hesitate to contact us directly if you have any questions, comments,
or concerns with your new m801 microphone preamplifier. Thanks for reading and
happy recording!!
-The Grace Design Team
Contents
2
Welcome
2
Important Safety Information
3
Front Panel Controls
4
Rearpanel Connections
5
Power Supply
5
Installation
6
Preamplifier Operation
7
Maintenance
8
Specifications
11
Cleaning and Maintenance
12
Warranty Information
12
grace design m801
owner’s manual
Important Safety Information
GENERAL
•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: 100-120/220-240V~ 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: preamplifier - 6.8kg (15lbs) / power supply unit - 2.8kg (6.25lbs)
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.
DC POWER OUTPUT
This symbol, located on the equipment and in this manual, indicates a DC
power output connection.
SERVICE INFORMATION
The Grace Design m801 contains no user serviceable components. Contact Grace Design for repair and upgrade information. In the event that your Grace Design m801
needs to be returned to the factory, contact us for a return authorization number.
grace design m801
owner’s manual
3
Front Panel Controls
A
1
B
2
40
30
50
20
+48V
60
- 20dB ribbon
3
40
30
50
20
+48V
4
40
30
60
50
20
- 20dB ribbon
60
30
50
20
- 20dB ribbon
+48V
5
40
+48V
60
- 20dB ribbon
GRACE DESIGN USA
C
A
24 position gold contact gain switch
Each gain control has 24 positions and adjusts the
voltage gain from 18dB to 64dB in 2dB steps. For
reference, the 9 o’clock position is 28dB, the 12
o’clock position is 40dB, and the 3 o’clock position
is 52dB.
B
bi-color LED peak indicator
The LED peak indicator, which monitors the output
signal, 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 page 8).
C
48V phantom power switch
The phantom power switch (labeled +48V) connects the +48V power supply to pins 2 and 3 on
the XLR input connector. This switch illuminates
red. It should be noted that the LED in this switch
actually monitors the voltage at the input. With no
microphone 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 application.)
4
grace design m801
owner’s manual
D
D
E
F
phase reversal switch
The phase reverse switch reverses the absolute
polarity 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.
E
-20 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.
F
ribbon mic mode switch
This switch activates a 10dB increase in overall
preamplifier gain while simultaneously disabling
the 48V phantom power circuit to protect ribbon
microphones. As well, the input coupling capacitors are bypassed.
4
30
20
+48V
-
Rearpanel Connections
A
8
A
XLR mic input connector
B
7 pin XLR DC input
6
OUT B
5
C
XLR output connector
Output connections are made via male XLR connectors with pin 2 positive, pin 3 negative and pin
1 ground.
parallel XLR output connector
An additional set of parallel XLR outputs are provided for sending line signals to additional recording devices or mixers.
m801 power supply
front
GRACE DESIGN
+24
-24
+5
+48
BOULDER, CO USA
O
I
CAUTION: ALWAYS CONNECT DC POWER CORD
BEFORE TURNING ON MAIN POWER
A
B
A
LED Voltage indicators
B
Power switch
C
AC line input
D
DC output
E
Ground - ISO switch
rear
FOR m801
ONLY
PUSH
120Vac
6
2
4
C
1
7
5
D
3
E
grace design m801
owner’s manual
5
PUSH
1
3
2
5
D
D
An 8’ (2.8m) DC power cord is supplied to connect
the power supply unit to the preamplifier unit.
This cord can be identified by the 7 pin XLR connectors at each end.
OUT A
OUT B
7
C
5
6
OUT B
8
PUSH
1
OUT B
MIC IN
OUT A
7
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.
3
2
OUT A
8
B
MIC IN
6
7
OUT A
DC
INPUT
PUSH
1
3
MIC IN
2
2
PUSH
MIC IN
3
PUSH
m801
microphone
preamplifier
1
GRACE DESIGN USA
Installation
AUDIO CONNECTIONS
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 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 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.
HOT
2
GND
1
SHIELD
3 (open)
figure 1 - Unbalanced output cable termination
POWER CONNECTIONS
An 8’ (2.8m) DC power cord is supplied to connect the power supply unit to the preamplifier unit. This cord can be identified by the 7 pin XLR connectors at each end.
