Shure M-64, M-642-E Service manual

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

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).

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