Shure m 61 owners manual

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E = Ill = a MICROPHONES IIIIII ELEETIIOIIIG COMPONENTS

DATA SHEET

M61 SERIES

TRANSISTOR STEREO PREAMPLIFIERS

General: The Shure M61 Series Transistor Preampli-
tiers are designed to furnish the voltage gain and equal-
ization necessary to operate magnetic phono cartridges
(such as the Shure Dynetic Cartridges) and tape playback
heads with standard audio amplifiers. One of the primary
uses of the M61 is in conversion of Stereo systems from
ceramic cartridges to magnetic cartridges. It can also be
used without circuit modification as a preamplifier for
microphones. Advantages include complete freedom from
microphonics, extremely low noise, the use of 50 feet or
more of output cable in phono" and tape" positions,
and years of maintenance-tree performance. The operat-
ing temperature range is from 32°F. (0°C.) to 140°F.
(60°C.).

The Model M61-1 operates on 105-125 volts 50-60
Hertz power line.

The Model M61-2 operates on 210-240 volts 50-60
Hertz power line.

The Model M61-3 operates on battery power.

The Model M61 Preamplifiers feature a single slide
switch for selection of either phono (FIIAA), tape (NAB),
or a microphone (MIC) function. The FIIAA position pro-
vides the Standard Equalization for phono records. The
NAB position provides the Standard Equalization for
tape and the MIC position provides a flat amplifier for
microphones.

The preamplifier has dual input and output iacks which
will accept standard phono pugs.

The input impedance is optimized for Dynetic and
magnetic phono cartridges, for tape heads, and for low
or medium impedance microphones.

The output load will typically be the 500,000 ohm
Tuner or Ceramic input of an Amplifier. Earphones of
4,000 ohms or more nominal impedance can be con-
nected directly, or through a 1,000,000 ohm control, to
the M61 output with the following specifications obtain-
ing down to 250 Hertz or lower.

SPECIFICATIONS

Gain: RIAA (Phone) 46 db (5 millivolts input produces 1.0 volt)
NAB (Tape) 41 db (2 millivolts input produces 0.225 volt)
MIC 63 db (2 millivolts input produces 2.8 volts)

Frequency Response and equalization:
Phono: Standard FllAA equalization
Tape: Standard NAB equalization
MIC: Response 12 db from 20 Hz. to 15,000 Hz.

Input Impedance:

Phono end tape: Approximately 50,000 ohms at 1,000 Hz.
Microphone: Approximately 20,000 ohms at 1,000 Hz.

Output Impedance:
Low output impedance (less than 1,000 ohms at 10,000 Hz. for
phono end tape functions)

Channel Separation:
50 db or better (at 1,000 Hz.)

Copyright, 1962, Shure Brothers, Inc.
27A206 (4'68)

Channel Balance:
2 db at 1,000 Hz. (for Phone end Tape functions)

Hum and noise:
76 db below to millivolt input, unweighted

Distortion:
Less than 1%. Measured at I volt output

Output Clipping level:
More than 4.5 volts (at 1,000 Hz.)

Available power supplies:

1. 105-125 volts 50-60 Hertz (included in Model M61-1)

2. 210-240 volts 50-60 Hertz (included in Model M61-2. Avail-
able separately as Model P5220).

3. Battery [included in Model M61-3. Available Separately as
Model P5530).

The battery (Burgess type K20 or Eveready type 430) provides

170 hours minimum of operation.

Overall Dimensions: Preamplifier or power supply
Length 5% inches (133.4 mm)
Width 2-7/16 inches (61.9 mm) preamplifier has plug pins ex-
tending en additional /2 inch (12.7 mm)
Height 2-5/16 inches (58.7 mm) over switch button

Weight: Net weight (M61-1) 1% pounds (567g)
Packaged weight (M61-1) 2/: pounds (1133.8g)

installation: The M61 Preamplifiers and power sup-
ply may be mounted on an amplifier chassis or cabinet
by using the wood screws or machine screws provided.
The Preamplifier can be mounted in any position for
normal operation; but for best results, the Preamplifier
should be located away from motors or other hum pro-
ducing 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 re-
versed to reduce hum.

Printed in U.S.A.

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Caution: The use of the M61 Stereo Preamplifier Wm necessary 0 "9'0""d" 19 M51 Preamplifier
with other power amplifiers of the transformerless (AC- chassis, a wire can be connected ° one Of "9 screws
DC) type may be a shock hazard. holding the bottom plate to the chassis.

A suitable power line isolation transformer should d. If AC power operated, insert the M61 power
be used. line cord in a proper power outlet preferably one con-
trolled by the power amplifiers On-Off switch. Be sure
power switch on preamplifier is in the ON position. If
the battery power supply is used, an 0N~OFF switch is
provided.

Connections: a. Set selector switch to the desired
function. This automatically selects the proper equaliza-
tion or frequency response for both channels.

b. For the Phono (FIIAA) position, connect the signal

leads from the phono cartridge to the jacks marked IN GREEN ORANGE GREEN ORANGE GREEN ORANGE
at channel A" and channel B. For the microphone WK ELL (
position using two separate microphones, connect the

cable from one microphone to jack marked IN" at

channel A. The cable from the other microphone T 1) ?
should connect to the jack marked IN at channel B.
For single microphone application connect to either ttnlEAWIngswlJN Mitslwnnglllqu NAngJ-IPgHsmoN

channel A" or B".

Attention must be given to information contained in
the data sheets of the phono cartridge, tape head, or
microphone regarding their connections, phasing, and

Guarantee: This Shure High Fidelity Component is
guaranteed to be free from electrical and mechanical
defects for a period of one year from date of shipment

grounding. . . . .
from the factory, provtded all Instructions are complied
c. Connect the iacks marked- OUT" of channel with fully. In case of damage, it is essential that you
A and B to the corresponding input iacks of the carefully repack the unit and return it to the factor for
power amplifier or preamplifier or to the earphones. repair. Our guarantee is voided if the assembly has been
(Parallel the outputs for monaural earphones). If it is subiected to unreasonably rough handling.
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CIRCUIT DIAGRAMS CIRCUIT DIAGRAMS
OF POWER SUPPLIES OF PREAMPLIFIER SECTION

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The M61 Preamplifier has been designed to operate
satisfactorily with most magnetic phono cartridges. How-
ever, certain cartridges having very high output may
cause overloading and distortion.

This distortion can be eliminated by using a simple
resistor network at the input of the preamplifier. See
Optional Network."

The network must be used in both channels and can be
inserted inside the preamplifier case or can be made up
as an external attenuator between the phono cartridge
and the preamplifier inputs.

OPTIONAL NETWORK