222 HARTREY AVE., EVANSTON, IL, 60204 U.S.A.
AREA CODE 312/866-2200 • CABLE: SHUREMlCRO
TWX: 910-231-0048
TELEX: 72-4349
MICROPHONES AND ELECTRONIC COMPONENTS
DATA SHEET
MODELS M64 AND M64-2E
STEREO PREAMPLIFIERS
GENERAL
The Shure Models M64 and M64-2E Stereo Preamplifiers are designed to furnish the voltage gain
and equalization necessary to operate magnetic
phono cartridges (such as the Shure DYNETIC
®
Cartridges), and tape playback heads with audio
amplifiers that have no equalization. In addition, the
units may be used without equalization for microphones or as buffer amplifiers.
Typical Applications:
l Conversion of stereo record playing systems
from ceramic to magnetic cartridges.
l Preamplifier for microphones.
l Low gain buffer amplifier where long cable
lengths are extended to a preamplifier input.
Advantages include complete freedom from microphonics, extremely low noise, the ability to use
15m (50 ft) or more of output cable, and years of
maintenance-free performance. The operating temperature range is from 7°C (20°F) to 57°C (135°F).
The Model M64 operates on 108-132 volts, 50/60
Hz power line, or from an auxiliary 24 to 36 volt dc
supply such as the Shure Model A67B Battery Power
Supply. The M64-2E is identical to the M64 except
that it operates on a line voltage of 216-264 volts,
50/60 Hz.
The Model M64 and M64-2E feature a single 3-
position slide switch for selecting equalization for
Phono, Tape, or Flat. The Phono position provides
the Standard RIAA Equalization for phono records.
The Tape position provides the Standard 7½ IPS
NAB Equalization for tape, and the Flat position
provides a flat amplifier for microphones or as a
buffer amplifier for magnetic phono cartridges when
long lines or switching systems are necessary
between the turntable and main equalized preamplifier. (NOTE: When used as a buffer amplifier,
the Low Level Outputs should be used). The input
and output jacks will accept standard phono plugs.
There are input jacks for Channel 1 and Channel 2;
output jacks for Ch. 1 High Level, Ch. 1 Low Level,
Ch. 2 High Level, and Ch. 2 Low Level.
SPECIFICATIONS
Gain
Gain measured at 1 kHz with input through 680
ohms and output terminated in 47 kilohms.
Equalization
Switch Position output
Flat
Phono
Tape
Frequency Response
Flat:
Phono:
± 2 dB from 20 Hz to 20 kHz
± 2 dB of the Standard RIAA curve from
40 Hz to 15 kHz
Tape:
± 2 dB of the 7½ IPS NAB curve from
50 Hz to 15 kHz
TYPICAL FREQUENCY RESPONSE
Distortion
Under 1% total harmonic distortion for an output
of 2 volts at 1 kHz in Phono, Tape or Flat positions.
In the Phono position the total harmonic distortion
is less than 1% at 30 Hz with 2 volts output.
Clipping Level
The minimum input clipping levels at 1 kHz are:
Flat: 250 mV
Phono: 100 mV
Tape: 80 mV
Channel Separation
50 dB or better at 1 kHz
Channel Balance
Channels matched within 2 dB at 1 kHz
High Level
+27.5 dB
+34.5 dB
Low
output
+ 4.0 dB
+11.0 dB
+37.0 dB +13.5 dB
FIGURE 1
Level
Copyright 1984, Shure Brothers Inc.
27A2076 (DB)
Printed in U.S.A.
Hum and Noise
Phono:
Flat:
Better than 71 dB below 10 millivolt
input from 20 Hz to 20 kHz
Better than 64 dB below 10 millivolt
input from 20 Hz to 20 kHz
Operating Voltage
M64:
M64-2E:
120 volts ± 10%, 50/60 Hz or 30 volts
± 20% dc. Listed by Underwriters’
Laboratories, Inc. (Applies to Model
M64).