Please note that the DC power cord should be connected before the AC power is
turned on. This prevents incorrect power sequencing which can cause damage to the
audio circuits. To avoid any interference with the low level audio circuitry, the power
supply should be located at least 3’ (1m) from the preamplifier unit.
WARNING: A damaged DC power cord can create a shock hazard as
voltages of 72VDC can be present. Do not operate the m801 with
a damaged DC power cord. Replace a damaeged DC power cord
with a replacement from Grace Design.
A standard AC power cable is included. For safety, the power supply cord must be
connected to a grounded outlet.
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 power supply unit, open the trap door next to the IEC power inlet with a small
screwdriver. Carefully pull the voltage select cam straight out and then insert with the
desired voltage showing. Do not try to rotate the cam while it is in the power input
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grace design m801
owner’s manual
module. Replace the fuses with the proper value selected from table 1 below. Be sure
to use a time delay fuse with a 250V rating.
CAM SETTING
LINE VOLTAGE
FUSE VALUE
100V~
100V~
250V~ T 750mA L
120V~
120V~
250V~ T 750mA L
220V~
220V~
250V~ T 500mA L
240V~
230V~
250V~ T 500mA L
240V~
240V~
250V~T 500mA L
table 1 - fuse value table
CHECK LINE VOLTAGE SETTINGS
The power supply unit 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.
TURNING THE POWER ON
The power switch is located on the front panel of the Power Supply Unit. Switching
the rocker switch to the I position turns the mains power on. Switching the rocker
switch to the O position turns the mains power off.
GROUNDING OPTIONS
In certain installations, it may be desirable to separate the preamplifier signal ground
from the chassis and earth grounds. Noise inducing ground loops can be broken while
retaining the safety feature of the grounded AC power cord. The m801 should not be
operated with a ground lift or “cheater” plug on the AC power cord. To separate the
preamplifier signal ground from the chassis and earth grounds, simply set the AUDIO
GND toggle switch on the rear panel of the power supply unit to the desired setting
(ISO or EARTH).
MOUNTING
The m801 power supply can be rack mounted in a standard 1U rack tray, and two
power supply units will fit side by side. The power supply unit chassis has a #10-32
threaded insert on the bottom for mounting. Use a #10-32 x 1/2” or a #10-32 x 3/8”
machine screw, no longer than 1/2”.
Preamplifier Operation
SETTING THE GAIN
First, turn the gain control fully counter-clockwise and check that the +48V phantom
grace design m801
owner’s manual
7
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 indicator flashes 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 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 adjust the recorder input control for the optimum recording level.
RIBBON MIC MODE
Pressing the ribbon switch optimizes the m801 channel for ribbon microphones by
boosting the gain by 10dB while disabling 48V phantom power. Before activating ribbon mic mode, make sure the channel’s gain is fully down (counter-clockwise) and 48V
phantom power is off. Now simply press the ribbon switch 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, nothing will
happen. However, if the 48V phamtom switch remains depressed and the ribbon mic
switch becomes inadvertantly disengaged, 48V phantom will consequently 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 switch is
turned on the preamplifier will wait until the phantom power voltage 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 m801’s signal path. Incidentally, the ribbon mode works very
well with many lower output dynamic microphones as well as ribbon types.
Maintenance
The model m801 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 the Grace Design factory.
PEAK LED ADJUSTMENT PROCEDURE
The peak LED threshold levels may be adjusted to a user defined operating level. This
8
grace design m801
owner’s manual
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 VTVM with dBu or dBm scale
•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 m801
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) Set the input attenuator to +20dBu range. If the level meter has an unbalanced input, refer to figure 1 (p. 6) for unbalanced output termination information.
HOT
SHIELD
2
1
3
XLR MALE
figure 2 - Unbalanced input cable
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 VR1 (see figure 3 p.10) 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 channels 2 through 8.
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/recorder.
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.
INPUT OFFSET ADJUSTMENT
The input amplifiers in the m801 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
grace design m801
owner’s manual
9
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 preamplifier gain controls to maximum.
