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OPERATION lnput lmpedance (at 1 kHz)
Resistance: 50
kilohms
Capacitance: 160 picofarads
Output Impedance (at 1 kHz)
High Level: Less than 2000 ohms (minimum recom-
mended load is 22,000 ohms)
Low Level: 600 ohms (any load on Low Level output
will not affect input clipping level)
Power Consumption
5 watts
Operating Voltage 120 or 240 volts ac
+ 1O0/0, 50160 Hz (internally selec-
table)
Temperature Range Operating:
-7" to 57" C (20" to 135" F)
Storage: -29" to 71 " C (-20" to 160" F)
Dimensions
See Figure 2
Net Weight 986 grams (1
Ib 2-112 oz)
144mm 104mm r(5-9/16 IN. ) 1 (4-3/32 IN.I~
OVERALL DIMENSIONS
FIGURE
2
INSTALLATION
To reduce the risk of fire or electric shock, do
not expose this appliance to rain or extreme
moisture.
The
M64A can be operated on any flat surface, or
(with adequate space) be mounted to an amplifier
chassis or cabinet using screws through the
M64A's
mounting flanges. The unit can be mounted in any posi-
tion for normal operation, but for best results, it should
be located away from motors, lighting dimmers, or other
hum-producing power sources and away from intense
heat sources.
Should hum be encountered in a sound system or
installation, one or more of the equipment power plugs
may be reversed to reduce hum. If the turntable has a
grounding lead, this wire can be connected to the
M64A
Ground screw to reduce hum pickup.
WARNING
Use of the M64A 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 equip-
ment.
1. Set the selector switch to the desired function
(Phono, Flat or Tape). This automatically selects the
proper equalization (frequency response) for both
channels.
2. For the equalized Phono
(RIAA) or Tape (NARTB) posi-
tions, connect the signal leads from the phono car-
tridge or tape head to the
M64A jacks marked Chan-
nel
1 lnput and Channel 2 Input. Note that the Flat
position can be used for phono cartridge or tape
head buffering applications in which the
M64A out-
put is connected to an equalized amplifier input.
3. For the Flat position using two high-impedance
microphones, connect each microphone cable to
one of the
M64A lnput connectors. If a single high-
impedance microphone is used, connect it to either
lnput connector. NOTE: If low-impedance
microphones are to be used, a suitable line match-
ing transformer such as Shure's A95 Series should be
used.
4. Refer to the phono cartridge, tape head or
microphone data sheet
for details on connections,
phasing and grounding.
5. Connect the Channel 1 and Channel 2 Output jacks
(High or Low Level) to the corresponding input jacks
of the power amplifier, preamplifier, tape recorder or
mixer. The High Level outputs can be connected to
high-level auxiliary inputs, and the Low Level out-
puts can be connected to low-level microphone in-
puts (or equalized phono or tape head inputs in buf-
fering applications).
6. If grounding is necessary, the associated equipment
ground lead can be attached to the
M64A Ground
screw.
7. Insert the M64A power line cord into a proper power
outlet (120
Vac +lo%, 50160 Hz), preferably one
controlled by the power amplifier's on-off switch.
Make certain the
M64A Power switch is turned on if
the unit is to be remotely turned on and off.
SERVICE
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 such as Shure's A95
Series can be added to each
M64A High Level output.
The resultant output level is approximately -32
dBm. If
2
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a higher output is required (-20 dBm), the following
modification can be made to increase the output level
by approximately
12 dB.
1. Unplug
the
ac power line cord.
2. Remove the two screws securing the top cover and
remove the top cover.
3. Locate the vertically
mounted main printed circuit
attached to the front panel. Resistors R13 and R14
(1 k, 114W, 10%) are soldered to the foil side of the
board.
4. Carefully wrap and solder the leads of 330-ohm,
114W resistors across (in parallel with) the leads of
R13 and R14. Use a low-wattage soldering iron and
avoid contact with the circuit board or other com-
ponents.
5. Replace and secure the top cover.
240 Vac Operation
The M64A as supplied will operate from a 120 Vac
10%, 50160 Hz power source. For operation from a 240
Vac k lo%, 50160 Hz power source, perform the follow-
ing steps.
1. Unplug the ac line cord and remove the two black
self-tapping screws securing the top cover.
2. Remove the top cover.
3. Locate the voltage selector switch and move it to
the 240 position.
4. Replace the ac line cord and plug (if necessary) with
one designed for the 240
Vac source. If the M64A
is to be used outside the U.S. and Canada, local
regulations may require replacing the line cord with
one having wire insulation colors as follows:
"Live" or
"Hot" Neutral Earth or Ground
NOTE: The above modification decreases the input
clipping level to approximately 25
mV. This means that U.S.,
Canada Black
White Green
Europe Brown Blue GreenlYellow if high-Out~ut cartridges Or very modulated 5. Replace the top cover and mark the rear panel to records are used, the M64A may tend to clip on loud
reflect the new operating voltage.
Dassaaes. If a gain increase of less than 12 dB is
desire& use the following resistor values instead of 330
ohms.
Gain Resistor
3 dB 2.2k
6 dB lk
9 dB 560 ohms
PRINTED CIRCUIT BOARDS
COMPONENT SIDE
M-64 TOP SILK