240 volts ± 10%, 50/60 Hz or 30 volts
± 20% dc
Battery Operation
The M64 and M64-2E may be powered by three
Eveready 216 Batteries in series or equivalent
power source connected to 30 V.D.C. jacks. Battery
life is over 100 hours. The Shure Model A67B
power supply, or power jacks on Shure’s Models
M63, M67, or M68, may be connected to the 30
V.D.C. jacks to power the M64 or M64-2E. These
jacks, which provide 29 Vdc (26 Vdc at 5 mA max.),
can also be used to power external equipment.
Input Impedance
Resistance is 50,000 ohms at 1 kHz
Capacitance is 350 pF
Output Impedance
High Level: Less than 1000 ohms at 1 kHz (mini-
mum recommended load is 22,000
ohms)
Low Level:
600 ohms (any load on Low Level
output will not affect input clipping
level)
Dimensions
See Figure 2
Weight
794 grams (1¾ lb)
Power Consumption
5 watts
Temperature Range
Operating:
Storage:
-7°C to 57°C (20°F to 135°F)
-29°C to 71°C (-20°F to 160°F)
INSTALLATION
should be located away from motors or other hum
producing power sources and away from intense
heat sources. Should hum be a problem in a given
system or installation, one or more of the power
plugs may be reversed to reduce hum. If the turntable has a grounding wire, this wire may be connected to the “ground” screw on the Preamplifier
to reduce hum pickup.
WARNING
The use of the M64 and M64-2E Stereo
Preamplifier with power amplifiers of the
transformerless (ac-dc) type may result in a
shock hazard. A suitable power line isolation transformer should be used with such
equipment.
OPERATION
Connections:
a. Set selector switch to the desired function.
This automatically selects the proper equalization (frequency response) for both channels.
b. For the equalized Phono (RIAA) or Tape (NAB)
position, connect the signal leads from the
phono cartridge or tape head to the jacks
marked “Channel 1 Input” and “Channel 2
Input.” * For the Flat position using two
separate high-impedance microphones, connect the cable from one high-impedance microphone to jack marked “Channel 1 Input.”
The cable from the other high-impedance
microphone should be connected to the jack
marked “Channel 2 Input.” For single highimpedance microphone applications connect
to either Channel 1 or Channel 2. NOTE:
If low-impedance microphones are to be used,
a suitable input transformer such as the Shure
Model A95 Series should be used. Attention
must be given to information contained in the
data sheets of the phono cartridges, tape
heads, or microphones regarding their connections, phasing and grounding.
c. Connect Ch. 1 and Ch. 2 (High Level or Low
Level) output jacks to the corresponding input
jacks of the power amplifier, preamplifier,
tape recorder or mixer.† If it is found neces-
sary to ground the M64 or M64-2E Preamplifier
chassis, ground connection may be made
To reduce the risk of fire or electric shock
do not expose this appliance to rain or
The M64 and M64-2E Preamplifier may be mounted to an amplifier chassis or cabinet by means of
screws passed through mounting slots at base of
M64 and M64-2E Preamplifier chassis. The Preamplifiers can be mounted in any position for normal
operation, but for best results, the Preamplifiers
* The Flat position may be used for high-impedance
microphones, or for phono cartridge or tape head
buffering applications in which the output of the
M64 or M64-2E is connected to an equalized amplifier input.
† The High Level outputs may be connected to
high-level auxiliary inputs, and the Low Level
outputs may be connected to low-level microphone inputs (or equalized phono or tape head
inputs in buffering applications).
OVERALL DIMENSIONS
FIGURE 2
to the “Ground” screw on the Preamplifier
chassis.
d. If ac power operated, insert the M64 or M64-2E
power line cord into a proper power outlet,
preferably one controlled by the power amplifier’s On-Off switch. Be sure power switch
on M64 or M64-2E is in the “On” position
when remotely turned “On” & “Off”.