3) Turn on the m801 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 TP1 and TP2 (figure 3). Place the Volt meter probes into these holes.
5) Locate DC offset potentiometer VR2 and rotate it for a reading 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.
VR2 (OFFSET ADJUST)
TP1 AND TP2
(OFFSET TEST POINTS)
+48 -18 +18 +15 -15 +5
C8
D8
J3
C11
D3
Q2
R23 R25
R22 C25
C27 R26
R24
U8
R30 R34
R31
D10
D9 Q3
R29
C30 R33
R32
U5
C4
C3
R12
R11
D1
C24
C29
C23
C28
grace design m801
owner’s manual
C46 R40
R36 R39
C33
C32
U9
figure 3 - offset test point and peak LED adjust trimpots
10
J7
C39
R41
C31
D13
C34
R35 R38
C45 R37
K3
C44
U10
C40
R4
R2
C17 C16
C10 R20
D7
C9
D6
R19
R18
D5
R17
D4
R15
C5
U4
Q1
U7
C41
J5
C6
R16
R14
R13
C2
C1
R3
R1
D2
J2
U1
R45
R44
C35
L1
RED WIRE
D12
C12
D11
C13
K4
C36
R27
R21
C21
C19 C18 R52
R5
K2
K1
C26
C14
U2
R42
U6
R7
R6
J8
C37
C15
C7
C42
R47
R46
R28
R43
R8
C38
TP2
D14
U3
AT132 REV
TP1
L2
R9
OFFSET
J4
C22
C20
R10
J1
VR1(PEAK LED ADJUST)
R51
R50
R49
R48
C43
J6
Specifications
PREAMPLIFIER SPECIFICATIONS
FREQUENCY RESPONSE
@ 40dB gain ± 3dB 50Ω source
4.5Hz-350KHz
@ 40dB gain ± 0.2dB 50Ω source
18Hz-65KHz
THD+N
@ 20dB gain +20dBu out, 1kHz
<.0008%
@ 40dB gain +20dBu out, 1kHz
<.0009%
@ 60dB gain +20dBu out, 1kHz
<.0070%
INTERMODULATION DISTORTION
@40dB gain +20dBu out
SMPTE/DIN 1:1 (50Hz, 7kHz)
<.0020%
SMPTE/DIN 4:1 (50Hz, 7kHz)
<.0030%
NOISE - REFERRED TO INPUT
@60dB gain 50Ω source
-130dB
@60dB gain 150Ω source
-127dB
@60dB gain 600Ω source
-123dB
PHASE DEVIATION
100-20KHz @40dB gain
<3°
CROSSTALK
Any Channel @40dB gain 1kHz
-140dB
Any Channel @40dB gain 10kHz
-130dB
CMRR
@60dB gain, 3.5Vcm, 1KHz
>70dB
@60dB gain, 3.5Vcm, 10KHz
>70dB
PHANTOM POWER
Voltage +48V
+0.9/ -0.0
6.8kΩresistor match tolerance
+/- 0.1%
MAXIMUM OUTPUT LEVEL
1kHz, 100KΩ load
+28dBu
IMPEDANCE
Input
4350Ω
Output
190Ω
DIMENSIONS
15lbs (6.8kg)
Weight
Height
2U
Width
19”
10”
Depth
POWER SUPPLY SPECIFICATIONS
POWER CONSUMPTION
100-240VAC 50/60Hz
60 Watts max
DIMENSIONS
Weight
6.25lbs (2.8kg)
Height
1.7”
Width
8.5”
Depth
8.5”
grace design m801
owner’s manual
11
Cleaning and Maintenance
Your m801 amplifier 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 cleaning 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.
Warranty Information
Grace Design warrants all of our products to be free of defective parts and
workmanship 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 (303-4437454 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.
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grace design m801
owner’s manual
Manual Revisions
Revision
Page
Change
Date
Initials
A
all
initial release
5/23/07
edg
B
all / 13
updated layout / added revision table
1/29/09
edg
grace design m801
owner’s manual
13
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