WARNING
Voltages in this equipment are hazardous
to life. Refer servicing to qualified service
personnel.
Balanced Line Output:
For professional low-impedance balanced line
use, such as broadcast systems or recording consoles, an external line matching transformer (Shure
Model A95 Series) may be added to each High
Level output of the M64 or M64-2E. The resultant
output level will be approximately -32 dBm. If a
higher output level is necessary (-20 dBm) the
following change can be made by qualified service
personnel only, which will increase the output level
by approximately 12 dB.
1. Unplug the ac line cord before removing
cover.
2. Remove the three large Phillips head screws
that hold the case cover in place.
3. Lift off cover.
4.
Remove printed circuit board assembly from
nylon fasteners by squeezing upper protruding tab on circuit board side inward and sliding
board outward and off the fastener.
5. Lift the printed circuit board assembly straight
up until 1 k resistors R13 and R14 are ac-
cessible. (See bottom illustration on page 4)
Note R13 and R14 are raised on longer leads
than the other resistors for ease of identification.
6. Solder 330 ohm ¼ watt resistors across (in
parallel with) the extended lead wires of R13
and R14 (330 ohm resistor across the 1000
ohm resistor). The extra lead length of R13
and R14 makes this very easy and it is not
necessary to alter the printed circuit board or
its components.
7.
Remount the printed circuit board assembly
and replace the cover, being careful not to
pinch any wires when closing up the unit.
NOTE: This change will decrease the input
clipping level of the preamplifier to about 25
mV so that if high-output cartridges or very
highly modulated records are used the pre-
amplifier may tend to clip on loud passages.
If the gain increase desired is less than 12 dB,
the following resistors can be used in parallel
with R13 and R14 instead of the 330 ohm
resistors.
for 3 dB, use 2.2 kilohms
for 6 dB, use 1 kilohm
for 9 dB, use 560 ohms
FULL ONE-YEAR WARRANTY
Shure Brothers Incorporated (“Shure”), 222
Hartrey Avenue, Evanston, Illinois 60204, warrants
to the owner of this product that it will be free, in
normal use, of any defects in workmanship and
materials for a period of one year from date of purchase. You should retain proof of date of purchase.
Shure is not liable for any consequential damages.
If this Shure product has any defects as described
above, carefully repack the unit, have it insured, and
return it prepaid to:
Shure Brothers Incorporated
Attention: Service Department
222 Hartrey Avenue
Evanston, Illinois 60204
If you are not in the United States, return the unit
to your dealer or Authorized Service Center for
repair. The unit will be repaired or replaced and
returned to you promptly, and if it cannot be repaired or replaced, you may elect to receive a
refund.
MODEL M64-2E CIRCUIT
PRINTED CIRCUIT BOARD
MODEL M64 CIRCUIT
NOTES:
1. ALL CAPACITORS IN MFD AND 100 VOLTS OR MORE UNLESS
OTHERWISE SHOWN.
MFD x VOLTS.
2. ALL RESISTORS 10%, 1/4 WATT UNLESS OTHERWISE SHOWN.
3. THE FOLLOWING SYMBOL WITH LETTER DESIGNATION DENOTES
A TERMINAL ON PRINTED CIRCUIT BOARD ASSEMBLY.-
4.
DENOTES A.C. VOLTAGES
DENOTES D.C. VOLTAGES
ALL VOLTAGES MEASURED WITH A.C. LINE = 120V., 60HZ, PHONO
EQUALIZATION, INPUT TO CHANNEL 1 = 10 MV RMS AT 1000 HZ.
D.C. VOLTAGES MEASURED WITH 11 MEGOHM VTVM.
VOLTAGES MEASURED WITH I MEGOHM VTVM.
ARE TYPICAL AND MAY VARY ±20%. CHANNEL I VOLTAGES
ONLY SHOWN. CHANNEL 2 IS SIMILAR.
ELECTROLYTIC CAPACITORS SHOWN IN
VOLTAGES
A.C.
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